$Earings and Bearing Metals

$EARINGS AND BEARING METALS

A TREAT I SE D EAL ING W I TH VARI OU S T Y P E S F PL I B I G THE C OMP O S I TI N O A N EAR N S , O S AND P P I OF B I G M L M H D RO ERT ES EAR N ETA S , ET O S O F IN S U R I NG PR PE R L U B I C I O AND O R AT N, I MPORTANT FAC T ORS GOVERNING THE DE S IGN OF PLAI N B E ARI NGS 0

FI R S T E D I TI ON

FIR S T PR I NTI NG

NE W Y ORK THE I NDUS TRI AL PRE S S

L o o : TH E MAC HI NE R Y P U B L I S HIN G c o L td nd n . 1 921 En i g neering

C o r i h t 1 9 2 1 T he I d s tr i a l P r es s P bli sher s o f M A C HI N E R Y p y g , , n u , u , 1 40- 1 48 L a a f y ette S tr eet, N ew Y o r k C i ty PRE FACE

FEW subj ects related to the design or construction of ma chinery are of greater importance than the subj ect of bear ings . All classes of mechanisms have bearings of some kind and bearings that are properly designed and con structed are a necessity . As every experienced mechanic knows , a poor hearing may tie up a machine or even cause ' an entire plant to shut down temporarily . Owing to the importance of this subj ect , designers and mechanics in general should understand the fundamental principles gov erning bearing design and should know what approved types are in common use on different classes of machinery .

This treatise deals exclusively with plain bearings , ball and roller bearings being covered in another bo o k of this i n series . The types o plain bearings illustrated connec f . tion with the following chapters were selected to show how i designs are mo d ﬁed to suit different conditions , and also practical methods of arranging bearings to insure adequate lubrication and thorough protection against the entrance of any foreign material liable to inj ure the bearing sur e faces . The designs illustrated were taken from actual pra tice and have proved satisfactory when properly con structed and applied . This treatise contains , in addition com to the features mentioned , condensed information on positions of various bearing metals , their properties , the classes of service to which different bearing alloys are adapted , and the general methods of procedure in design i ing plain bearings to meet different service condit ons . CONTE NTS

Types of Plain B earings

B earing Metals

Methods of L ubricating B earings

Design of Plain B earings J J J J J J

BEARINGS AND BEARING METALS

CHAPTE R I

TYII’ ES OF PLAIN BEARINGS

B EARI NGS ’ may be divided into two general classes o ur na l j ournal bearings and thrust bearings . In the j bear ing the load acts a t right angles to the axis ; such bearings are also termed r a di a l bearings . In the thrust bearing , the B load acts parallel to the axis . earings may a lso be divided into two classes according to the manner in which the bear ing surfaces are in contact with each other . Ordinary bear b ings have a sliding contact , whereas all and roller bearings s s have a rolling contact . In this treati e , bearings with lid ing contact only will be dealt with .

n st a b Bea r n s S olid a d Adj u le i g . In the simplest form of ﬁt bearing , a cylindrical shaft s into a hole in the part which forms the support for the shaft . In a bearing of this type , there 18 no provision for the taking up of the wear between the shaft and the bearing . For this reason , a bushing or lin ing is generally used in the supporting machine part into

ﬁts . which the shaft When this bushing becomes worn , it can easily be replaced . Frequently bushings of this type are made tapered on the outside and ﬁt into a tapered hole in the supporting frame . The bushings are split and , as the hole in the b ushing wears , means are provided for pulling the bushing into the tapered hole so as to reduce the diam eter of the hole . In other cases , the bushings are cylindrical , a so but the whole b e ring is split , that , when wear occurs , one-half of the bearing can be tightened down to restore proper conditions . 0 S eIf- n n Bea r n s alig i g i g . Whentorque is applied to a shaft nd a the j ournal begins to move , the bearing should be so “ 2; PLAIN BEARINGS

wi ll adj ust itself to the j ourna l a nd equal l vm the entire bearing , thus g g an oil ﬁlm of uniform thickness in a line parallel—with the shaft . Sma ll bearings may not require ,this self aligning feature , the limits used being accurate enough to give uniform

alignment ; but larger bearings , built from a number of as

- sembled parts , should embody this self aligning principle .

- - Y ears ago , engine builders adopted a ball and socket seat for s now this purpose . Some manufacturer prefer that design , a e and , for certain classes of appar tus , there may be n ed for some such arrangement ; but for the small limits of deﬂec tion and the higher speeds now used in machinery bearings An generally, a simpler arrangement is used . annular ring is turned in the center of the bearing shell for about one ﬁf h t of its length , and this rests upon a corresponding sup p o rt in the housing ; the bearing ring extends down over

' the sides o f the su pp o rt to take up the thrust due to end

play . This is a very effective and simple arrangement and is the type of support referred to when self- aligning bear s eci ﬁed ings are p in electrical machinery , for example . The i o other type s used for s me designs , when larger limits of — “ self alignment are necessary , and is known as a spherical ” - a seat self aligning be ring . This typ e is especially used for

- - line shafting ; it has a self aligning ball seat on the bearing ,

ﬁts - which into a ball seat of the bearing box .

ha ra ct r st cs of P n B r C e i i lai ea ings . Plain bearings ha ve been developed to meet the requirements of many different conditions of service under which shafts and spindles are r e to operate In all plain bearings there is surface con l quired )

tact between the shaft and the bearing, and in order to pro vide for the efﬁci ent transmission of power without exces

sive frictional resistance , wear, and tendency of the bearing

to give trouble through heating, a constant supply of clean e lubricating oil must be deliv red to the bearing, and this lubricant must be suitable for the conditions of bearing

pressure , speed of rotation , etc . The effect of a lubricant

c - - is to prevent dire t metal to metal contact . S ome a uthori ties explain this action by comparing the lubricant to the

. W balls in a ball bearing here this comparison is made , it PLAIN BEARINGS

is j usti ﬁed on the basis that the lubricant consists of a mul ti tu de of small globules of oil which roll between the shaft ' - - and its bearing, thus preventing metal to metal contact

and greatly reducing frictional resistance .

Plain bearings are made in a great variety of designs , according to the conditions o f service under which they o p n a er a te, and as many of the best desig s are found on m chine

tools , bearings for this class of service will be featured in a s this book . As rule , when bearings are u ed to support the consi d spindles of machine tools , where the presence of any crable amount of lost motion would result in ina ccuracy of n work produced by the machines , mea s of adj ustment are provided to take up any l o st motion that devel ops as a result

of wear in the bearing . In the detailed descriptions of dif ferent la i n 'bea r i n s types of p g , the manner in which design ers have worked out means of compens ating for wear will

be explained .

st a b Be r n s fo r M c ne T ndl s Adj u le a i g a hi ool S pi e . In de signing the bearings for carrying the spindles of machine tools , it is very important to provide m eans of constantly maintaining a ' tight fit between the spindle a nd its bearing ff m boxes , in order e ectually to eli inate chatter and vibra tion . It is evident that any lost motion in the bearings will seriously affect the accuracy of work produced on the ma chine and the perfection of fini sh which it is possible to oh No tain on the work . t only must the bearings be a perfect fit at the time the machine i s new , but provision must also be made to compensate readily for any wear which develops e aft r the machine is placed in service , s o that it will con tinne to produce work of the required degree of a ccuracy .

To meet the requirements of this service , some form of tapered bronze bearing has been quite generally adopted as n a standard spindle bearing constructio , although various mo di ﬁca ti o ns of this general form of design have been worked out by di fferent ma chine tool builders to provide for making the necessary adj ustment for wear . These mo di ﬁ cations may be made to meet the requirements of different conditions of s ervice for spindles which are m ounted in a vertical or a horizontal p osition , or they may be worked out 4 PLAIN BEARI NGS simply to meet the individual opinions of different design

ers . In the following discussion , there are presented de scr i pti o ns a nd illustrations of different well - known forms of adj ustable spindle bearing designs , which have been found to give satisfactory service . r n G rinding Wheel S pi ndle Bea i gs . In o rder to give satis r o factory service , the spindle of a grinding machine must tate without an appreci able amount of Vibration ; otherwise

F i 1 . D g. es i gn o f S p ind l e B ea r ings f o r E xt e rna l G r ind ing a c e s o w P r o s M h in , h ing v i i o n m a d e t o c o m p ens a t e f o r W e a r a nd M et h o d o f L u b r i ca t i o n

w o chatter marks ill appear on the w rk . It is safe to say, perhaps , that in working out the design of the average grinding machine , more time is given by the designer in de velopi ng a satisfactory form of spindle bearing construction and in modifying this design to overcome trouble which is ﬁr s experienced when the t machine is placed in s ervice , than in producing s atisfactory results in any other part of the

. 1 mechanism In Fig . there is shown the standard type of grinding wheel spindle bearing which has been adopted for use on external grinding ma chi nces built by the

C o . Landis Tool , of Waynesboro , Pa . The bronze bush ings A are assembled in the housings in s uch a way E I NG 5 (PLAI N B AR S

that expansion and contraction , due to changes in tem p er a tur ey do not in any way affect the transmission ef fi ci ency of the bearings ; and compensation for wear provided by the tapered form of the bushings enables ‘ f eli mi all lost motion to be taken up , thus ef ectually nating Vibration and enabling the grinding machine to pro l A du ce p er fect y accurate work . ttention is called to the fact that adj ustment for wear in the front and rear spindle bearings is made independently, s o that if only one bear

ing requires adj ustment , this can be done without touching the other bearing . On these bearings , lubrication is pro

- - vi ded by individual sight feed oil cups , from which a sup ply of oil is delivered to a reservoir E beneath each of the

wi ks k e o bearings . Felt c ta oil from these reserv irs and

carry it up to the bearings , the wicks F being held in con tact with the bearings by means of compression springs . It will be seen that each reservoir is provided with a threaded ' H w plug , hich may be r em oved to drain out dirty oil and ﬂu sh the bearing with kerosene before the plugs are r e placed and a fresh supply o f lubricating oil is delivered to ‘ D the reservoir . rains G prevent the possibility of reser

vo i r E v r ﬂo i n ﬂ o o i n - r s o e w g and d g the bearings . Oil di st ib uti ng grooves I are cut in the j ournals to facilitate the uni

wa form distribution of o i l. The y in Which these spindle

bearings are adj usted will be apparent from the illustration . B ronze bushings A are a press ﬁt in the housings , and

j ournal sleeve B is ﬁtted over the back end of the spindle .

The thrust load is carried by steel thrust washers C . When it is necessary to compensate for wear in the j ou r na l bear o L ings , this is d ne by releasing collar J and tightening to draw the front bearing into its box to take up lost motion ;

similarly, lost motion in the rear bearing is taken up by K L releasing collar and tightening , which forces sleeve B E into the tapered bo . ach division on collars J K, “ bronze x and L gives inch of adj ustment on the diameter of the bea—rings . f n n r s Sel alig i g S pi ndle Be a i ng . Features of particular i n ter est in connection with the design of bearings for the

e - B whe l spindle of a rown Sharpe grinding machine , 6 PLAIN BEARINGS

2 shown in Fi g. , are the provisions made for lubrication and for the automatic alignment of the bearings with each

- - other . It will be seen that a sight feed oil cup is provided at the top of each bearing housing, from which lubrica nt is delivered to the annular channel A cut in the inside of sleeves D . Oil runs around this channel and is absorbed by B w a felt packing or wick , hich is contained in a slot cut through the bronze bearing box on the under side of the sha ft . This felt packing is kept constantly saturated with

d F i . 2 A t r m e o f B ea r C o s t r ct o f o r r g . no h e Ex a p l ing n u i n G in ing M a c h ine S p i nd l e

As fl at . oil, and is held against the shaft by a spring the x shaft revolves in the bearing bo , the felt distributes a uni ffici entl form film of oil over the shaft , thus e y lubricating the bearing .

To assure accurate alignment between the two bearings , each of the bronze boxes C is carried in a sleeve D that is machined to a spherical form on the outside in order to ﬁt into a corresponding spherical seat in the bearing housing . When a straight shaft is put through bronze bearing boxes m C , it will be apparent that the bearings will align the selves accurately on account of the ability of the spherical - seated PLAIN BEARINGS 7

D Th sleeves to move as required in the bearing housings . e bronze bushings C in these bearings are tapered on the out side and bored straight on the inside ; this is not quite so

F i 3 . g. B ea r ing f o r T a b l e o f R o t a ry S u rf a c e G r i nd lng a c e s o w et o d f a t m t M h in , h ing M h o u o a i c a l ly co m pensa t i ng f o r W ea r usual an arrangement a s that of bronze b oxes which are bored to ﬁt a tapered j ournal on the shaft they a r e designed ' to ca r r . C y These boxes are split , and in order to compen 8 PLAIN BEARI NGS

sate for wear , it is necessary to push the tapered outside e D surface of the b ox into the tapered s at in sleeve . The boxes and a dj usting nuts have beveled ends to keep the

D . E bearings expanded in sleeves First nut is loosened , and then nut F is tightened sufﬁci ently to force the bronze box into sleeve D and cause it to contract in a way made possible by the split construction . After the d esired adj ust

e F E ment has been obtain d by tightening nut , nut is again

i t ghtened against the opposite end of the bearing box , thus

locking the box securely against further end movement .

Fi . g 4 . S t r a i gh t C yl ind r i c a l S p ind l e B ea r ings p r o vi ded w i t h M ea ns o f c o m p ens a t ing f o r W ea r — e f d ust n V rt S l a j i g e ic a l Beari ng . The upper bearing for the table or chuck of rotary surface grinders built by the

P - M M o ersons Arter achine Co . , of Worcester , as s , is pr vided with means of automatically taking up any wear in the

bearing as fast as it develops . The way in which this is accomplished will be readily understood by reference to Fig . 3 , where it will be seen that steel colla r A is shrunk on the upper end of the spindle and that this collar is tapered o n the outside to ﬁt a bronze bearing box of corresponding form . This steel collar A acts as a wedge in order to keep a the bearing ccurately centered , although the angle is such gLAI N BEARINGS 9 ' that the bearing runs quite freely and with very little fric

o tion . There is said t be absolutely no chance for side play in this spindle bearing which would cause the work - table or

magnetic chuck to get out of alignment in any direction . Collar A a nd the bronze box in which it runs are arranged to form an oil reservoir fr om which a constant supply of

lubricant is delivered to the bearing, lubrication being facili tated by spiral grooves in the taper collar which carry the lubricant and distribute it uniformly over the rubbing sur

faces . r Adj ust able Be a ri ng Bo x o f St raight Cylindric a l Fo m . Still another form o f adj u stable spindle bearing box is 4 B co nstr uc shown in Fig . . This is another rown Sharpe

tion , which has been designed for use in headstock spindle f bearings . It will be seen that this box dif ers from any of the designs which will be shown in this chapter in that it is

of straight cylindrical form on both the inside a nd outside . The method of making adj ustment of the ﬁt of this box on the spindle will be best understood by referring to the de A tailed view of the box shown at , where it will be seen that ext end l a split s a l of the way along one side . Two dovetail slots B are machined in this split secti o n to accommodate screws and beveled nuts or sleeves which may be tight ened or loosened in order to expand the opening in the box or cause it to be contracted through pressure applied by the

cap of the bearing housing . Reference to the end view will show that there are two screws C which hold the cap of the b ea r i n 'ho u si n g g down on top of the bronze box , a nd when fit it is desired to secure a tighter of the box on the spindle , this result is accomplished by fir st backing away the screws in the sleeves in slots B and then tightening up the screws C on the cap of the bearing housing . In this way exactly fit the required for the bearing box may be obtained , and after the bearing has been in service , co mpensation for wear may be accomplished by further a dj ustment of screws C and the screws which adj ust the s leeves fitti ng into B slots .

x m l n l r s n E a ples o f Mil i ng Machi e S pi nd e Bea i ng De ig . For supporting the spindle of the vertical milling machine 1 0 PLAIN BEARINGS

M o . . built by the Ga rvm achine C , Spring and Varick Sts ,

New Y ork City , the following construction has been adopt

e 5 ed : At the lower end of the spindl , Fig . , there is a bear ing box A which is bored to a taper corresponding to the tapered j ournal on the spindle , to provide means of taking

i . D r rt c M PIIi n F g 5 . es i gn o f A dj u st a b l e B ea ings f o r V e i a l g a c e s o w ea s o f C o m e s a t f o r e a r M h in , h ing M n p n ing W

up any wear that may develop . It will be seen that the spindle is threaded along the straight portion immediately above the tapered j ournal to receive a threaded collar B which provides for holding the spindle up . When lost mo tion develops it is easily tak en up by simply pulling the spindle up int o the tapered bearing by tightening collar B .

To provide for making this adj ustment , it is necessary to I’ LAIN BEARINGS 1 1 I face o ff the soft washer between bearing box A and the fl a n At S pindle ge. the upper end , the spindle is straight and is carried in a bushing C which is bored straight on the inside and turned to a taper on the outside , this bushing be ing secured to the spindle with a Woodruff key so that it is a tight fit . On the outside , bushing C is turned to a suitable fit D C taper to bearing box , and bushing is threaded at the lower end and furnished with a collar E which provides for maintaining a tight fit between bushing C and bearing box D B ll . co a r E y screwing up , provision is made for taking

F i . 6 A d t B r e S d B a r r d w t g . j u s a bl e o nz p in l e e ing fu ni s h e i h M e a ns o f c o m p e ns a t m g f o r W ea r a n d P r o vi s i o n f o r C o nt inu o u s L u b r lc a t i o n f r o m a R es e r v o i r up any wear which develops in this bearing after the ma chine is put into service . It will be apparent that the use

e of bushing C , which is k yed to the spindle , is a substitute for having the j ournal made an integral part of the spindle , as it is at the lower end . The reason for having the upper j ourna l in the form o f a bushing keyed to the spindle is that

this greatly facilitates the work of assembling the machine . Collars B and E are provided with split nuts to hold them la ce fter in p a making the settings .

Pr v s n fo r l a n n B r n s . 6 o i io C e i g ea i g Fig . shows a form of spindle bearing construction which has been a dopted as one of the standards in building machine tools made by the Gar . v i n M o b achine C . It will e apparent from the illustration 12 PLAI N BEARINGS that in working o ut this design provision has been made for c e supplying the bearing with lubri ant from r servoir A , s e which extends around the out id of the bearing box . A supply of o i l is delivered into this reservoir through tube B and ﬁnds its way from the reservoir to the bearing sur face through holes which connect with oil - grooves cut on the inside of the

e b aring box . The reservoir is cleaned out by Opening drain pipe C to allow the

dirty oil to run out , after which the bearing is ﬂ u sh cd with kerosene before closing drain C and ﬁlli ng the reservoir with a supply

of fresh oil . It will be seen that the spindle is threaded on the straight portion di r ectly to the l eft of the ta

e per d j ournal , to provide for drawing the s p i n d l e into its tapered b earing box when it becomes necessary

to compensate for wear . B efore this adj ustment can

be made , soft washer G

must be faced o ff . Collar D , by means of which this S adj ustment is made , is plit

M a chi ner y at one side and furnished E w th a clamp screw , so F i i g. 7 . A dj u s t a bl e B ea r ings de s i gne d f o r V e rt i c a l S p ind l e that when the bearing has P r o fi l i n g M a c h i n e been adj usted to obtain the e e ﬁt E d sir d , screw is tightened to clamp collar D ﬁr mly in

the exact position to which it has been set . In most ma chine tool bearings , provision must be made for carrying a thrust load in addition to the normal radial load which om c es on the bearing . In the present case , this result is

14 PLAI N BEARINGS

ﬁt outside , bushing E is machined to a taper to bronze bear e e e d ing box F accurately , and wh n it is n cessary to mak a j ustment to compens ate for wear, threaded collar G is tight

a C ened . It will be app rent that both collars and G are split o n o ne side and furnished with binding screws to p r o vide for securing the collars in the desired positions after h the required adj ustment a s been made .

ns t o a r m r ss n a r n o Co mpe a io n f r We by Co p e i g Be i g B x. 8 o In Fig . there is shown a different meth d of providing compensation for wear in a tapered bronze S pindle bearing

box . This construe tion is used on the 2 Garvin No . uni versal milling ma

chines . At the front

end , the spindle is fur ni shed with a bearing box of the same gen eral design as those which have already

been described , but at

the rear end , as will be

' F i . 9 . B e a r i n s s i ned s o t a t g g h seen , the bronze box is go m p e ns a t I o n f O P ese a r i 8 a c c o m p li s hed by d r a w ing S p ind l e S pll t and ﬁtted to the i nt o T a p e r ed B o x s traight end of the spindle , this box being tapered on the outside to engage a bushing in the machine frame with which it remains ﬁxed in contact . This necessitates an entirely different method of adj usting the box to ‘ afford compensation for wear , and such adj ustment is obtained by tighten ing threaded collar A to provide for pulling the ta

pered bearing box into the bushing in the machine frame .

When this collar is tightened to pull the bearing b ox into the tapered bushing, the bronze box is compressed against

o u r nal the straight j on the spindle , thus taking up any wear

o which may have devel ped . Attention is also called to oil B hole , which delivers a supply of oil into reservoir C , formed in this bearing box to provide a liberal supply of PLAIN BEAR INGS 15 oil ; the oil ﬂ ows from the reservo ir through oil-holes con necti ng with grooves machined in the bearing surface of the box to pro vide for distribution of lubricant over the

- bearing . The same arrangement of an oil hole and oil reservoir in the bearing box is provided at the front end of the spindle . Co mpe ns atio n fo r We ar by Drawing S pi ndle i nt o Ta pered

Bo x. Fig 9 shows an example of the design of bearings for n a machine tool spi dle , where the j ournals are directly sup ported by tapered bronze boxes at both ends . It will be seen that at the front end of the spindle ( which is the left hand end in this case ) a tapered bronze box A is provided c m which is threaded on the outside at both ends . To o pen sate for wear which may develop in these bearing boxes , the r : B method of p ocedure is as follows Threaded collar , car ' - o f ried at the right hand end the spindle , is tightened to d r aw the entire spindle , and hence the tapered bearing at this end o f the spindle , back into box C to compens ate for any lost motion which may have developed as the result of wear . When this result has been obtained , a corresponding A adj ustment must be made on box , the procedure being as follows : J a m nut B is loosened and the rear step plug be hind the nut is slacked away , after which threaded collar D at the front end of the spindle is loosened and collar E is then tightened to draw the front tapered bearing b ox up to a snug ﬁt on the j ourna l ; this also pushes the entire spindle e back into the rear tapered b aring C . When this result has been obtained , collar D is tightened to hold the box in ex a ctly the position in which it has been set . Then the rear step plug is carefully adj usted against the rear end o f the spindle and locked by a j am nut B . This is another bear

M o ing design used by the Garvin achine C .

st - r a n B a b tt nd e B r n s C a i o n d b i S pi l ea i g . E xperience ha s shown that very satis factory service is obtained from a hard

- steel j o u r na l running in a cast iron bearing . With such a combination , it is found that the cast iron has a tendency to become glazed on the surface in such a way that the co efﬁci ent of friction between the bearing and its j ournal is PLAIN BEARINGS

tr a nsmi ssi o n efﬁci enc very small , thus making the y of the bearing correspondingly high ; also a bearing of this kind is so hard that wear becomes almost a negligible quantity .

1 i s s In Fig . 0 there shown a type of pindle bearing con struction which has been adopted as a standard by the R .

L B lo nd M C o . K . e achine Tool , of Cincinnati , Ohio , in build t ing lathes , milling machines , and cut er grinders . This consists of a cast-iron box at the front end and a babbitted

Fi . 10. a m e o f S ln d le C o s t r ct o s ed f o r L a t es g Ex p l p n u i n u h , a c es nd tt r r de r s w ere ro t M i l l ing M h in , a C u e G in , h F n B ea r ing i s o f C hllled C a st I r o n a nd R ea r B e a r ing i s l ined w i t h B a bb i tt

box at the rear end of the s pindle , and the results obtained by this combination ha ve proved so satisfactory in practice h t at a detailed description will be of interest .

- The spindle is made of 50 point carbon steel , and over this there is pressed at the front end a hardened steel bush ing made of Shelby seamless tubing . In making this bush ing , the blank is cut o ff and annealed , after which it is bored , turned , and carburized ; then it is necessary to round up the bushing to remove any distortion which has been PLAIN BEARINGS 17

- e produced during the heat treatment , after which it is r

- heated and quenched in water to make it glass hard . After hardening, the bushing must show a sclero sco pe hardness 80 of degrees , and those which fail to f ulﬁll this test are

- heat treated aga in . The hardened bushings are ground on

n - the i side and rough ground on the outside , after which they are again tested for hardness before being pressed on the spindle . The fit o f the bushing on the spindle is so adj usted $ ’ that from seven to ten tons hydraulic pressure is r e

o s quired t pu h it into place , after which the bush ing is groun d to standard size . The cast iron for the bear ing is cast against a chill to make the metal dense

- M and cl o se grained . ention has already been made of the fact that this hardened steel j ournal is carried in a cast—ir o n bearing box which is a n integral part of the m e b ain headstock casting . This eliminates an xtra j oint e

- f tween the bronze box or a babbitt lined bearing, and af ords

a more rigid construction , a lthough the work of scraping the cast- iron spindle bearing to an accurate ﬁt and perfect

i ob alignment is a d fﬁcu lt j , calling for the s ervices of an ex

er i enced A - p mechanic . cast iron bearing of this type must be ~more accurately ﬁni shed than either a babbitted or a

- d bronze bushed bearing , becaus e no depen ence can be placed upon the spindle wearing itself to a sa tisfactory ﬁt after the machine is placed in service ; the bearing must

e ﬁt properly before the machine is started . Sev ral years

M o ago the R . K . LeBlo nd achine Tool C . built four trial head -istocks equipped with the fo llowing combinations of j ournals a nd bearings : ( 1 ) Cast - iron bearings and soft steel spindle ; ( 2 ) bronze bearings and soft steel spindle ; ( 3) babbitted bearings and soft steel spindle ; and ( 4 ) cast iron bearings and ha rdened steel spindle . L athes with spindles of these types were kept in constant

use on wo rk of the s ame general character , and when ex

e a mi ned, the condition of the hard ned steel j ournal running

- in a ca st ir o n box was found to be the best , neither the spindle nor the box being worn to a n appreciable extent

and the grinder and s craper marks still being visible . The 18 PLAIN BEARINGS combination of a soft steel j ournal and bronze box w a s in good conditi on , but the j ournal was slightly ridged in the

- wa s a center . The soft steel spindle in a cast iron box p i l p r ec a b y worn , but the soft steel spindle in a babbitt box

- L was in ﬁr st class condition . There are lathes in the e B lond shops at the present time in which hardened steel spindles have bee n running in cast- iron boxes for about twelve years Without any adj ustment having been neces sary . . The wear is so slight that it can scarcely be meas i m u r ed With the most delicate instruments . It is very portant , however , to have the combination of a hardened

- steel spindle and cast iron box , as a soft steel spindle and a cast- iron box is much less satisfactory than a soft steel

- spindle and either a bronze bushed or babbitted bearing .

At e L B lo nd e the r ar end , the spindle of e lath s , milling machines , or cutter grinders is supported in a babbitted bearing . It will be seen that the seat for this babbitted bearing is dovetailed and the babbitt is poured , after which the bearing is bored in p o sition . No attempt is made to

E e peen the metal . xperi nce has shown that wear on the back bearing in a headstock of this c onstruction is propor ti ona te to the wear of the front box with its hardened steel

- j ournal running in a cast iron bearing . Practically no a t tention is required by bearings of this form a fter the front bearing has run for a su fﬁci ent timeto enable the cast iron

to become glazed . The metal becomes so hard on the sur “ ” face that it can scarcely be touched with a scraper .

ess B a r n s Oill e i g . The advantages of the oill ess or self lubri cating bearing for many classes o f service have led to f the development of several dif erent types , each of which doubtless ha s its advantages when applied under suitable conditions . One type consists of wood impregnated with ‘ a r a ﬁin o wax , oil or p . Another is made of br nze and has

a e gr phite ins rts . Still another type is formed of graphite impregnated with some bearing metal such as a white metal

alloy or bronze .

“ One type of oilless bearing has on the bearing surface , n symmetrical grooves of various designs , depending upo PLAIN BEARINGS 19

the service for which the bushing is intended . These

a grooves are packed solid by means of hydr ulic pressure , with a special hard graphite lubricant . When the bush n fin ings are once installed a d in use , e particles of the graphite lubricant are distributed o ver the entire bearing surface of the bushing . Ample lubrication is provided for s almo t any form of bearing contact , whether the movement be oscillating , vertical , horizontal , or full revolution . Ow ing to the sci enti fic design of the graphite gro oves which fi ts them for the particular service required , wear is r e

d - duce to a minimum . The design of the graphite packed gro o ves varies in different bushings because some bush f ings are subj ected to dif erent kinds of contact from others . e Th se bushings are suitable for use in machine tools , coun ter sha fts li n sha ft , e hangers , electric motors , etc . , but , a l “ ” r om though they are styled oilless bearings , it is ec mended that about 2 5 per cent of the volume of oil which would be required to operate efﬁci ently an ordinary plain bearing of the same size should be applied to these oilless bearings . However , in the event of failure on the part of the attendant to give the bearing the required oil , this lack

' f n i o a tte t on is not so likely to result disastrously , a s would

- be the case with an ordinary bronze bushed bearing . Another type of oilless bearing consists of a bushing

made of either hard maple or iron wood , which is thor o ughly impregnated with a mixture of graphite and other

a r lubricant by a special treatment . These e more truly “ ” a oilless bearings than the type th t has graphite inserts , because when the bearing is in operation a slight increa se in temperature resulting from fricti on ca uses the bearing to exude some of the lubricant with which it has been i m efﬁci ent p r egna ted, thus providing for transmission of a power . These bearings are especially ad pted for use in loose pulleys ; and in many cases they are run without any

provision for lubrica tion . S ome users prefer to drill the

- usual oil hole in the hub of the pulley and in the bushing,

‘ i ded so that a little o il can b e a d from a squirt can , and very satisfactory results were obtained where the bushings were 2 0 PLAIN BEARINGS

used in this wa y. They must be properly supported to pre

f o vent splitting, although with suf icient support these w od en bushings have ampl e strength to resis t any crushing load to which they will be subj ected when used in loose pulleys and similar positions . Still another type of oilless bearing consists of graphit e f bushings made o the required sizes , and impregnated with white metal or bronze to produce what is known as “ graph ” alloy . The metal used for impregnating the graphite de pends upon the class of work . All parts such as shaft bear ings are impregnated with a white - metal alloy or babbitt o metal of special comp sition . The parts us ed in connec tion with electrical apparatus are impregnated with a cop per alloy which is also utiliz ed for such parts as steam tur bine packing rings , etc . , Which must withstand high steam temperatures . The use of copper for the electrical work is

essential because of its electrical conductivity . The extent to which the graphite is impregnated with the metal is indicated by the fact that the weight of the graphite is pound per cubic inch , whereas the weight of the metalized product is pound per cubic inch when impregnated with babbitt , the increase of weight due to the metallizing process being practically 1 50 p ei “ ” 60 b cent . The metal in graphalloy is about per cent y i ﬁ 2 . s ec c weight , or 5 per cent by volume The p gravity is

4 and the compressive strength , approximately

“ ” o pounds per square inch . Graphall y is not inj ured by d the application of lubri cant . In fact , the use of an applie lubricant is recommended when the bearings are used for rather heavy service

At the present time gr -a pha lloy in the form of bear ings is applied to light - duty machinery operating at high speeds and to heavier service when the speeds are relatively a pli low . Its use is recommended particularly where the p

di fﬁcu lt cation of oil is either obj ectionable , , or likely to be

neglected . These bearings are commonly applied to loose

e , pulleys , v rtical shaft bearings , conveyors textile machin

2 2 THRUST BEARINGS center taking the end -thrust of a cut on a piece held b e

- tween the centers . In general , however , the end thrust is ﬂ a t taken by a large ﬂ a t or nearly surface . When this is

the case , several considerations present themselves which must be given due attention by the machine designer . As sume that the ﬂ a t end of a vertical cylindrical shaft carry ing a weight or otherwise subj ected to pressure is sup ﬂ t ported by a a surface . Then , if the shaft rotates , the velociti es of points on its end surfac e at different radial distances from its axis , will vary . The velocities of the

om a r i o h points near the outside will b e, in c p s , very high ,

while the velocity of a point near the center will be low .

Ou account of this variation in velocity , the wear on the end surface of the shaft and the thrust surface of the bear

e ﬁ ing will be considerably unev n . If the parts are well t ted together when new , so that a uniform pressure i s pro duce d all over the end of the shaft and bearing, then the outer parts of the bearing surfaces will wear away most

rapidly . This again increases the pressure at the center , Which sometimes may become so intense as to exceed the

ultimate crushing strength of the material . The unequal wear of the surfaces of thrust bearings is one of the most

di fﬁcult problems meeting the designer of machinery of. which such bearings form a part . h T e Schiele C u rve . E xperiments carried out by Schiele show that the wear is theoretically along a curve called the tr - a ctr i x . If an end thrust bearing is made of a form cor responding to the Schiele curve then the wear in the di r ec tion of the axis of the thrust shaft will be uniform at all points ; but while this curved form would be theoretically correct it has been shown in practice that nothing is to be gained by the use of bearings having this complicated

shape . m l t e Be r n s f r t Dut . Si p S e p a i g o Ligh y For light duty, e h 1 1 14 simpl step bearings of t e types shown in Figs . to

meet the requirements . The intense pressure at the center and the consequent unequal wear are partly avoided in the THRUST BEARINGS 2 3

bearing in Fig . 1 1 by cutting away the metal at the center

of the shaft, as shown , leaving an annular ring which takes

1 a ll the thrust . This procedure s advisable in step bear

i fﬁcu lt ings . Another d y met with in bearings of this type

is the question of lubrication . If the speed of the shaft is high , the centrifugal force tends to throw the oil out from o the center . Special pr visions must then be made for again

returning the oil to the center , as otherwise the bearing 1 1 would wear dowri rapidly , become heated , etc . In Fig . , a simple method is shown for automatically returning the

- oil to the bearing surfaces . An oil passage is made from

n Ma chi ew,M Y.

s 1 1 a nd 12 . S m e D es s o f S t e B ea r s F i g . i p l i gn p ing

the chamber A fo rmed around the shaft to the center of the n shaft at the bottom . When the channel a d chamber are once ﬁlled with oil this oil will continue to ci r culate a uto , w ma ti ca lly ; it will be drawn in at the bottom , be thro n ﬁn outward by the centrifugal force , d its wa y into the

ﬁna ll chamber A , and y, through the channel , return to the

center of the bearing .

When a bearing for heavier duty is required , the design A n 12 . shown i Fig . is quite commonly adopted number of disks or washers are placed between the end of the

thrust shaft and the supporting bearing, in order to intro

duce a number of wearing surfaces , instead of having the 2 4 THRUST BEARINGS

end of the shaft a nd the box take all the wear . Due to the fact that the series of washers introduced p ermits of a

s lower speed b etween each pair of wa hers , the wear is quite materially reduced . Should the pressure cause any two washers to heat and bind , the frictional resistance between them ceases , as one washer is free to follow the motion of the other , and the oil will have an opportunity to

o ff get between the surfaces and cool them .

be A hole may , and generally is , drilled through the

h 12 a n centers of the was ers , as shown in Fig . , d the same 1 method for continual lubrication , as shown in Fig . 1 , may E be used to advantage . very alternate washer is com monly made of hardened tool steel or case -ha rdened ma

e o chine steel , while the others are mad of br nze . This com e bination provid s for good wearing qualities . If the thrust shaft is made of soft machine steel , and the box of cast n iron , the top washer is often secured to the shaft , a d the bottom washer to the box , so that all the wear may be

r e concentrated upon the washers , which can easily be placed . 13 In Fig . is shown an improvement on the bearing in 2 Fig . 1 . This construction is recommended , in particular, in cases where the shaft and its bearing box cannot be s properly aligned with one another . The wa hers have

spherical faces , being alternately convex and concave . They are slightly smaller in diameter than the bearing box into

o o r which they are inserted , s o that they may have an pp tuni ty to adj ust themselves to a perfect bearing on each

other , and thereby make up for the differences in the align ment of the thrust shaft and bearing box . Another typ e of thrust bearing for loads which are not 14 excessive is shown in Fig . . It is a well established prin ci ple that it is better to take the thrust of a be as near a llo the o the shaft a s the load to be carr i ed yz . center i ‘ will ‘ ' ‘ ’ I ‘ ’ the The fg her awayfi brﬁ thecénter support is , the great er is the motion a nd the greater is the r etarding effect of the

, friction . The thin convex washers used are of tool steel THRUST BEARINGS 5

hardened , and , although the bearing between them is very

small , their strength and hardness is such that they are c apable of standing a considerable pressure , although not

‘

o . so great a one , proba bly, as the other forms sh wn in Figs 1 1 12 1 di fﬁcult , , and 3 . In this bearing, also , there is no y neces in keeping the surfaces well o iled , since all that is

sary is to keep the chamber well ﬂooded with oil .

ﬂ a As already mentioned , t thrust bearings should be made of an annular form . It is good practice to make the

- x er i inside diameter one half of the external diameter . E p

ﬂ a t o ments made on piv t thrust bearings , three inches in

F . r D e o f S t e B ea r s i gs 13 a nd 14 . Ot h e s i gns p ing

d o fﬁ i n iameter, indi cate that the c e c e t of friction between

- a steel pivot and a manganese bronze bearing, properly

o lubricated , using two radial oil gr oves only , varies from

at 50 revolutions per minute , to an average of a t 350 revolutions per minute . If four radial oil grooves

o are used instead o f tw , the friction is approximately i l ﬁlm o . doubled , due to rupture of the

st B a r n s Lo a d o n Th ru e i g . The load that ma y be safely l carried by a thrust bearing varies with the velocity of the

rubbing surfaces . The accompanying table may be used as a guide in designing bearings in which the shaft is made from wr ought iron or steel and the bearing from bronze or 2 6 THRU ST BEARINGS

o . brass , and which have ample lubricati n In general , it is possible to use bath lubrication for thrust bearings , that is , the running surfaces a r e submerged constantly in a bath i l of o . If the sha ft is made from cast iron running on bronze or brass bearings , the values in the table for allow

o - able pressure sh uld be only one half of those given . In designs where the motion is slow and heating canno t well r n result, as in pivots for swing b idges a d similar constr uc 4 000 tions , pressures up to pounds per square inch are per missible .

A llo w a ble P r ess u r e i n P o n ds er S u a r e In ch , u p q . o n

A v er a e elo c i t o f S a e P r es s r e A v er a e el o c i t o f S a e P r es r e g V y f u , g V y f s u , R i S r a c e P o d s R b i S r a c e u bb ng u f , un u b ng u f , P o und s

F eet er M i te er S . I n . F eet er M i t e I er S . p nu p q p nu p q . n

S lo w a n d Inter m i ttent

50 to 1 00

s Colla r Thrust Be a ri ng . In collar thrust bearings , the thrust is taken by proj ections or shoulders o n the shaft,

s o ften at some distance from its end . Thi type of bearing is used when a greater thrust than can be conveniently placed on a single ﬂ at or step bearing is to be taken care \ o f - f . In a well made bearing, ea ch o the collar surfaces takes its proportionate part of the load , and it is thus pos sible , without using excessive diameters , to distribute prop erly a very great thrust on a number o f colla rs formed solidly with the shaft by cutting a number of grooves in the l atter . One advantage of the collar bearing is that the dif ference between the outer and inner diameters of the bear a t ing surface is not very great , and hence the velocities the outer and inner edges do not vary appreciably ; this , again , eliminates unequal wear on the thrust collar surfaces . The safe loa d that may be placed on collar thrust bearings 6 varies between 0 to 1 00 pounds per square inch . Collar thrust bearings are commonly designed with spe i a l c thrust washers let into the bearing proper , these thrust TdRUS T BEARINGS 2 7

washers bearing against the collars on the shaft . The outer dia meters of the collars are usually made not more than

- one and one half times the diameter of the shaft . In the case of small bearings of cheaper design , the bearing sur faces of the thrust bearings are sometimes made integral

r ecom with the bearing itself, but this design is not to be mended , as it is di fﬁcu lt to distribute the load evenly be f tween the dif erent collars . When the main casting is made , say , of cast iron , and bearing washers of brass are

inserted , it is possible to scrape each of these washers until the shaft collars bear properly against each washer , so that

the thrust is uniformly distributed . In some cases , the bearing washers are made in the shape of a horseshoe ﬁt ted over the shaft , so that each washer can be removed

without disturbing the bearing or the shaft .

H dr u l ll u rt d t B a r n s y a ica y S ppo e S e p e i g . The typ e of thrust bearing which is hydraulically supported has very little frictional resistance and is ada pted to heavy pres B sures and high speeds . earings of this type which have been applied to Curtis vertical steam turbines are so de signed tha t oil ( water may also b e used with this type of su fﬁci ent bearing) under pressure to sustain the load , i s forced between the recessed plates at the bottom o f the shaft and then passes out radially in the form of a thin ﬁlm and up through a cylindrical guide bearing located j ust

above the bottom plates , thus ﬂ oati ng the shaft upon the ﬁ oil lm . Th rust Be a ri ng De sig n Ba sed o n Pri nciple of Wedge s d i l F lm hape O i . The investigations of Profess o r Osborne ' R eynolds , following the experiments of Tower on well

ﬁtted s ﬂ o o car j ournals and bra ses ded with oil , showed that r na l the oil , because of its Viscosity and adhesion to the j o u ,

- is , by the j ournal rotation , dragged into a wedge shaped ' space between thej ournal and brass . This action sets up ' film t pressure in the oil which , in turn , suppor s the load , thus separating the bearing su beari ng fl oati ng the load on wedge -shaped oil films which 2 8 T HRUST BEARINGS fo rm automatically and without employing a high pressure fl a t oil pump . There is usually a annular revolving plate with the bearing face immersed in oil and supported on one or mo re shoes whic h a r e mo unted to tilt a s required by run ning conditions . These bearings are made for both hori

- z o nta l and vertical shafts . The low speed bearings may be loaded to 1 000 pounds or more per square inch when using h eavy oil and high - speed bearings with light oils regula rly 500 o carry loads up to p unds per square inch . The friction

low r xi loss in this bearing is very . According to an a pp o mate rule for vertical bearings having six shoes with the inside diameter one - half the outside dia meter and loaded

o to 350 pounds per square inch of shoe area , the mean c efﬁci ent o f friction is times the square root of the revolutions p er minute and varies inversely as the square root of the unit pressure , when using dynamo oil having a 4 temperature of a bout 0 degrees C . The coefficient of fric tion has been found by a large number of tests to vary be tween and

30 BEARING METALS

s as a plastic support for the ha rder grains . Generally peak o ing, the harder the surfaces in contact , the lower the c efﬁci ent of friction , and the higher the pres sure under ” which seizure takes pla ce . Consequently , the harder the A alloy the better . hard , unyielding alloy for successful operation must , however , be in perfect adj ustment , a state of affairs unattainable in the operation of rolling stock .

- For this reason , the l ead lined bearing was introduced , and the practice of lining bearings has now become almost uni versal .

m r s n b tw n rd a nd ft s fo r B r n s Co pa i o e ee Ha S o Alloy ea i g .

While the harder the metals in co ntact the less the friction , there will also be the greater liability of heating, because of the lack of plasticity or ability to mold itself to conform

o r n to the s hape of the j u a l. A hard , unyielding metal will cause the concentration of the load upon a few high spots , and so cause an abnormal pressure per square inch on such areas , and produce rapid abrasion and heating . The bronzes will operate with less heat than softer composi tions , while the softer metals will wear longer than the I n how harder metals . the matter of wear of j ournals , P ever , the soft metals are more destructive . articles of grit and steel seem to become imbedded in the softer metal , ca using it to act upon the harder metal of the j ournal like

- r a lap . High priced compositions a eused that have but lit tle resistance to wear compared with cheaper compos itions , and low- priced alloys are in s ervice that are not cheap at any price . It is generally conceded that soft metal bear o r na l ings cause a marked decreas e in the life of the j u , and yet they have many marked advantages .

r t s P i ncipal Requi reme nts of Bea ri ng Me al . The principal qualities which a good bearing metal should have are good

- r anti f ictional properties , so as to withstand heavy loads

fﬁci n at high speed , without heating , and su e t compressive strength so as not to be squeezed out of place under high pressure, or crack or break when subj ected to sudden

s shocks . In addition to these , many other properties mu t be considered in a choice of bearing metals depending upon BEARI NG METALS 31

the special purpose for Which the material is to be utilized .

Temperature variation is often an important factor , espe fﬁci ent ex a n ci a lly in refrigerating plants , and the coe of p

“

sion should be considered to prevent undue binding, with e s consequent destruction of the b aring , and the po sible

variation in other properties , such as brittleness , ductility ,

etc under various temperature conditions . In addition , many bearings must o perate under conditions where they e are subj ect to chemical action , wheth r that of brine or a ammonia in refrigerating pl nts , or acids , alkalies , etc . ,

in chemical establishments , and in dynamo and motor con

struction and operation , the electrical conductivity must be

considered as well . This statement applies equally to all

bearings incorporated in electrical machinery, where these

must serve as electrical conductors , s uch as the bearings

for the wheels in trolley cars , etc . The chief properties which have been developed to a greater extent than others in machine design are those of i fr ction elimination and resistance to compressive loads .

a Theoretic lly , all metals have the same friction , according

to Thurston , and the value of the soft white alloys for beari ngs lies chi eﬂy in their ready reduction to a smo oth

surface after any l ocal impai r ment of the surface . U nder

these circumstances , the soft alloys flow or squeeze from s the pre sure , forming a larger area for the distribution of

the pressure , thus diminishing its amount per unit of area .

Further , the larger the area over which the pressure is

extended , the less becomes the liability to overheating and ' consequent binding . Thus the frictional properties of a

r a bearing are in inverse ratio to thei compressive resist nce ,

and invariablythe best b earing alloys , from a high speed

o standp int , are unsatisfactory for utilization in heavy ma

chinery . The introduction of an iron or steel grid to form w

’ b a se o f l the the main bearing, and to be ﬁl ed with much s ofter bearing metals than could ordinarily be used , or in

a some c ses even graphite , is a step in the right direction , and presents p ossibilities of great importance in this ﬁeld

of machine development . BEARING M ETALS

t s s n B r n s Me al U ed i ea i g Alloy . L ead ﬂ ows more easily under pressure than any of the common metals , hence it

- has the grea test anti frictional properties . A number of meta ls exceed lead in this property , but their cost or some a other factor render them unav ilable . L ead is the cheapest of the metals , except iron ; the comparative prices of the metals used in bearing alloys , under normal conditions a r o ( previous to the w ) , were a b ut in the following order one : e 4 5 per hundred pounds L ad , $ ; zinc, $ ; antimony , 1 9 3 3 . h $ ; copper, $ and tin , $ 0 or more It can t us be seen tha t the more lead that is used in a given bearing, the soft r e it is , the less friction it possesses , and the cheaper it can

to be furnished . It is , however , o soft to be used alone , as it cannot be retained in the recesses of the bearing even when used simply as a liner and run into a shell of brass .

- a bronze , gun metal , or some other alloy . V rious other o metals have been alloyed with it, such as tin , antim ny ,

i - copper, z nc , iron , and a number of non metallic compounds , f t o f such as sodium , phosphorus , carbon , etc . , and the ef ec the different ingredients is now fairly well understood.

Alloys Co nt a i ni ng Antimo ny. If antimony is a dded to the lead , it increases its hardness and brittleness , and if tin is added as well , it makes a tougher alloy than lead or anti N mony alone . early all of the various babbitt metals on the n market are alloys of lead , tin , a d antimony in various pro portions , with or without other ingredients added . In such babbitts , the wear increases with the antimony and the price , with the tin . The higher antimony babbitts are used in heavy machinery , as they are harder , while those low in

- antimony are used in high speed machinery . The steady increa se in speed at which va rious operating units are main ta i ned is responsible for a wide defici ency in this field in the duty performed by the bearing metal . The chief dif ficu lt y at present , in the operation of the modern turbine , is undoubtedly the maintenance of satisfactory bearing su r faces . S oft babbitts ha ve never suffici ent strength to sus tain the weight and shock of heavy machinery bearings and

u as can be sed only liners . The tendency to increase in BEARING METALS 3 speed as well as in weight or size of machinery is limited simply by the satisfactory opera tion of the bearing metal

itself . l m Al oys of Lea d a nd Anti o ny . L ead and antimony will s alloy in any proportion . With an increa e in antimony , the n alloy becomes harder a d more brittle . It has been deter

mined that , when it is made of 1 3 parts of antimony and 87 parts of lead , the composition will be of homogeneous stru e '

i ture . If there is a greater proportion of antimony , free crystals of antimony will appear , imbedded in the composi

~ 1 tion ; and , if less than 3 per cent , there appear to be grains of the mixture itself imbedded in the lead as the body sub

“ stance . According to a theory generally accepted , an anti frictional alloy should consist of hard grains , to carry the

a load , which are imbedded in a matrix of plastic m terial , to enable it to mold itself to the j ournal without undue heat n i g. S uch a condition would be met in a lead and antimony

a 13 i alloy having bove per cent antimony, but it is not a dv s a 2 ble to use more than 5 per cent antimony, as the composi P o tion would be too brittle . The ennsylvania Railroad C . has adopted the 13 per cent antimony- lead alloy a s a ﬁlli ng metal for bearings , in order to obtain the best results .

The friction becomes less with an increase of antimony , and the temperature of running is likewise diminished when running under norma l conditions ; but the harder the di fﬁcult alloy , the more y is experienced in bringing it pri

marily to a perfect bearing, and the greater the liability of

heating through aggravated conditions . The wear on the a j ournal is not decreased with increasing h rdness , as might o u r na l be expected . This j wear is in all probability not due so much to the alloy directly as it is to the fact that the soft er metals collect grit , principally from the small particles

of steel from the worn j ournal , and , acting as a lap , cause a r rapid wea r . With the harder metals these particles e

o worked out with ut becoming imbedded . The cost of the

r lo I t i n lead and antimony alloy is ve y w . can be used many services where higher -priced alloys are relied upon

mainly for their high cost . It is one of the greatest ex 34 BEARING M ETALS tr a va ga nces of large industrial establishments to use mate rials that are too good for certain uses , and even p erhaps s unsuited , under the suppo ition that they must be good b e ca use they are expensive . This fact has no greater exempli i ﬁca t on than in the purchase of babbitt metal , and is due to the great uncertainty which exists not only among users , but among the manufacturers of these bearing metals .

ntim i . Alloys of Le ad, A o ny , a nd T n It should not be as sume d that antimony—lead is the cheapest alloy to use under

e s e all circumstanc s , becau e , when high pressur s are to be

e encountered , tin is a very d sirable adj unct . Tin imp arts to the lead -antimony alloy rigidity and hardness without

o f u fﬁci ent increasing brittleness , and can produce alloys s e e compressive strength for nearly all us s . The structur of

e a triple alloy of this nature is quite complicat d , and not yet fin suffici ently de ed. The cost of the alloy increases with e su ffi ci ent an increase of tin ; but , for certain us s , where compressive strength cannot be o btained by antimony , b e

s cause of its accompanying brittleness , it is indispen able , and will answer in nearly every case where the tin basis babbitts are used .

s o f Ti n a nd Ant mo n a r e Alloy i y. These alloys e s ldom e e used a lone as bearing metals , but are xtensiv ly used for

“ ” - so called B ritannia ware , and in equal proportions for valve seats , etc .

l s f in nt m n a nd r Al oy o T , A i o y Co ppe . This combination is what is known as genuine babbitt , after its inventor , who presumably was the ﬁr st man to conceive the idea of

o lining bearings with fusible meta l . All ys of this compo

s sitiou are among the most generally used bearing metal .

They form a large group of varying compositions , some of “ B which are given in the following, under abbitt

s of Ti n nt m n d a nd r. L a l Alloy , A i o y , Le a , Co ppe ead ,

e though a soft metal , rend ers this alloy , wh n added in but

o e small pr portions , hard er , stiff r, more easily melted , and superior in every w a y to the alloy without it . This is one of the instances where cheapening of the product is bene ﬁci l a . BEARING M ETALS 35

l The f or egomg represents the more 1mp o rta nt combm a

ti ons of alloys of ti n and lead basis . These alloys are of

’ far more importance in the arts than the white metals , the At o main portion or basis of which is zinc . vari us times

new combinations of zinc have been proposed , but , with

very few exceptions , they have not come into common use s for two reasons : First , becau e of the great tendency of zinc to adhere to iron when even slightly heated . What is techni ca lly kn o wn as galvanizing the j ournal is caused by f thes e conditions ; seco nd , because o the brittleness produced

under the effects of heat, such as is produced by friction

Ta ble I B a bbi tt M et a l C o m o si t i o s . p n

C o m p o s i ti o n o f M e ta l

C la s s o f S e r v i ce A da p ted fo r L ea d

High -p r essu r e bea r ings High p r essu r e a n d fa st sp eed

M edium p ressur e a n d high sp eed . Medium p r essu r e a n d m edium sp eed L o w p r essur e a n d m edium sp eed Pr c a f o r sh a t s etc in ip lly f ing ,

e W hen lubrication is int rfered with , and cons equent danger

of breakage . t t Ba bbi t Me a l . B abbitt is the na me given to a great vari

- ety of white m etal alloys used as linings for bearings . The

name is derived from that of the inventor , Isaac B abbitt , 9 who , i n 183 , obtained a patent for a special type of b ear

- ing enclosing a soft metal alloy . This bearing had lips ex tending around the ends to retain the s oft metal in case of

accidental heating, and also to prevent the soft m etal lining from being spread out when subj ected to heavy p ressure t b tt M t a l Co mpo si io n of Bab i e . The exact composition h of the original babbitt metal is not known . T e ingredients were copper, tin , and antimony , in approximately the fol lowing ﬁr op or ti o ns : per cent of tin ; per cent of

o copper ; per cent of antim ny . This metal possesses

- great anti frictional qualities , but the high percentage of tin makes it expensive and has led to the substitution of 36 BEARING M ETALS other metals which are marketed under the name o f ba bbitt ” e metal . These cheaper grad s , when properly made , are

superior to the o riginal babbitt metal for some purposes . The composition of babbitt metal should be varied accord ing to the pressure to which it will be subj ected and the speed of the rotating member ; the size of the bearing and thickness of the babbitt metal li ning should als o be consi d ered . While it is not necessary to use a different composi tion for each slight variation , a different grade is prefer able when the conditions are radically different . The com positions o f metals fo r different classes of bearings fra quently used are given in Table I .

Ta ble II . B a b bi tt M e t a l C o m p o s i t i o n s

A ti m o y , N u m b er n n P er c ent

bbi - r ss s Ba tt fo r S u b p e Slide . One of the uses for babbitt

- is in sub presses where the plunger slides up and down . A special babbitt is used for this purpose consisting of 66 per

1 8 r 1 6 ; cent of lead , p e cent of antimony , and per cent of tin Americ an S o ciety fo r Te sti ng Ma t e rials S pecific atio ns fo r

B bb tt M t ls - a i e a . A sub committee of the American Soci ety for Testing Material s has proposed to reduce the large

ﬁv number of babbitt metals in use to e, a numbe r which the committee thinks will be ample for every class of work . Table II gives the composition of the seri es which it is be i l eved covers the range for all r equirements . o Where cost is of no great imp rtance , the original babbitt formula is still considered the standard of excellence in the trade , and ha s b een adopted by many of the leading rail nd roads , the United States Government , a many industrial a establishments . It is used in the m j ority of cases where cheaper composition would do equally as well . It is the c most ostly bearing alloy , due to the high content of tin .

38 BEARING METALS

l may be completely borne by the oil ﬁ m but , during the time ﬁlm of starting or stopping, the is broken , minute irregular

ities on the surfaces of the bearing and j ournal engage ,

e and , if the bearing does not yield , as in the case of a ste l

bearing and a steel j ournal , small particles are fused and

o ut a torn ; these accumulate at the entr nce point , and may

u r na l r cut both the bearing and the j o . With a steel j ou na l

- running in a white metal bearing, the bearing surface is f entirely dif erent in its molecular structure , the be aring i n equa lities are not strong enough to resist the minute inequal n ities in the j o u r a l, and so , instead of fusing , they yield and

are smoothed out ; consequently, the bearing surface , instead of being inj ured by contact and momentary high co efﬁci ent

of friction , is smoothed and burnished , thus preparing the way for a uniform wedge oil ﬁlm with a minimum coefficient

o f running friction . L aboratory tests show that a lead -bas e babbitt will give

very good results , but such tests of bearing materials are i d fﬁcu lt . and uncertain , and apt to be misleading Similarly ,

chemical tests cannot be relied upon entirely , since a great

deal is dependent on the actual making of the babbitt . L ab

oratory and chemical tests , taken in conj unction with actual

service tests , furnish reliable data , and a bearing metal de velop ed along these lines may be counted upon to give con

sistent results in practical work . B abbitts made up accord ing to nearly 300 different formulas are at pres ent on the

o beneﬁt market . It w uld be of very great to the users of babbitt if this number were greatly reduced and the process of manufacture sostandardized as to insure a uniform qu al ne ity of alloy . E xcept for a few cases , but two babbitts , o

- - a lead base alloy , the other a tin ba se allo y , each being the

o best that can be made , are required for a c mplete line of

bearings , ranging in weight from a f ew ounces to several

tons .

B r nz B r n M t s o e e a i g e al . B ronze is the term which origi nally was applied to alloys of copper and tin as distinguished o from all ys of copper and zinc . A bronze is usually under

stood to have more copper than tin , and the propert ies of the metal differ widely a ccording to the percentages of these BEARING METALS l constituents which are present . In general , the alloy hard ens when tin is present up to proportions of 30 per cent or a little over , and , when this limit is exceeded , it takes on more and more the nature of tin until pure tin is reached . o ne From a sci enti ﬁc point of View , this alloy is of the most interesting, and has attracted the att ention of many investi gators , who have spent years of study on i t, to learn its various properties and explain its constitution . The a r alloys of interest in this connection , however , e those which are s o constituted as to be adapted for bearing 3 1 5 purposes . These wo uld be said to contain from to per

9 . cent of tin , and from 85 to 7 per cent of copper The alloy of tin containing a small percentage of copper is often used as a babbitt metal , but this comes under the class of white B metals , which have already been discussed . ronze contain ing above 1 5 per cent of tin has been recommended at vari ous times for bearings , owing to its hardness , but such a bearing demands mechanical perfection and perfect lubrica wn tion . It has no plasticity of its o , and , as soon as the oil ﬁlm “ ” is interrupted , rapid abrasion and seizure take place , with hot boxes as the result . The very erroneous idea is still

ha o held by ma ny t t, t resist wear and run with the least pos

sible friction , a bearing alloy must be as hard as poss ibl e. It is true that hard bodies in contact move with less friction than soft ones , but the alloy which is the least liable to heat and ca use trouble is the one which will stand the greatest amount of abuse ; that is , an alloy which has su fﬁci ent plas ti ci ty to adapt itself to the irregularities of service without undue wear . The alloys of copper and tin were used exten si vel - ﬁve y some twenty or twenty years ago , and were con si der ed the standard for railroad and machinery bearings . “ ” The old alloy , known as cannon bronze , containing 7 parts

a nd 1 s eci ﬁe of copper part of tin , is still p d by a few unpr o r ess i ve g railroad men and machinery builders .

B r nz e nt n n r Ti n a nd o Co ai i g Co ppe , , Le ad. This compo

1 1s sit on now the recognized standard bearing bronze , its a d vantage over the bi - compound coming from the introduction of lead . The bronze containing lead is less liable to heat 4 0 BEARING METALS

f d s o . un er the ame state lubrication , etc , and the rate of

i . is wear s much diminished As lead cheaper than tin , it i s desirable to produce a b earing metal with as much lead and b “ E ” as little tin as possi le . The metal known as x . B . com 7 er 1 5 o 78 position (tin , p cent ; lead , per cent ; c pper , per cent ) is stated to be the best that can be devised . This alloy contains the smallest quantity of tin that will hold the lead alloyed with the copper . B y adding a small percentage of 1 nickel , however , to the extent of fro m to per cent , a larger proportion of lead may be us ed , and successful bronzes have been made by this process , which contained as

30 . much as per cent of lead Such bronzes , containing a f large amou nt o lead , through the addition of nickel , are “ ” known in the trade as Plastic bronzes ~ and are a regular commercial article . U fi l ndoubtedly, in investigations in this e d, suffici ent a t tention has not been paid to the eff ect of temperature on the bearing properties of the alloys used for these bearings . More rigid investigation in this field and limitations in r e gard to the temperatures permis sible , with means for main

r e taining these within fairly close limits , will undoubtedly sult in a great increase in the possibility of improvements in f M speed and weight o f vario us types o machinery . ore or less extensive experiments along these lines are being con ducted in regard to the bearings used in turbine constru e e a tion , since the speed here has re nder d the problem an cute one and is necessary for efﬁci ent operation of the turbine itself .

mm r B r t s . Co e c ial ea ing Me al Table III , Composition of ” s B M o Alloys U ed for earing etals , sh ws the various con sti tu ents of the more or less common bearing metals n ow o f bab on the market . A wide deviation in the composition ﬁr st bitt is shown in the ﬁr st part o f the table . The babbitt

- is a fairly good alloy for high speed machinery , but is not F e . very hard . Its melting point is about 500 d grees ; in fact , the pro perties of all alloys or bearing metals can be very widely deduced from their melting point . The second babbitt is somewhat harder and melts at a higher point . Th B oth of these are used largely for lining purposes . e BEARI NG METALS 1

fourth babbitt is used very widely for heavy machinery. s All of the ba bbitts mentioned have been fairly succes ful .

B abbitt 6 has go od wearing properties , but cannot be used Mo o f for high speeds . st the other metals included in the s table , where copper is not used in exces , can be regarded t “ ” as in the same cl as s as babbit s . The white class has a fairly good electrical conductivity , much greater than that of ordinary babbitt, and is used in the bearings of gener a to r s, motors , electric cars , etc . In alloys containing so dium

T a ble III ; C o m p o si t i o n o f A llo ys U s ed fo r B ea r i n g M et a ls

O t h er Allo ys L ea d Z i nc C o n s ti t u en t s

0 0 0 0 0 0 0 0 0

B a bbitt 5 B a bbitt 6 B a bbitt 7 W hite m eta l 1

White m eta l 2 . White b r a ss 1 B r onz e . B r o nze 2 P z B r o nz e 3 B r o nz e 4 B r o nze 5 B r o n z e 6

i r N o t e : P i nd ca t es p h o s p h o u s . the oxidation of the sodium produces a material which will

o saponify with the oil used in the bearing and pr duce soa p , thus as sisting lubrication . Practically no experiments have been made to determine the extent and amount of such o P acti n . ossibilities along this line , however , are great , not only for this particular alloy , but for many others not as yet considered. The h ot er alloys included in the table consist , to a very ' a n l great extent , of copper , tin , and lead , d u su a ly have a r e o f ’ ba bbi thin liner of lead o som s t tt , and hence wear much better than an entire bearing of the soft babbitt . The ten dency to wear decrea s es with increase of lead and increase 4 2 BEARING M ETALS

f a o f tin . Increase of lead , of course , af ects the friction l quantities of the alloy , hence its heating properties . A cer tain amount o f other metal , however , is necessary to keep “ R the lea d from separating from the copper . The P . . R . ” ca r brass , B is considered one of the best bearing bronzes that can be obtained . It contains approximately the small est quantity of tin that will hold the lead alloyed with the “ ” I B a of copper . Ta ble V, Composition of ronzes , gives list

N . alloys used by the U . S . avy Department

z Ta ble IV . C o m p o si ti o n o f B r o n es

Zi c A llo ys L ea d n

W hite m eta l Ha r d b r o nze fo r p i s to n r ings ' B ea r ings w e a 1 t s r a ces e c . . ing u f , Na va l br a ss

B r a zing m eta l .

u bst t ut es fo r Ti n i n B r n Met a s S i . ea i g l . The B ureau of

Standards , in its efforts to determine to what extent substi tutes may be us ed for tin , calls attentio n to the limited sup d ply and great demand for this metal , a n mentions that it is imperative that steps be taken at once to eliminate all waste o f tin and to use s ubstitutes or reduce its use as far as p os sible and practicable in all alloys . It is pointed out that many speci ﬁcati ons for bearing meta ls no w in existence call for pure tin , and that a large saving of high grades of tin , as B such anca or Straits , could be brought about by allow ing the use o f second quality pig tin in making tin -base babbitt . Detrimental impurities could still be limited . but a maximum of 1 per cent of lead could be allowed . This would

- - not be harmful to a tin bas e or lead b a se lining metal . There is no question but that the tin content could be reduced somewhat in all bearing alloys . E very possible saving

f i should be ef ected . For thos e cases where genu ne babbitt

is now used and which require a very high grade of lining,

a r e alloys suggested containing either of the combinations , 0 BEARING METALS 4 3

5 85 per cent tin , 10 per cent antimony , and per cent copper ; 6 2 8 or 65 per cent tin , from 3 to per cent copper , and from to 30 per cent zinc .

‘ L ead -base linings can be satisfactorily used in many cases

- a where tin base linings are n ow in use , and in fact the ch nge substi tu has already been made in some shops , although the tion sho uld be more general . S everal special types of lead base linings , hardened with a lkali earth , are reported to be giving very satisfactory service in the place of high tin bab bitt . Two other alloys containing large percentages of lead and zinc have apparently been found to perform the sa me serv ices which were required of tin -bas e linings in machine 8 tool work . One of these alloys consists of 8 per cent tin , 4 80 per cent antimony, per cent copper , and per cent lead ; ni and the other co sts of 5 per cent tin , 7 per cent antimony , 2 6 per cent copper , 1 0 per cent lead , and 7 per cent zinc . One wa y in which a lining metal can be s aved is to use as thin a lining as is p o ssible in order to maintain a high enough temperature during pouring to guarantee a ﬁrm o bond and s lid mass of metal . In place of a bronze bearing 1 containing 80 per cent copper , 0 per cent tin , and 1 0 per cent lead , an addition of a small percentage of zinc or phos phor - copper and an increase of the lead content will result 2 5 in a saving of at least per cent of the tin ingredient .

m r s n of d-b s a nd Ti n- s B t Co pa i o Lea a e ba e abbitt Me a ls . ' i n Tenacity is desirable a bearing metal , especially at the higher bearing temperatures , as bearings fail because of warping o r deformation . The following information on the relative merits of lead -base and tin -bas e babbitt metals was abstracted from a paper presented before the American In i L st tu M E . te of ining ngineers by J J ones , metallurgist, E Mf o Westinghouse lectric g . C . The B rinell test is co mmonly regarded as a meas ure of tenacity ; i n fact , the proposition has been made to substi tute for the term “ B rinell hardness number ” the expression “ ” B tenacity number . rinell tests at progressively increasing tempera tures showed that the lead - bas e babbitt has a better resistance to deformation a t the working temperatures than

s babbitts with a tin ba e . The tests were made on disks 4 4 4 BEARING M ETALS inches in diameter and inches thick of the following composition

ti o r y, g o p l l e T n ' ’ i ) l men I ex z ht B a bb tt ?E t ?) P eg éght P er EJ en t 2 0 9 0 8 1/3 0 83 0 7 8 8

hot The disks were heated by an electric plate, the tem er a tur e p being controlled by suitable rheostats . Pyro meter t leads were soldered in the cen er of each disk . The disks were well insulated to prevent radiation l oss and were held at the desired temperature for s everal minutes to guard against variation . The tests were made on the bottom sur face of the disks after a light machine cut was taken to s ecure a perfectly planed surface . The B rinell hardness numbers obtained at the vari ous temperatures were plotted a nd s the re ults are shown by the curves given in Fig . 1 . At 35 d nti degrees C . the hardness of the babbitts A and C is i e

- cal , but above this temperature the lead base babbitt has the B higher hardness number . The curves of babbitts and C r e are almost pa rallel and not very far apart . Complete ult ﬂ o or s s s from various test , covering a number of gears onﬁr m and a variety of motors , c the superiority of the lead wa s base babbitt . In one case where it necessary to reline

‘ n ni n t one hundred bearings co ta i g b abbi t A in a month , it was necessary to reline only about six bearings that con ta i ne - - d the lead ba se babbitt C . As a result , the lead base wa s e babbitt substituted for all classes of machines and . th — tin base babbitt A eliminated altogether . While the B rinell hardness shown in the chart for the ba bbitts A and C is not far from the average hardness found e fo r these alloys when using the standard hardness test piec , the results obtained for the hard babbitt B is much below di fﬁcult the norma l . This probably is due to the y of pre b venting the large amount of copper in this babbitt f r om segregating even when kept very hot and being stirred con ti nuo u sl y. The copper falls to the bottom of the melting pot ; hence when stirring, the a i m should be to bring the metal from the bottom of the pot to the top .

4 6 BEARING METALS

and hardening it the bearing will give better service . In one case where two phosphor- bronze plates were co ated with e babbitts B and C , then subj ected to pr ssures varying from u 8500 to pounds per sq are inch , it wa s found that the

- - lead bas e babbitt stood up better than the tin base babbitt . When the load wa s increased to pounds per square

Fi . 2 ct f L d n H r d e f B tt g . Effe o ea o a n s s o a a bb i

c - in h , the tin base babbitt presented a better appearance , as it ﬂowed uniformly over the edge of the bronze square in all

- directions , while the lead base babbitt was compressed more o ne h on side than on t e other . The tests show that broach ing, peening , etc . , do not appreciably increase the hardness of babbitt ; hardness must be obtained through quickly cool

- ing the babbitt lining by means of water cooled mandrels ,

- etc . A micro scopic examination of a lead base babbitt BEARI NG METALS 4 7

shows tha t the metals tend to segregate . This lack of uni formity may be guarded agains t by p ouring a thin lining and chilling quickly . The secret of obtaining good bearings consists in keeping the matrix tough and hard . There is less tendency for tin antimonide crystals in tin -base babbitts to rise to the surface , becaus e of the lower gravity of these babbitts .

s - Mi cella neo us Be a ri ng Met als . A high class b earing metal is prepared as follows : Melt 7 parts of copper at as low a heat as p o ssible ; then add 2 5 parts of antimony and 2 00 . parts of tin . This mixture is cast in iron ingot molds

It is then remelted and to . each five pounds of the ingots is o as added eight pounds of tin , this sec nd alloy being c t in bars to suit the requirements . For an anti -friction metal that can be subj ected to pres 4 sures up to about 00 pounds per square inch , the following o compositi n ha s been recommended : L ead , 85 per cent ; Fo r antimony , 10 per cent ; and tin , 5 per cent . pressures 4 exceeding 00 pounds per s quare inch , the following alloy will prove satisfactory : Tin , 85 per cent ; copper , 5 per 1 cent ; and antimony , 0 per cent . This alloy can be used safely for pressures up to 1000 pounds per square inch . The alloys in Table V a r e stated to have given complete satis faction for the purpos es mentioned . An alloy made by melting together approximately equal parts of cadmium and zinc , with an addition of a small pro portion of a ntimony is s aid to be superior to the usual white metal . It is very easily worked and particularly easily l turned , it fil s up the mold completely when cast , possesses o s relatively great hardness , and , what is m t important , it m co effici nt has an extremely s all e of friction . The alloy can consist of from 4 5 to 50 parts of cadmium ; from 4 5 to 50

10 o parts of zinc ; and up to parts of antim ny . The anti 1 0 mony added should not exceed per cent , as otherwise the A metal is to o brittle . very suitable proportion of antimony a nd is 5 per cent . If the proportion of cadmium zinc is con co efﬁci en s si der a bly varied , the t of friction increase , and the other good properties of the alloy are essentially p r ej u diced . 4 8 BEARING METALS

s r n M t s . R K L B lond M Test o n Bea i g e al The . . e achine has Tool Co . , Cincinnati , Ohio , made a comparative test of bearings fo r la the spindles on two of the engine lathes in its plant , to determine the relative durability of the following

o V z : - combinati ns , i . hardened steel j ournal in cast iron box ; hardened steel j ournal i n bronze ; soft steel j ournal in bronze ; and soft ste el j ournal in babbitt . The experiment was ma de on both ends of the spindles , thus making the four s combinations named . Bo th lathes were kept in con tant use , the general character of work being the same for both .

When examined , the condition of the hardened steel j ournal

- ll and cas t iron box was the best of a , neither the spindle nor

Ta ble V M i sc ell a eo u s B ea r i M et a ls . n ng

A ti C o p 8 1s U s ed fo r L ea d Z 1 n c n m o ny p er m u t h — Dyn a m o s high - sp eed M a r in e engin es E ccen tr ics Subm er ged bea r ing s a ea r M in b ing s . es t r st ea r s Slid , h u b ing R a ilwa y tr u cks Axl e-bo xes 1 3 50 Pl a sti c m eta l G enuin e ba bbitt ( h a r d ) e e a tt No 2 G nuin b bbi ( . ) U niv er sa l bea r ing m eta l 77 75

bo x the being appreciably worn , the grinder and scraper

e markings still being Visible . The harden d steel j ournal and bronze box combination wa s in good shape , but the j ournal wa s slightly ridged in the center , showing more wear than ﬁr the st . The soft spindl e in bronze was worn appreciably,

- but the soft s pindle in babbitt w as in fi rst class co ndition . The fr ont bearings were provided with oil rings and oil

reservoirs , and the main bearings with oil reservoirs and

felt wicks . Investigations to ascertain to wha t extent repeated melt ings of bearing metals i nﬂu ence their strength and reliability showed the following results : As regards white meta l r e ( alloys of copper , antimony , and tin ) it wa s found that ’ qEARI NG METALS 4 9

p eated meltings did not noticea bly alter the grain , but that ' nﬂ o the rate of cooling had a cons iderable i u ence. Quick co l

ing yielded a ﬁner grain and a higher hardness and strength , and it is recommended that white metals should no t be heat ed 'to high tempera tures and that they should be cooled rap B idly . ronze , poor in tin , and , therefore , comparatively e inexpens ive , may have the hardn ss and strength increased by being rapidly cooled from a temperature of 14 4 0 de F grees . While a great deal of attention has been given to the

a i investig tion of the propert es of bearing metals , there is o still a great deal to be d ne , and many impo rtant points are t n yet to be de ermi ed . Apparently many bearing metals are unnecessarily expensive , containing higher p ercentages of

- high priced metals than i s r equired . CHAPTE R III

METHO DS OF L UBRICATING BEARINGS

AsIDE s from the election of the lubricating oil , the proper lubrication of bearings requires a careful study of the best means o f conducting the oil to the bearing surfaces and also means of protecting the bearing against the entrance m of foreign aterial such as would inj ure the surface . Far more attention is n ow paid to these details than wa s the s c a se formerly , e pecially in metal working machinery . The s e higher peeds and duti s which prevail , the use of geared

o - i n drives , and the practice of b xing portions of mechanism , n have all had their effect upon the methods of lubricatio , a new e e and m ny and improved . devic s have be n developed and come into general use . The tendency is always to ren

ca o as t der the lubri ti n , far as p o ssible , a u omatic in the most complete systems; so as to obviate frequent attention on the part of the attendant , and to minimize the consequences of Th f a neglect . e details o constructio n of m chine tools are so complex and varied that it is not surp rising to ﬁnd a multi tude o f wa ys o f supplying oil to thedifferent elements , and the principal of these will be described in detail , with the help of typical illustrations . The question of lubrication divides itself naturally into two main heads , viz . , supply and s distribution . S ubsidia ry to these are , the prevention of lo s before the oil ha s done its work , the prevention of access of

ﬁna l dirt to the surfaces , and the catching of the lubricant e r e after it has left the surfaces , with or without immediat e turn . In many insta nces , it is necess ary to prevent escap of o il to belts a nd surfaces where its presence i s undesirable .

Oil u . f S pply The oil supply is ef ected by gravity , by pres on sure , by capillary attraction , by a mechanical lifting acti c a th whi h r ises oil from a well , or by contact, through e

50 LUBRICATING BEARINGS 51

o n i s ef medium o f wicks , pads , or r llers . The distributio fected by rows of holes , or grooves , by wicks or pads laid

. S suitably , by rollers , or by the splash method uch varied conditions are met with that it is impossible to claim any particular mode o f lubrication a s being the best for shafts f or slides . The speed of rotation may make a vital dif er ence in the results , and a method of oiling that is quite sat i sfa cto ry in one machine may be undesirable or i mp r a c ti ca ble in another , on account of inaccessibility of the parts or great increase of pressures . With the use of the boxed in geared drives in so many types o f metal wo rking ma i t chines , the d fﬁculti es of reaching the p ar s have increased , and some rather elaborate devices have been evolved for supplying and catching the oil witho ut having recourse to P o the removal of covers . ipes naturally play an imp rtant s hart in the conduction , a nd there is often exten ive drilling of shafts and bearings for the purpose of conveyance from the outside . ua nt t of il Q i y O . One of the greatest differences which a ffect the lubricating problem is the quantity of oil which has to be supplied , and this depends on the function of the t s moving par If it runs at a good speed , under con ider c able duty, a opious supply is essential to p revent cutting

and heating, but if the movement is slow or intermittent l and the work light , a s imp er system meets the ca se . In

sliding ways , which run at high speeds a nd carry much

weight , ample lubrication is imperative , while, on the other

- - hand , such parts as cross slides , tool boxes , etc . , which move slowly or intermittently will retain their ﬁlm of oil

o new for a l ng period without a supply . The horizontal or vertical dispositions of sliding surfaces also make some dif

e o i l fer nce in the amount of which can be fed . Certain ﬂ oodi n horizontal ways admit of g without inconvenience , s o while thi cannot be d ne with a vertical slide , nor would s E it usually be nece sary . ven when ample lubricant is fed s to a bearing or lide , this is of little avail unless distributed

correctly and evenly , so that no parts of the surfaces be

come dry . 52 LUBRICATING BEARINGS

It is not suffici ent to drill a hole and trust that the oil will get between two surfaces beyond the vicinity of the hole , although this is often done in cheap work . The oil must be distributed to the right and left in a definite man ner , with due allowance for possible clogging . The two chief methods of effecting the spreading are grooves or channels , and pads of felt . The first named is satisfactory provided the quantity fed in is suffi ci ent to carry it the r e quired distance ; the latter has the merit of absorbing a good deal of oil and keeping the surfaces moist for a cer tain period , even if negle cted , and it also prevents the

ﬁtted . access of grit if properly , which grooves alone do not c o Sometimes a ompromise is made , using gr oves and pads together . If the pads are let into a well of oil , a certainty of supply is guaranteed , although this will not distribute such an amount of oil as some other methods . The arrangements for catching and draining the oil from a surface or bearing i nﬂ u ence the mode of feeding to a certain extent , and the two must be intimately related . A copious quantity of oil does not do much good if it is per mi tted to run out quickly and has to be collected in a primi tive fashion , with inevitable waste . Under the pump and

ﬂ o o ded bearing system , thi s is practicable , but , for ordi a a s v n ry use , a moderate mount upplied at—inter als is bet ter . When , however , ea ch bearing is self contained , with a

- ring oiling or similar system , the amount of oil passing

o constantly is not restricted , but depends up n the method of lifting adopted . There is no waste here , because the oil from the surfa ces returns to the reservoir and is carri ed e again to the points at which it is ne ded .

il st r t O Di ib u io n. In the means provided for distributing and catching the oil , widely varied methods are adopted , ranging from simple pots or troughs under open - ended

- bearings , to the highly elaborated systems in which a forced supp ly is fed to the bearings , and is completely collected from these and returned to the pump for use over again .

The latter system , if properly embodied in the design of a machine , is the best solution of the lubricating problem ,

54 LUBRICATING BEARINGS

o ca tor s often take the pla ce of th se with soiled metal bodies, in places where they are permissible . Occasionally a ﬂ oa t gage is utilized to indicate the level of the oil . With a gear box of ample capacity, no indicator may be necessary , since

n u i n a certain amount is poured i , s fﬁc e t to last for so many

- weeks or months ; and , in the ca se of some ball bearings , a grease supply sufﬁ ci ent for a year or so is put in and the casing clos ed u p . The access of dirt and grit is guarded against by using ﬁ a strainers and lter s . In a well sytem of lubric tion the sediment naturally falls to the b ottom , and care should be taken that it is not stirred up again ; in fact , many bearings emb ody provision for keeping the sediment in such a wa y

D - w that it cannot possibly be returned . rain plugs at the lo

- est position provide for the drawing off at intervals . When using felt p ads , there is opportunity to make these assist in keeping the surfaces clean by a wiper- like action which prevents access of foreign particles between the rotating or sliding faces . The amount of protection which must be afforded to bearings and parts depends upon the nature of the processes carried o n in the shop . Anything in the way o f grinding demands rigorous guarding of all openings a re ed where a ccess is possible , and felt pads and disks us largely for such purposes .

r he Example s o f L u b ic ati ng Devices. T most primitive mode of oiling is that of drilling a hole and pouring oil into

An a d wa . it, leaving it to work its y along the bearing vance on this is to groove the bearing so that distribution takes place properly , and supply some means of insuring ﬂ a constant ow of oil . A simple arrangement consists of a wick leading from the bearing to a small reservoir of oil . Such a bearing is very suitable for light and moderate duties , and will run for a long period without attention , although it is not so suitable for high - S p eed shafts which require ﬂushi ng and continual movement o f the oil to make i s them run coo l . On many bushings and bearings the oil not distributed by a single hole and groove in the j ournal , but instead there is a long slot and several holes lead from LUBRICATING BEARINGS 55

s it to the bearing surface . This is convenient , in some case , especia lly where bearings are di fﬁcult of access , and where they have a longitudinal movement which would bring a

. Two single feeding o pening out of the range of a pipe . holes are often drilled through near each end of a long o bearing, so as to insure a distribution fr m both ends . Thrust j ournals constructed with a number of colla rs

a . may be lubricated on the separ te passage system , Fig 1 , l a hole for each col ar leading from the common reservoir . This example is taken from a heavy planing machine table

F I . 1 T r st B e r w t O i l S t r g . h u a ing i h u pp ly o E a c h C o l l a driving s crew ; the illustration also shows the application of a trough below the end of the bearing to catch waste , a ﬁtti ng that is very commonly used in various types of screws and other bearings that come at the ends of fram ings . Alternative practice 1s to cast a well below the col

u i n . lars of s fﬁc e t wi dth to include them all , and ﬁll this os The collars then are constantly smeared , avoiding the p si bi lit or m or e y of one , running dry due to the hole being w s b blocked ith some foreign u stance , as ma y happen with the arrang ement sh own in Fi g. 1 .

u br c t n b F t ds L i a io y el Pa . E xamples of various methods of applyi ng felt pads for distribution are found in different machine tool designs , the felt pads being used either alone, or in combination with grooves in the bushing or on the 56 LUBRICATING BEARINGS

not shaft . The felt only insures a supply of oil on every ﬁlter s part o f the j ournal that it touches , but it the oil as

o r . well , and prevents the passing of grit particles of metal

The p ads are ﬁtted into slots cut in boxes or bushings , and either dip into a well , or are simply fed through holes by a

2 n . D A c a t o s o f P a d a nd Reser o r F i gs . a d 3 i fferent p p l i i n v i S y st ems

Fi m S d . P ro e g 4 . a d a nd R es erv o i r S y st em w i t h S u p p ly f i

cam , or from some type of lubricator . The pad is often let into a capacious well holding sufﬁci ent oil to last for a long 2 s period ( Fig . ) with provision for the return of the wa te oil by a channel from the end or ends of the bearings . Figs . 3 4 r s and show two variations in practice, the ﬁ t having a side fed well , and a pad contained in a brass holder pressed LUBRi CATI NG BEARINGS 57

modi ﬁed by a spring , and the second a arrangement , with the oiler set vertically . This disposition is sometimes more convenient for certain machines than placing it on top of thebearing ca p , and there is the advantage that grit can not reach the spindle , as it may when the supply is poured ﬁtti n down from above . Alternatively to the g of a pad , wicking is sometimes adopted .

In Fig . 5 there is shown a form of construction which has been adopted for beari ngs used to support horizontal a and vertical driving sh fts on certain machine tools . Oil

F i t d f L r g 5 . M e h o o u b i ca t ing Ho r i z o nt a l a nd V ert i ca l M a c h ine T o o l D r iving S h a ft s is delivered through a tube which carries it into an annular

of space machined in the outside the bronze bearing box , and the oil flows around through this space to the opposite side of the box from the point at which the delivery tube is connected . Here there is a slot cut through the box to a communic te with the inside or bearing surface , this slot fl ow being filled with felt . The oil s through the felt to the ri i n bearing, a d the felt serves the double purpose of filter g impurities from the oil and acting as a wiper which dis tributes the oil evenly over t he surface of the bearing which it is required to lubricate . The illustration clearly shows the arrangement of this simple method of lubricating . 5 8 LUBRICATING BEARINGS

f or Ring Oiling . A system most extensively employed

- spindles and shafts is the ring oiling method , which insures a larger ﬂ o w than is caused by the pad device . This method of providing for automatically delivering o i l to a beari ng requires one or mo re rings which are hung over the top of each j o u r na l and extend down sufﬁ ci ently below the j ournal at the under side so that they dip into a reservoir filled with ' oil . As the j ournal rotates , it carries the rings around , thus bringing the portion of each ring which was formerly immersed in the 011 up into contact with the top of the

e o j ou r na l . The ring carri s a considerable am unt of oil

Hei t a e F i . T w o R n s a nd g 6 . B ea r ing w i t h O i l ing i g gh G g ( A ) P e rf o r a t ed R ing

i t with , and in this way a constant supply of oil is deposited on the j ournal . This method is used in conj unction with a reservoir for each bearing , or with a reservoir or box common to several

- bearings . If a gear box , for example , has a body of oil into which the gears run , pas sages can be arranged to lead to the bearing wells , which simplifies arrangements ; or the bearings may be constructed in a self—contained manner if they lie out of the plane of the oil box . In long j ournals it is often the practice to employ two oiling rings to provide greater quantity a nd better distribution of the lubricant . An i instance of this is seen in F g. 6 , which also illustrates

- the gage glass fitted to observe the height of oil . Sediment . m. 3 w $ 5 n 3 o 8 9 o : 5 n vo 3 ” 3 m n 3 . 3 4 Q “ 2 . 5 3 w mv. 5 fl n 3 mB a u : u 5 w 5 x 8 m 5 m fi w a 5 v m 1 2 m 5 a 8 o 9 2 m 3 m 3 s A z s o o 3 m m ? m p 9 3 m 0 o 3 9 o z 3 O z w 3 d w 5 a m 8 n 3 3 E w m m m 3 a m 5 m v 5 o m 2 h m 5 v 2 2 a 3 m E 2 3 3 A 2 m 8 m m m 8 5 ? 0 o 5 o o M 8 m c m 9 : 3 m g 3 x 9 9 9 a 2 5 o » “ 5 8

9 E 5 5 a 3 £ 3 a 3 0 5 5 3 5 a 3 3 5 m 8 9 3 E 3 3 o : m a £ 3 5 5 c . 5 m 9 : o E B 8 o 8 5 3 8 5 S 3 9 a o B 2 3 m n o “ s “. a 3 w 8 s a m a m m o 2 a m n 3 fi 3 s o s w 9 m a : 3 m o fi 3 5 m 3 b 3 z m 2 n 5 m “ 8 8 x 3 ¢ 6 o w 9 9 2 w s 5 2 fi E o 8 5 5 m p3 fi 9 m : : 3 3 o 3 a “ 3 : 8 m 8 o fi 3 2 3 3 fi 3 m 3 3 m fi 0 8 m 3 s z $ m g v x m o m s 8 3 w “. 5 m m a 5 3 z E n o m m 8 5 u o 5 e o a

59 0 LUBRICATING BEARINGS is an important feature on the bearings of any grinding

- machine , and , in addition to the ring oiled radial bearings , thrust bearings are provided to support the load which is applied in a n endwise direction . This combination radial and double end thrust bearing is automatically oiled . It is claimed that this ring- oiling device is so effici ent in m operation that the spindle literally fl o ats on an oil fil , thus greatly reducing the amount of power required to drive the ma chine . Tests which have been conducted to determine the transmission effici ency of these ring- oiling bearings are said to have shown that it is within 2 per cent

fﬁci enc of the e y of ball bearings . In the operation of ring oiled bearings of this type , the oil should be drawn off about every six months , the exact length of time depending upon the conditions of service under which the bearings are op er at d e . The oil wells have ample capacity ; for instance , 1 R No . 7 o on the sly disk grinder , with a spindle inches in diameter , the oil wells are 7 inches deep . Two s o lid steel rings are provided for each bearing, which operate through channels cut in the bearing bushings in such a wa y that it is impossible for a ring to be displaced and fail to operate properly . The bearing boxes are split to facilitate assembly , and the housings in which these boxes are i n serted a r e so arranged that repla cement of the boxes is an easy matter when this becomes necessary . A special grade

- a r of phosphor bronze is used for the boxes , and they e de signed with ample bearing surface so that there is very little wear .

Ou disk grinding machines , considerable end thrust is set up when work is forced aga inst the grinding wheel , and this is particularly true in the case of machines furnished

- On with a lever feeding mechanism for the work table . single -spindle B esly disk grinding machines a grinding wheel is mounted at both ends of the spindle , which makes it necessary to design the bearings in such a wa y that pro vision is made for supporting the thrust load which is a p o plied in both directions . It is als important to work out the design in such a wa y that there will be no end motion

62 LUBRICATING BEARINGS eter that a ll portions of the face of each hardened thrust collar which bears against the ﬂ a nge on the radial bear ing pass over the oil - groove during o n e r evolution of the

e spindle, which insures oil r aching all parts of the thrust

e e d bearing . Oil is also d liv re to this groove from the oil H grooves formed by the bushing liners , to which refer

- ence has already been made . As the oil gr ooves in the t hrust bearings are circular in form , an eccentric with the spindl e rotary motion of the thrust collars against the oil in the groo ves tends to circulate this oil and provide a

ﬂ ow copious of lubricant . After this type of disk grinder

F i 8 S o w L r c a t o n C a n d S r g . . h ing u b i i by h in a by p ing

S pindle bearing was adopted , it was found practicable to increase the speed 75 per cent where such an increase was

desirable .

A bearing on a grinding machine , provided with a chain

e A oiling device , is shown in Fig 8 . The vi w shown at represents a compr omise between the chain and the solid — ring a spiral spring looped and hooked together to revolve

the with shaft .

- r Ri ngs fo r Ring oili ng B ea i ngs . The great variety of rings that a r e in successful use would appear to indicate that the s ection of the ring that is adopted , has little to

fﬁ i n e do with its e c e cy. It can b e se n that a ring of rela ti vely heavy section will be less likely to b e stopp ed by the oil than one of small section and correspondingly light LUBﬁI CATI NG BEARINGS

weight . Rings and oil that do acceptable work after being started often fail to start satisfactorily because the oil is stiff enough to overcome the very slight friction that exists

between the shaft and the ring . This point should be con si der ed in connection with the size of the oil reservoir and

e the kind of oil that giv s most satisfactory results . If the reservoir is made la rge enough to provide sufﬁci ent oil storage to reduce the necessity of frequently renewing the h s i t oil , and the ring ang deep in , there will be a tendency i ﬁll to retard the ring when the reservoir s ed to its capacity .

L arge rings have a smaller area in contact with the shaft , and have a tendency to assume a position oblique to the shaft and to swing latera lly ; cons equently the diameter of

the rings should not be too large . Chain oiling seems to offer many advantages over ring

he o iling, but the cheapness of rings and t fact that they give satisfactory service in millions of bearings , appears to be su fﬁci ent commendation to insure keeping them in use . Some large producers of ring oiling bearings make all their rings below 5 inches i n diameter out of seamless l brass tubing . The o n y obj ection to this material is that a tube is occasiona lly found that is eccentric enough to pre vent satisfactory action . If the ring is very slightly out of

e balance , it will not mov properly and fails to carry oil to

a the bearing in a satisf ctory manner .

r s s - Fixed Oili ng Ri ngs o Di k . With the ring oiling method previously referred to , the ring is hung loosely on the

a . ﬁxe spindle , and revolves at slow rate If it is d to run at

u fﬁ n l f the same speed , the action is not s ci e t y ef ective , be cause the centrifugal force throws the oil outward and very little of it can reach the shaft . When some manner ff of catching or scraping the oil o the ring is included , this

e arrangement is not obj ctionable . For instance , with one

m xed arrange ent , the ﬁ ring or elevator disk thro ws the oil h up into the distributor at t e top , whence it ﬂ o w s along slop ing surfaces which communicate by vertical holes with the

- ﬁlt r top of the bearing . S ome high speed spindles have a e ing arrangement incorporated ; the oil is thrown by the 4 LUBRICATING BEARINGS

disks into a trough at the top , and it runs along this into recesses ﬁlled with ﬁlter i ng material through which no for r ovi d ei gn particles can pass into the bearings . Instead of p

- ing a gage gl a ss for inspection , the simpler plan of screw ing a brass window plate with a small piece of glass i n

- r e r e ser ted is adopted . The oil ring scraping method is p sented by Fig . 9 , the ring being keyed to the shaft ; at the two i top are lugs or scrapers , A , with o nly sufﬁc ent space between them for the ring to revolve . The result is that the oil raised is scraped o ff the ring and thrown into the grooves in the bearing .

i 9 R nd S c r a er et d o f L br ca t o w c Is F g. . ing a p M h o u i i n h i h s o m et i m es e m p l o y ed w i t h S a t i sf a ct o ry R es u l t s

Oil C o ndu cted by Wic ks . Wicking is now largely utilized to supply bearings in a manner that c o uld not be a ccom«

h . pli s ed by pads , or at least not so well The principle is to

e a nd trail the piec of wick in the oil reservoir , lead it from there to the bearing surface ; this is a very elastic principle, and possesses two main advantages . One is that the oil is

ﬁ r lte ed and , consequently , no dirt is transmitted by the wick ; the other , that a feed can be procured from a well or

- gear box not necessarily situated close to the bearing . If the wick is in proper condition , and the oil supply is maintained ,

No there is no risk of the bearings running dry . direct stream of oil ever reaches the bearings , since the wicking is arranged in such a fashion that the oil only climbs by capillary attraction . Fig . 10 represents the application of LUBRﬁCATI NG BEARINGS 65

A long wicking to feed two bearings . subsidiary advantage of wicking is that it can be employed to convey oil thr ough a hole in the side of a reservoir or cup divided by a parti tion into two chambers . One of these is never opened to the air , and cannot receive ﬂying grit or dust from the shop , but only forms a passage to lead the Wick to the bearing

o surfaces . The other chamber c ntains the wicking coiled

10. R er o r nd L o c k s er T w o B ea r s F i g . es v i a ng W i v ing ing

— m s de o f t d w c c a n i 1 1 . L br ca t o r o I S a t a e o F g. u i i n f n i h f M h h i h b e u s ed t o A dv a nt a ge in M a ny Inst a nces

up in a mass to absorb oil , and the communication between the chambers is such that no direct ﬂ o w can o ccur to wash undesirable substances along . S pecial Qil Du cts f There are numerous instances in which the difficulty of reaching concealed bearings results in r the adoption of special p ipings o pa ssages . The advent of all -geared drives for speeds and feeds greatly complicated

. the matter . A common method is to drill a longitudinal hole h d in the s aft , and connect ra ial hol es with this to lead out 66 LUBRICATING BEARINGS

U to the various bearings or wheels . sually the lubricant is supplied through the shaft end , but it may have to be fed

from a radial or inclined hole in some cases . Fig . 1 1 is selected to illustrate both ways , the pini o n and clutch A a nd B receiving oil through the shaft from the end oiler , and the gear C its supply from the inclined passage fed from the piped bearing adj acent . The reason for turning the semicircular groove in the shaft at the place where B is situated is that , as the latter does not revolve , there would be no opportunity for the oil to spread itself circum 12 fer enti a lly. Fig . shows a method of supply to a ﬁxed t pin on which is a pinion and a dis ance piece . A groove is

F 12 a nd 13 . ec t f i l i gs . S p i a l M e h o ds o S u p p lying O

turned in the pin where it rests in the bearing bracket , and a transverse hole lea ds the oil fromthis to the central pas sage . In places where it is not feasible to lead a pipe in from above , as shown , on account of the proximity of gears

ca n or other details , a lateral pipe be inserted ( see detail 12 ﬁll view , Fig . ) to the vertical hole up which the oil rises to the pin . This pipe is either disposed horizontally, or

‘ slopes down , or , if a head is available from a well or tank

‘ o r pump supply , it can be brought up from below . In a few instances it is impracticable to conduct oil through the i center of a spindle , on account of th s being used for the

- pa ssage of a draw rod or a chuck tube . In such a case , a

- 1 3 special oil hole is drilled , Fig . , in the metal between the o central h le and the outside .

P n f r nd ct n b r a nts ipi g o Co u i g L u ic . The combination of holes and pipes is frequently necessary ; sometimes the oil LUBRICATING BEARINGS 67 passes for a certain distance through a hole and then ﬁni shes its j ourney by way of a pipe for precision of location . The ease with which pipes can be bent and carried around angles greatly assists in their disposition , and often saves

P a awkward or expensive drilling . iping is l rgely utilized to span gaps where the lubricant could not be supplied with

he - certainty , and without waste , to t interior oil hole . The close proximity of a pulley or other detail often ren ders it impracticable to reach a bea ring with an ordinary

- oil can spout , so the plan of arranging a pipe is followed , ' the top being closed with a plug , or an oiler . When a num ber of such pipes have to be used , it is usually best , if cir n cumsta ces allow , to bring the terminations all together at one spot , not necessarily into a tank , but alongside into a holding block , and thus have them handy for attention . The practice of covering- i n sets of gears with casings which are necessa ry for protective purposes , or may form an integral part of the design of bearings and lever anchor ages , frequently renders some amount of piping necessary , to lead from the external oilers to the various bearings . The a lternative is to drill the shafts and convey the oil by w o a y of these , but it is sometimes inconvenient to do s .

Th - e oil pipe either leads from the cover to the bearing, or hangs some little way o ff and lets the oil drop into a cupped

hole , or a raised rim , as the case may b e. S ometimes a ﬂ n bushing is screwed into the bearings and has a a ged head ,

- with an ample bell mouth , to catch the oil . The cover can be removed and replaced without disturbing any connec tions , which is not the case when the pipes actually enter ﬁ the bearings and t into them .

- im In a great many feed gears and other details , it is possible to apply oil directly to certain of the bearings , be

cause of their inaccessibility , and , in such cases , it is often the practice to provide a single trough on the top of a ﬁxed or a tumbler casting , and drill holes a nd ﬁt and bend

pipes suitably to reach the other bearings . In order to

s prevent wa te of oil , the trough is sometimes divided by

- partitions , thus providing each leading out hole with its own 68 LUBRICATING BEARINGS

receptacle . When a tumbler bearing has to be lubricated , the feeding—i n should be so arranged as to avoid loss of oil through the tumbler moving out of the range of the hole , or pipe, or tray from which it drops . This is done by cast

o a ing a narrow tr ugh of appropri te length on the tumbler .

14 s a Fig . illu trates common design , with a cup on the higher bearing communicating by a groove with the hole

F s . 14 nd 1 5 . 1 r d a r et o d o f i g a T u m bl e r F i g . 6 . O in y M h B r a c k et T ro u gh s a n d Fe l t L u b r i c a t i o n o f T o p a n d B o t t o m P a d f o r S l i de V e rt i c a l J o u rn a l s

in the end hole . The groove comes under the end of the pipe through which the oil is fed , and never moves out of its reach .

In s ome of the more complicated designs of machines , specia l provisions are necessary to lubricate parts tha t are — i ll subj ect to frequent change of position slides sp ec ﬁca y.

e o This is seen , for example , in th p rtion of a grinding ma

70 LUBRICATING BEARINGS is counterbored to catch the drip from the edges of the hole

and lead it properly into the continuation hole .

r t of Fla t l d n u rfa c s L u b ic a io n S i i g S e . The lubrication of tables presents some variations in methods of supply and A e distribution . great deal d pends upon the size and

weight to be dealt with , and upon the speed of movement .

r A slow moving table o slide , or one subj ect only to occa

F i . 18 . C o nd dct i n T es r o o es a n d P a ss a es g o by u b , G v g si ona l alterations in position does not require so much lubricant as a rapidly moving one in which the oil is swept A off more quickly , or squeezed out by pressure . small table , such as on a cutter grinder , for instance , can be n oiled satisfa ctorily enough by the ca m , pouring o the sur faces while the table is run back . If the length prevents

- this being done , lateral oil holes are drilled , and vertical ones to communicate With the under side of the table face LUBﬁI CATI NG BEARINGS 1

- a r e r or , if V slides are used , diagonal holes drilled . G ooves

lm o or pads distribute the ﬁ evenly ver the surfaces , and pads have the merit of retaining a portion of oil and keep o ing the surfaces m ist for considerable periods . S everal such pads ca n be inserted in pockets in the slide ( see sec ti o na l 15 view, Fig . ) and the oil is then supplied by a pass

age to each pad .

- The location of the oil holes , plugs , or oilers is a matter

of importance in certain types of tables . In s o me grind

ing ma chines there is no obj ection , for instance, to drill

ing the holes vertically from the table top , and letting in

F i 1 9 . L r g. u b i c a t ing R o l l e r s f o r G r ind ing M a c h ine

plugs or spring caps ; but in other machines these areas might be covered for a long time with ﬁxtu r es or other

ﬁtti n s g , and there would be no chance to get at the aper x tures without removing the ﬁ tur es. Then the lubrication

might be neglected . The most effective method of lubricating a heavy table s or slide , such as that of a planer , a heavy haper, grinder ,

- or a boring mill , is to employ rollers sunk into oil pockets , thus forming an automatic devi ce independent of the care

of the operator , and providing a supply of lubricant at each

return of the table , or as fast as it is squeezed out . The 72 LUBRICATING BEARINGS primitive device is simply to ﬂoa t a wooden roller in the

- oil pocket , but it should have some means of attachment to prevent its r ising unnecessarily high after the table has Of passed . course , in rotating tables , as in boring mills , a roller would remain in the same position ; but , even then ,

e to deﬁnite it is w ll afford a pressure by springs , which will result in proper rotation and an increase in the amount

F i . 2 0. L | r c e g u b r i c a t ing R ol e s a n d W e l l f o r G r ind ing M a h in , s h o w ing A p p l i c a t i o n o f b o t h P l a in a n d V - gro o v ed R o l l er

n 1 9 r of o i l smeared o . Fig . illustrates the type of oller ﬂ at ﬁtti ng used in a type of grinding machines , for the and

- a the V ways , respectively . The wheels are mounted on ' - c cross p i n held in a c entral plunger, whi h slides up and

o d wn in a casing, being maintained in the normal position at the top by the coiled spring . In another type , frames B r e ate similar to those in Fig . 2 0, A and , a used to lubric the tables of grinding machines . Studs are screwed into

- S bosses at the ends of the oil pocket , encircled by prings , and receive the ends of the frame which supports the roller . LUBRICATING BEARINGS 73

2 This construction permits the plain roller ( Fig . 0, A ) to

be made without a break across its face . Although the

- V wheels do not reach right across the slope of the vee , this is a matter of no consequence , since gravity makes up for the deﬁci ency in this respect . Slides which are not lubricated across their bearing width by rollers or pads require grooves to distribute the oil properly . The aim in the disposition of these groo ves is to spread the o il nearly across the width , and numerous

methods are followed , although the results are much the

same . The precise arrangement may often depend upon the

o f - position and number the oil holes . In a vertical knee or

i . 1 r o s A r r a em e t s n F r a c es F g 2 . V a i u ng n o f O i l G r o o v es o l a t S u f

slide , with a single oiler at the center of the top edge , the h n grooves radiate from this oiler to t e right a d left . Fig . 2 1 gives three alternative dispositions for milling-machine

- tables moving horizontally . The zig zag style is a favorite - f one, and is used also largely on the bearing surfaces o circular tables like those in boring mills , carrying a sufﬁ cient supply of lubricant .

u b r c t n V rt c l nd s L i a i g e i a S pi le . Vertical spindles present some di fﬁculti es in regard to eﬁi ci ent lubrication which do not exist i n horizontal ones ; this is due to the inevi table tendency of the oil to run down and of the bearings “ out - quickly . Ring oiling is out of the question , and , if a co nsi d er a ble quantity of oil is required , pads must be used , or the oil must be kept in constant motion and supplied by helical 74 LUBRICATING BEARINGS

An raising grooves . ordinary method of supply is adopted in the vertical shaft illustrated by Fig . 1 6 ; the oil is poured i n, on the removal of the stopper , both through the central ﬂ i n hole and around the top of the shaft , thence o w g by the

e the bearing groov s around bottom and top j ournals . Wicks are employed extensively to conduct and distribute oil to ver tical bearings . If a reservoir of oil is close at hand , the wick can be brought direct from this , and piping is not required .

Felt pads are also used to retain the oil .

L u b ric ati ng Ve rtic a l G ri ndi ng Wheel S i ndle Bearing . In — p Fig . 2 2 there is shown a cross s ectional view of the wheel head of a B lanchard belt - driven vertical surface grinding machine ; and the design of the bearings for carrying the wheel spindle , together with the means provided for assur

fﬁ i n . ing e c e t lubrication , will undoubtedly prove of interest

- This entire wheel head is carried on a vertical slide , so that alignment of the spindle bearings is made entirely i ndep en

e dent of the slide . There are ball thrust b arings at both the lower and upper ends of this spindle ; and for carrying the radial load there is a bronze bearing at the lower end of the spindle and a radial ball bearing at the upper end . The great advantage of ball bearings in such a case is that they may bepacked with grease and housed in such a way that the grease is kept in the bearing and adequate protection is afforded against the entrance of grit and other foreign matter , which would abrade the bearings . With such an ar

e rangement , the bearings r quire practically no attention , provided they are furnished with the proper kind of lub r i cant which is chemically neutral ; that is to say , free from

e both acid and alkali . Attention is call d to the hemispherical seats on the races of the ball thrust bearings which ﬁt corre s o n i n : p d g surfaces machined to receive them . It is the pur pose of this arrangement to have the hemispherical surface on the race adj ust itself for slight inaccuracies in alignment

‘ or to compensate for slight strains which d evelop in the — wheel head , thus enabling the bearing to distribute the thrust load over all of the balls and a ssur mg efﬁci ent trans i m ssion of power . LUBM CATI NG BEARINGS 75

At the lower end of the spindle there is a tapered bearing which is arranged with the large end of the taper at the top , so that it is impossible to transmit any of the wheel thrust ' A be a to this bearing . Tapered bronze bushing can e sily

i F i . 2 P ro s o m a de f o r L r c a t o o f S d e B ea r s g 2 . v i i n u b i i n p in l ng o f V e rt i c a l S u r fa c e G r ind ing M a c h ine raised byt u r n i ng the threaded ring B to provide for taking up a nywear which develops between the spindle bearing a nd B its bronze box . This adj usting ring is turned by a spanner wrench and the bronze bushing is not split . The provision of means for delivering lubricant to this tapered 76 LUBRICATING BEARINGS

spindle bearing is particularly interesting . L ubricant is de livered to an oil reservoir C , from which it fl o ws down through a channel cut in the bronze bushing at the left-hand side of the spindle to gain access to the spiral oil - groove which is cut in the j ournal . Oil is carried up through this groove , and in this way a liberal supply of lubricant is always dis tributed over the bearing . U pon r eaching the top of the n bearing , excess oil fi ds its way into chann els at each side of the spindle and flows down through these channels into C B reservoir , where it is available for subsequent use . y

' L r n m n x F i g 2 3 . u b i ca t ing A r ra ge e t f o r a G ea r w i t h in a Ho u s ing

studying the direction of ﬂ o w , which is indicated by arrows a shown in this illustration , the reader will e sily obtain a per fectly clear idea of the way in which oil circulates through this bearing . The upper end of the spindle carries a threaded collar with springs D beneath , which press up against it with a force exceed i ng the weight of the revolving parts by at

ﬁve - B least hundred pounds . y this means , the thrust bear ing at the lower end , on which d epends the accuracy of the grinding, is always kept tight . All backlash in the spindle is eliminated and variations of spindle length with temper

ature are automatically corrected . The downward reaction

78 LUBRICATING BEARINGS the tubes into the bearings in order to provide an air-tight connection . It is not essential that the wicking should touch the shaft , although it should extend very close to i t . The tubes should be fastened to the bearings at an angle of

9 0 degrees with the pressure sides , with reference to the direction of rotation of the shaft , as shown by the arrow . “ — - s f f n Be r n s — Type o Sel oili g a i g . The so called self oil ing” type of bearings may work on either of two principles Oil may be taken from a reservoir and carried up to the bearing by any suitable means , or the bearing box which

- w e L ca t o i s 2 5 . I T e o f B ea r s r e r F i g. S e f o i l ing y p ing h u b i i n effect e d by C a p i l l a ry Act i o n surrounds the j ournal may be impregnated with some form of lubricant . The latter type of bearing is often referred to

“ ” as an oilless bearing , although in many cases it is found desirable to give bearings of this type perhaps 2 5 per cent of the quantity of oil which would be required for the eth ci ent operation of a bearing of standard design . The great advantage of self—oiling or oilless bearings is that they do n not require as much attention as the ordinary type , and i the event of neglect to supply such bearings with the quan tity of lubricant which they are expected to receive , they are capable of operating for a considerable length of time without serious damag—e . D d l r f r 2 o ge Capil a y Sel Oiling Bea i ng . In Fig . 5 there is shown what is known as a capillary type of self—oiling bear LUBRICATING BEARINGS 79

li nesha f ing, which is suitable for use in t hangers and sim

i la r types of equipment . This bearing is made by the Dodge f M M g . Co . , of ishawaka , Ind . The bearing box has been

designed with an opening at the bottom , in which there is inserted a wooden block that extends down through the box for a su fﬁ ci nt distance so that the lower side of the block can dip into an oil reservoir provided in the bearing ho u s

ing . The block is held against the shaft by a spiral spring , and it has a series of slots sawed in it which come to a sharp

angle at one end . It is the tendency of the oil to rise in the

F i 2 D r m st r a t P r c e o er i er a t g . 6 . i a g a i ll u ing in i p l g v n ng O p i on o f C a p i l l a ry B ea r ing

narrow end of these slots in the wooden block , as a result of capillary action , which is responsible for carrying oil up

to the bearing . Perhaps a better idea of the arrangement will be secured

2 - after referring to Fig . 6 , which shows a cross sectional

View of the wooden block , illustrating the way in which it

- is slotted , and a cross sectional view through the bearing showing how the oil is drawn up in the narrow side of these

slots in the wooden block , due to the capillary action which

- l has j ust been mentioned . A uniform ﬁ m of oil is main

ta i ne - d on the shaft in this way , and oil grooves are cut in the bearing box in order that these grooves may be kept

‘ As full of oil , thus facilitating lubrication of the bearing . there is no m echa nci a l agitation of the oil contained in the 0 LUBRICATING BEARINGS

i reservoir in this bearing , any fore gn matter which is pres ent in the oil is allowed to settle to the bottom , so that only pure oil is admitted to the bearing and no trouble is exp er i enced through grit or other foreign materials rapidly wear ing the bearing surfaces . The reservoir in this bearing has su fﬁci ent capacity to contain a supply of oil which is adequate to keep the bearing efficiently lubricated for a B period of six months . efore replenishing the supply of oil , the bearing should be thoroughly cleaned , and this r e sult is easily accomplished by removing the drain plug at the bottom of the r eser yo i r and ﬂ u shi ng the entire bearing with kerosene , after which the plug is replaced and a fresh supply of oil placed in the bearing .

B r nz Bu s n w t Pr v s n fo r ut ma t c o e hi g i h o i io A o i L u bric atio n.

- Another type of self oiling bearing is shown in Fig . 2 7 , which is especially adapted for use in loose pulleys and similar installations where it is desirabl e to have the combi nation of a bronze bearing box and provision for automatic M B lubrication . This bearing is made by the occasin ush ing C o . , of Chattanooga , Tenn . It will be seen in the illus

tr a ti on , which shows the method of mounting this bearing , that an oil reservoir is provided in the hub of the loose f pulley , and the principle by which lubrication is ef ected is quite similar to that of the bearing furnished with a wick , M through which oil is drawn by capillary action . occasin bushings can be used in any type of machine member furnished with an oil cavity from which lubricant can be drawn by the capillary oil - feeders which are contained i n holes that pass transversely through the bushing so that they come into contact with the bearing surface in the manner shown on the inside of the bushing . They deliver a continuous supply of oil to the bearing , and are so pre pared that they cannot glaze or clog . It is claimed that these bearings prevent the waste of oil , in addition to supplying the bearing with exactly the desired volume of t oil which is required for its efﬁci en operation .

il B t r rf s O a hs fo r S u bmergi ng Bea i ng S u ac e . Submerged lubrication , that is by running parts in a bath of oil or LUBRICATING BEARINGS 81

, grease which they continually stir up and spread over themselves , exists in many forms . In the oil bath as cor r l ect y arranged , there is never any lack of lubricant and the chief care is to see that no sediment is thrown u p , or that any parts are shielded from the spread of oil . The familiar worm -gear and spiral gear drive running in an oil trough was followed by the geared drives in which other class es of gears are caused to dip in oil and splash it over

- the teeth . Fast running gears necessitate com plete covering to pre vent the oil from ﬂying

” out of the box ; but , in

- worm gears , it is not always necessary to a f ford absolute p r o tec tion , as , for instance , where the trough is situated withi n a fram ing , and dust or grit cannot enter . A half trough I S all that I s i . B r B s r d w g 2 7 . o nz e u h ing p o vi ed i t h t M ea ns o f a u t o m a t i ca l ly d r a w ing O i l hen required , When , f r o m S u p p ly R es e r v o i r however , the box is sit u a ted in the open , complete enclosure is usually desirable . The action of gears running in an oil bath can be some times utilized to lubricate the adj acent bearings as well , in fitti n place of g separate oilers to these . Care , however , must i n be taken that these bearings receive a su ffic e t amount , which is not always the case in badly designed boxes . The oil which is thrown up by centrifugal force to the roof of the box may have to be defl ected by various arrangement s so as to direct it into the oil recesses above the bearings . Sometimes a passage is made in the casting to lead down t to these points , or ribs are cas or screwed on to catch 82 LUBRICATING BEARINGS the flyi ng oil and let it run down and drip at the place n ni n required , without actually co fi g it in grooves ; or a piece of piping, or bent wire may be fitted and arranged to accomplish a similar function . O ccasionally , a strip of metal is attached and sloped in such a manner that the oil i is thrown against t, and thence off at an angle to the bear i ing , or to a channel communicating with t . The ideal method of lubrication for the bearings in gear boxes on machine tools and other bearings , where such an arrangement is possible , is to have the gears run in a ll d reservoir fi e with oil . This not only avoids excessive wear of the gear teeth , but it also provides for ample lub r i i n ca t o of the bearings by the splash system of lubrication .

- Oil holes may be provided at the top of the bearings , so that oil thrown from ' the gears drops into these holes and provides a continuous ﬂ o w of lubricant through the bear

e ings . Where this arrangement is employed , an ampl amount of lubricant can be put into the reservoir to last

for several weeks , the length of time being governed by

A - the conditions of service . gage glass on the reservoir shows the level o f the oil , and at infrequent intervals it is f merely necessary to replenish the supply o oil . When gears are running in mesh , or when a shaft is rotating in f its bearing , the ef ect of friction is to tear o ff very ﬁne fragments of metal which collect in the oil in such a

“ ” reservoir ; also , there is a tendency for a muck to collect

‘ in the bottom of the reservoir , due to oxidation of the oil .

For these two reasons , and also owing to certain other causes , it is necessary to clean out the oil reservoirs a t

intervals of about six months . To facilitate this cleaning process , a drain plug should always be provided at the bottom of the reservoir which can be screwed out in order

“ o ff e to drain the dirty oil . The reservoir should then b ﬂ u shed out with kerosene to clean away all accumulations of metal particles and oxidized oil , after which the drain plug is replaced and the reservoir r eﬁlled with clean oil .

B r n s l ea i g Oi e d by the S plash System . An example of the splash method of lubrication is shown in Fig . 2 8 , which LUBRICATING BEARINGS 83 illustrates the table gear bracket of the vertical surface B grinding machine . y building this mechanism as an inde m si m li ﬁ d pendent unit , the process of anufacture is p e , in addition to making provision for the efﬁci ent lubrication of the gears and bearings by application of the splash system of oiling . The drive is transmitted through a spline shaft

A and bevel gears to the table gear B . Oil is retained in reservoir C at the level indicated by shaded lines , and the bearing of the spline shaft is lubricated by the ring- oiling principle , which will be more fully discussed in connection B with another example of bearing design . y this method ,

F i 8 t d o f r c t T ea r B r a c k et o f Ver g 2 . M e h o l u b i a ing a b l e G t i c a l S u rf a c e G r ind ing M a c h ine ring D runs over the bearing to be lubricated and i ts lower side dips into the oil carried in reservoir C . Rotation of

r n D the shaft results in continuously tu n l g ring , with the result that oil is carried up by the ring and deposited at the top of the bearing , thus delivering a constant supply of A E lubricant to the bearing . felt packing is employed to exclude abrasive dust , which would soon wear out the bearing if special precautions were not taken to prevent it from g etting between the rubbing surfaces ; and tele sc0pi c tubes form an effective seal at the right-hand end of the shaft . When it is required to clean out reservoir C by the method which has already been explained , drain plug F is withdrawn in order to provide for the escape of dirty 8 4 LUBRICATING BEARINGS

ﬂ u shi n oil from the reservoir . and the g out of the reservoir with kerosene so as to remove all accumulated foreign

matter before a fresh supply of lubricant is added . For lubricating the bearing of the vertical shaft carrying gear B , oil is delivered through channels communicating with a felt packing G which is in contact with the bearing of the vertical shaft . This packing serves the double pur pose of carrying a continuous supply of oil to the bearing and ﬁlter i ng out any foreign matter with which the oil may have become contaminated . Any excess oil which passes through this bearing is caught in the lower reservoir and replenishes the supply of oil for lubricating the gears and

- the ring oiled bearing of the horizontal shaft . Felt pack ings are Very generally used in this way to provide for de livering clean oil to bearings of grinding machines and similar equipments where the bearings are so situated that it is di fﬁ cu lt to exclude abrasive dust and other substances that would rapidly score and wear out the bearings if they came in contact with the rubbing surfaces .

' Flooded L u bric atio n . Pump systems embody many ar rangements of a v a r i ed character for the thorough dis

tr i buti o n of the lubricant . In the most complete gear

— - boxes , and in some machines notably all geared milling machines—the same supply is utilized to ﬂ o o d the gears

o and bearings , being pumped up fr m the well at the base

and falling from a p erforated pipe in cascades on the gears ,

while suitably arranged pipes conduct it into the bearings . the The top part of each bearing i s cast as a trough , and one below it catches the oil that runs out from the ends or

center hole of the bearing . Grooves , holes , chutes , and pipes are employed to assist in the conduction .

When geared feed - boxes were ﬁr st developed for use on Milwaukee ” milling machines built by the Kearney

Trecker Co Milwaukee , Wis . , it soon became apparent

, tion . After studying the merits of various methods the

- design ﬁna lly adopted consisted in constructing oil tight

8 6 LUBRICATING BEARINGS

is reduced to practically the absolute minimum . In ordi

- nary practice , the oil grooves are closed at the ends to prevent the escape of oil from the bearings , but in the present case the grooves are cut right through to provide for a free circulation of oil and the washing away of all for ei n g substances from the bearings . On 2 0- inch all -geared drilling machines built by the B D R C o . arnes rill , ockford , Ill all bearings , with the ex ce ti o n - p of the spindle sleeve and cross spindles , are con ti nu o u sl y oiled by an automatic lubrication system . Oil is delivered by a geared pump in the reservoir of the machine and distributed constantly to all gears and bearings , includ

- ing the crown gears and feed box . This automatic lubrica tion system is manufactured under license from the Kearney

o A Trecker C . close view of the mechanism of one of the B arnes drilling machines is shown in Fig . 30, and the

- geared p ump , which is driven by the constant speed driving shaft , will be seen at the bottom of the oil reservoir . Oil is drawn into this pump through a strainer , which is also

the located at the bottom of reservoir , although it is not shown in the illustration . There is a valve which can be set with j ust enough resistance to lift the required volume of h oil to the crown gear bearings , while t e remainder of the ' h i l- oil o v er ﬂo w s directly into t e o hole for the rear bearing . “ The pipe which will be seen j ust underneath the back bone of the machine , leading up to the crown gears , has small holes drilled in it j ust above each of the bearings in order that oil may escape to provide for the constant lubr i A cation of bearings on both of the diagonal shafts . groove is cut inside of each double bearing which leads the oil u fﬁci en across to the lower diagonal shaft . A s t volume of oil is delivered to the crown gear housing so that the over

- ﬂow runs into the feed box , from which it works down

- through the worm shaft bearing , and in so doing oils the

- the worm and worm wheel , after which it is led back into frame of the machine and cascad es back to the original the reservoir . In this way , every bearing , aside from

- spindle sleeve and cross spindle bearings , is automatically supplied with a constant stream of oil . LUBRICATING BEARI NGS 87

t d il nks E v O T . le a e a In very large machines , when a

ﬂo o ded considerable quantity of oil has to be. through bear

r f a ings and over su cs, a head is sometimes obtained by the use of an elevated tank , from which pipes lead down to the various grooves or passages . The pump then replenishes

0. r s o f o r C o t o s L r c a t o o f ea rs a nd F i g. 3 P o v i i n n inu u u b i i n G B ea r ings o n V e rt i ca l D r i l l ing M a c h ine

ﬁl r the tank at the required rate , the oil being te ed before returning . Any blocking of the long pipes should be pro vi ded agai nst by the inclusion of pet - cocks at suitable posi tions , close to the bearings , so that the position of an oh A struction can be discovered . part from this method of obtaining a large supply , the tank is also often embodied in portions of machines to feed certain details that are 88 LUBRICATING BEARINGS

maccessi ble - either by an oil can , or are too numerous for

individual attention , and there is thus risk of neglect . The

e ' oil either runs direct to the places n eded , or is fed slowly

. S o filled by siphon wicks long as the tank is , kept clean fitted from grit or dirt , and the wicks are properly, no 1 . 3 trouble can ensue Fig . illustrates a typical case , where o r i fices all the oiling are located close together , and the

pipes from the trough do not need to be carried far . As the trough is enclosed inside a column closed by the ﬁa h door no lid is needed to cover the oil , but this would be r e quired if the trough were situated externally .

31 . r nd P es s S e e r a B ea r s o ca t ed Fi g. T o u gh a i p u p p lying v l ing l i n P ro x i mi ty t o ea c h o t h er

L n sha t Oiling i e f Ha nge r Be a ri ngs . In shops where the \ i k l equipment is quite congested , it i s l e y to be found that there is danger of accidents to men whose duty it is to oil h the bearings of li ns a ft hangers , countershafts , and similar equipment where the bearings are placed in somewhat i n A accessible positions . little time given to the subj ect of

be th devising methods of lubrication may often x e means of saving serious accidents and consequent litigation over em :

’ lo er s p y liability . Observation of the following points will

' often result in saving trouble : Wherever possible , the work of oiling bearings in li nesha ft hangers and counter shafts should be done while the machinery is not running . A better plan is to equip such bearings with automatic lubricators which need to be ﬁlled only at infrequent i n ter va ls o ; with bearings of this type , it is always feasible t LUBRI CATI NG BEARINGS 89 arrange to replenish the supply of lubricant at some time when the machines are at rest . It will always happen , however , that certain conditions will arise , making it nec essary for shafting to require attention while the machines are running , and to meet such contingencies , safe means of access must be provided , among which mention is made of the following : Where ladders are used to r ea chli nesha fts and counter shafts , they should be provided with hooks or hangers to ﬁt over the shaft at the upper end and spurs at the lower

l ﬂ o or . end , which wi l insure obtaining a secure grip on the

With such provision , there is no likelihood of a ladder slipping and causing the workman to be thrown into mov ing parts of a machine . In big shops it will sometimes be found feasible to have a service platform or “ runway ” provided with guard rails and toe- boards running parallel h f to li nes a ts, so that any point on the shaft is readily a c M cessible . oving parts of machinery should not be allowed to proj ect over such a runway , but if such a condition is unavoidable , the moving part should be completely enclosed .

- In some plants , use is made of a car hung from an I beam l l n h running paral el to the i es a ft, and with such an equip ment the oiler can readily move along the shaft to reach all of the bearings . The use of such a car or of the service r str i ct platform is naturally e d to quite large shops . S ome shops have their men use forced -feed oil - cans of suffici ent length so that they can be operated from the floor . Where men are employed to look after the work of inspect ing and oiling shafting and other equipment before the regular starting time of the plant , accidents sometimes happen through the engineer ’ s starting up the machinery fini h before these men have s ed their work . This source of danger can be overcome by providing disconnecting a ppli anoes whi ch make it possible to cut out any section of the equipment until the work of oiling bearings has been com l p eted. Switches used for this purpose should be provided with padlocks , so that they can be locked in either the open or closed position . If such appliances are not i n 9 0 LUBRICATING BEARINGS

stalled , it is good practice to require a man employed in oiling equipment to report personally to the engineer of the plant that he is going to oil certain machinery . Probably the best safeguard in the lubrication of bearings used in all inaccessible equipment is to adopt the use of ” one of the so - called self- oiling types of bearings which can be furnished with a supply of lubricant that is adequate for a considerable period of time . B earings of this type are furnished with means of drawing oil from the reservoir and delivering it to the bearing surface , so that constant fﬁ ci en 1 and e t lubrication s assured .

r s Oil G oo ve fo r Beari ngs . In order to provide for uni form distribution of oil over the entire surface of a j ournal bearing it is common practice to cut what are termed “ oil

grooves in the surface of either the j ournal or its box . These grooves are usually made in the form of a spiral or

some kind of an endless curve , as shown in Fig . 32 , which illustrates bearing boxes made by the B unting B rass

B ronze Co . , Toledo , Ohio . Special machines are made for

- cutting oil grooves , which provide for handling this work in a more expeditious manner than is possible with hand tools or on machine tools of standard design . There are several reasons for cutting oil - grooves in the form of spirals or other curved shapes , instead of adopting the practice of cutting straight grooves parallel to the axis of the j ournal . If such a practice were followed , there would be a tendency for oil to gather in the grooves near the bottom of the box , while those on the sides and top would

- remain empty . With oil grooves of spiral or similar form , however , this trouble is not experienced and rotation of the j ournal has the further tendency of circulating the oil

“ through these curved grooves , thu s greatly facilitating distribution of the lubricant . The oil should be introduced at that point where the forces acting tend to separate the A shaft and box . t this point grooves must be cut in the surface of the box , so as to distribute the lubricant evenly i n over the entire length of the j ournal . Having been so tr o duced and distributed , the oil will adhere to the j ournal , LUBRICATING BEARINGS 9 1 and be carried around by it as it revolves to the point

where it is pressed against the box with the greatest force , thus forming the lubricating ﬁlm which separates the rub

bing surfaces . The supply of lubricant thus continually

furnished , and swept up to the spot where it is needed , must a not be diverted from its course in any w y. A sharp edge

Ma chi nery

i 32 . a m es o f B r B r B s i F g. Ex p l o nz e ea ing u h ings s h o w ng D i ffer ent Fo r ms o f O i I -gro o v es

at the division point of the box will wipe it o ff t he j ournal

as fast as it is distributed , or a wrongly placed oil groove will drain it out bfo r e it has entirely accomplished its pur

. As pose generally cut , oil grooves have two faults ; ﬁr st, they are so numerous as to cut down to a serious extent the

area of the bearing , and , second , they are so located as to

allow the oil to drain out of the bearing . As f ew grooves

should be used as possible . LUBRICATING BEARINGS Two classes of bearings which may well be made without

ﬁr st - e oil grooves are , , the cross h ad slippers of engines ,

- and , second , crankpin boxes . The cross head slipper should have a recess cut at each end , in the same way as the count

r o r i n he - e b g of t two part box . The best way to oil a crank

pin is through the pin itself . In the case of overhung pins , a hole is drilled lengthwise of the pin to its center . A second hole is drilled from the surface of the pin to meet the ﬁr st A one . shallow groove should now be cut in the surface of the pin , parallel to its axis , and reaching almost to the

No ends of the bearing . grooves should be cut in the boxes , but the edges where they come togethr should be counter bored . As much care and attention should be given to the oil grooving as to the size of a bearing , yet it is a matter

the f a nc ﬁt it s . often left to . y of the mechanic who The purpose of the grooves , to distribute the oil evenly, should ever be kept in mind , and no groove should be out which does not accomplish this purpose , except it be to return waste oil to a place where it may again be of use . As a rule , bearings have too many grooves and , far from assist ing the lubricants , they generally drain the oil from where it is most needed .

9 4 DESIGN or PLAIN BEARINGS tool spindle bearings must ﬁr st consider the conditions under which the bearings are to operate with the idea of f u lﬁlli ng these requirements without tendency for the bear

e ings to wear exc ssively .

After this has been done , it is necessary to take steps to work out the design along such lines that convenient means are provided for readily taking up any small amount of

wear which may develop in the bearings . Only after pro . Vision has been made for maintaining an accurate ﬁt b e tween the spindle and its bearings can the designer turn his f l attention to the question of transmission ef iciency , a

f l lle though this condition must also be u ﬁ d. There are often special conditions which must be considered in designing bearings in order to assure satisfactory operation . For instance , on grinding machines , trouble would almost surely be experienced through abrasive dust from the wheel find ing its way into the bearings and causing them to wear ex cessi vely, unless the housings were designed with special provision to exclude dust and other foreign matter from of the bearings . This is an example special conditions likely to require careful consideration in working out the design of bearings capable of giving satisfactory service . A Ge nera l Pri nciple s Co ve ring Bearing De sig n. j ournal should be designed of such a size and form that it will run

cool , and with practically no wear . The question of both heating and wear is one of friction , and in order to under stand the principles upon which the design of bearings

should be based , the underlying principles of friction must

ﬁne ﬁr st be understood . Friction is de d as that force acting between two bodies at their surface of contact , when they are pressed together , which tends to prevent their sliding one

‘ e upon the other . The energy used in overcoming this forc of friction appears at the rubbing surfaces as heat , and is ordinarily dissipated by conduction through the two bodi es .

o f. e The force of friction , and hence the amount heat gen r

i r m n ated under any given c cu tsa ces, can be greatly reduced by the introduction of an oily or greasy substance between the rubbing surfaces . The oil or grease seems to act in the DESIGN ( OF PLAIN BEARINGS 9 5

t same way that a great number of minu e balls would , redu e the ing friction and wear , and thus preventing the overheat

e t n ing and consequ nt destruc ion of the parts . O this account ,

all bearings are always lubricated . Thus the question of

j ournal friction involves the question of lubrication . For the purpose of understanding as far as possible what

goes on in a bearing , and the amount and nature of the

forces acting under different conditions , several machines m have been designed to investigate the atter . In general , they are so arranged that a j ournal may be rotated at any

e . desired spe d , with a known load upon the boxes Suitable means are provided for measuring the force of friction and also the temperature of the bearing . From investigations with such apparatus , it has been found that the laws of fric tion of lubricated j o u r na ls differ very materially from those

o - c mmonly stated in text books as the laws of friction . Frictio nal Resist a nc e i n L u b ric a ted a nd Unlu b ricated

Bea ri ngs . It is generally stated that the force of friction is proportional to the force with which the rubbing surfaces

e are press d together , doubling , or trebling , as the case may

e be, with the normal pressure . This law is perfectly tru

’ lubr i for all cases o f unlubricated bearings , or for bearings ca ted e with solid substanc s , such as graphite , soapstone ,

e l tallow , etc . When , howev r , the bearing is properly u br i ca ted with any ﬂuid , it is found that doubling the pres

sure does not by any means double the friction , and when the lubricant is supplied in large quantities , by means of an

he n e oil bath or a force pump , t frictio will scarcely incr ase

at all , even when the pressure is greatly increased . From the experiments of Thurston , and also of Tower , it appears that the friction of a j ournal per square inch of bearing

surface , for any given speed , is equal to

“ f hp ( 1 ) = where f the force of friction acting on every square inch of bearing surface ; p the normal pressure in pounds per square inch on that surface ;

k a constant . 6 DESIGN OF PLAIN BEARINGS

i t The exponent depends on the manner of oiling , and 1 varies from , in the case of dry surfaces , to in the case of drop -feed lubrication ; or thereabouts in the case of ring and chain- oilers and pad lubrication ; and b e comes zero in case the oil is forced into the bearing under sufﬁci ent u press re to ﬂoat the shaft .

The second law of friction , as generally stated , is that the

force of friction is independent of the velocity of rubbing . tr he This law also is for unlubricated surfaces , and for sur faces lubricated by solids . In the case of bearings lubr i ca ted i by oil , the friction ncreases with the speed of rubbing , E but not at the same rate . xpressed as an equation : m f kv ( 2 ) where f the force of friction at the rubbing surfaces in pounds per square inch n: a constant ; 1) the velocity of rubbing in feet per second .

The exponent m varies from zero , in the case of dry sur

- faces , to in the case of drop feed , and in the case of an oil bath .

The third law of friction , as it is generally stated , is that the friction depends , among other things , on the composition of the surfaces rubbed together . This , again , while true for unlubricated surfaces , is not true for other conditions . No te matter whether the surfaces be s el , brass , babbitt, or cast iron , so long as they are perfectly smooth and true , they h will a ve the same friction when thoroughly lubricated .

The friction will depend upon the oil used , not on the ma ter i a ls of j ournal or boxes , when the other conditions of speed and pressure remain constant . Many people think that babbitt has less friction than iron or brass , under n the same circumstances , but this is not true . The reaso

“ for the great success of babbitt as an anti - friction metal depends upon an entirely different property , as will be ex plained later . Combining into one equation the different laws of the friction of lubricated surfaces f kp n vn

8 DESIGN OF PLAIN BEARINGS

e in which p bearing pressur , in pounds per square inch ;

1) r velocity of rubbing , in feet p e second . C constant having values varying from 8 00

- foot pounds per second , in the case of iron

- 2 60 or low carbon steel shafts , to 0 foot

- pounds , in the case of high carbon s teel

crankpins . This formula is satisfactory for bearings running a t ordi

m o i ﬁ nary speeds , although it must be d ed for extrem e cases . The results obtained from the machines for testing bear ings a r e very even and regular for ordinary pressures and

e temperatures , but when either of these is increas d to a high point , the friction and wear of the bearing suddenly h ‘ increases enormously . T e reason is that the oil has been

e e sque zed out of the bearing by the great pr ssure . This squeezing out of the oil and consequent great increase in the f friction has three ef ects . The absence of the lubricant

h e causes the parts to scratch or score eac oth r , thus rapidly destroying themselves , the great increase in friction results in a sudden very high temperature , in itself destructive to ‘ the materials of the bearing , and the heating i s generally so rapid as to cause the pin and the interior parts of the box to expand more rapidly than the exterior parts , thus causing

e the box to grip the pin with normous pressure . When the a oil has been squeezed out in this m nner , the bearing is said

“ ” to s eize . t il Infl u e nce of Qu ali y o f O . The unit pressure which any bearing will stand without seizing d epends upon its tem

er r h The a p a tu e and t e kind of oils used . lower the temper

ture of the bearings , the greater the allowable unit pressure . The reason for this is that oils become thinner and more

- ﬂ owi n free g at the higher temperatures , consequently they

e re are more easily squeezed out of the b aring , and it is mo

l n e likely to se ze . O this account , the higher the v locity of

rubbing , the less the unit pressure that can be carried , but it does not follow that the allowable unit pressure varies inversely as the speed of rubbing , as . was formerly thought .

- ﬂ i The thicker and less free o w ng an oil is , the greater the DESIGN OF PLAIN BEARINGS 9 9 unit pressure it will stand in a bearing without squeezing out . A watch oil or a light spindle oil can be used only under a very small unit pressure . Sometimes they are squeezed

B ea ri n g P r essu r es fo r V a r i o u s C la sses o f B ea r i n gs (K i m ba ll a n d B a r r )

C la s s o f B ea r i ng a n d C o ndi ti o n o f O p er a t i o n

B ea r ings f o r v er y sl o w sp eed a s in tu r n ta bl es

r in b r idge wo k . . B ea r ings fo r slo w sp eed a n d inter mittent lo a d a s in pun ch p r esses L o co m o tiv e wr i st-pin s L o co m o tive cr a nkpin s L o co m o tiv e d r iving j o u r n a l s

R a ilwa y ca r a xl es . . n a va l p r a cti ce a r e e e a b ea r M in ngin m in ings . m er ch a n t p r a ctl ce M a r in e engin e cr a nkpin s * S ta ti o n a r y engin e m a in b ea r ings fo r d ea d l o a d ( high sp eed ) fo r stea m l o a d S ta ti o n a r y engin e cr a nkpin s o v er hung cr a nk

$ ( high sp eed ) 1cen ter cr a nk S ta ti o n a r y engin e wr i st-pihs ( high s p eed ) * S ta ti o n a r y engin e m a in b ea r ings fo r d ea d l o a d ( slo w sp eed ) fo r stea m l o a d S ta ti o n a r y engin e crankpin s ( sl o w sp eed ) S ta ti o n a r y engin e W r i st-pin s ( sl ow sp eed ) Ga s e es a ea r s ngin , m in b ing Ga s e s e cra s . ngin , nkpin

Ga s e t- es wr s s . . ngin , i pin Hea vy li nesha ft b r a ss o r B a bbitt lining L ight li nesha ft ca st-i r o n b ea r ing su r fa ces r G en e a to r a n d D yn a m o b ea r ings .

‘ ei ht o f sha h el c W g ft , ﬂ yw e s , et . out of the bearing when the pressure does not exceed 50 pounds per square inch . A cylinder oil of good body will stand a pressure of over 2 000 pounds per square inch in o the same bearing . It is imp rtant to determine , if possible, in each case , what quality of oil is best adapted to each par 1 00 DESIGN OF PLAIN BEARINGS

i nfl u enci n ti cula r hearing . A third cause g the pressure which may be carried is adhesiveness between the oil and the rubbing surfaces . Some oils are more certain to wet metal surfaces than are others , and , in the same way , some metals are more readily wet by oil than are others . It is r evident that when the surfaces repel , ather than attract , l the oil , the fi m will be readily broken down , and , when the h film opposite is t e case , the is easily preserved .

s Calcu la ti ng Beari ng Dime n io ns . The durability of the lubricating film is affected in great measure by the character of the load that the bearing carries . When the load is un varying in amount and direction , as in the case of a shaft fl h l l carrying a heavy yw ee , the fi m is easily ruptured . In those cases where the pressure is variable in amount and film direction , as in railway journals and crankpins , the is much more durable . When the j ournal rotates through only

- a small arc , as with the wrist pin of a steam engine , the cir cumsta nces are most favorable . It has been found that when all other circumstances are exactly similar , a car j ournal , w here the force varies continually in amount and direction , will stand about twice the uni t pressure that a ﬂ he l i 11 yw e j ournal w , wher e the load 1s steady l n amount and A direction . crankpin , since the load completely reverses

- for every revolution , will stand three times , and a wrist pin , where the load only reverses but does not make a complete revolution , will stand four times the unit pressure that the ﬂ h l yw ee j ournal will . The amount of pressure that commercial oils will endure at low speeds without breaking down varies from 500 to

1000 pounds p er square inch , where the load is steady . It is not safe , however , to load a bearing to this extent , since it is only under favorable circumstances that the ﬁlm will stand this pressure without rupturing . On this account , j ournal bearings should not be required to stand more than

- two thirds of this pressure at slow speeds , and the pressure

r o i should be reduced when the speed increases . The a pp x mate unit pressure which a bearing will endure without seiz i ng is as follows

DE SIGN OF PLAIN BEARINGS

There are a few cases where a unit pressure sufﬁ ci ent to lm break down the oil ﬁ is allowable . Such cases are the

e pins of punching and sh aring machines , pivots of swing bridges and similar constructions , where the motion is slow

e e and heating cannot w ll result . In such cas s , pressures up

4 er to 000 pounds p square inch are permissible .

- r High s peed Bea i ngs . In carefully lubricated high

speed bearings , very high unit pressures are permissibl e. The following ﬁgu r es represent the practice of a large con cern building electrical machinery in large units : Velocity in feet per s econd of rubbing surfaces 2 0 30 4 0 60 75 Permissible pressure in pou nds per square inch 1 6 5 1 9 0 2 05 2 2 5 2 30

The permissible pressures here incr ease with the speed .

th h e The reason for this is that e higher t e surface spe d , the more eff ectively is the lubricant dragged in against the hy

e - draulio pressure due to the load carri d , the high speed bear ing acting in a measure as a pump for its lubricant .

m t r f ft r i Dia e e o Sha o P n. The diameter of a shaft or pin must be such that it will be strong and stiff enough to carry

e the load . In order to d sign it for strength and stiffness , th e approximate length must be known . This will be as sumed from the following equation 2 O W V N

PK i n which L length of bearing in inches ; W total load upon bearing in pounds N number of revolutions of j ournal per minute ; P and K same quantities as in E quation ( 5 ) When the approximate length has been found by the use

of this equation , the diameter of the shaft or pin may be found by the general formulas for the strength of materials . The length of the j ournal must then be recomputed by the formula given i i i the next paragraph .

r Length of Bea i ng . Having obtained the proper di a meter , a bearing length must be selected long enough so DES I dN OF PLAIN BEAR INGS 1 03

e that the unit pressure shall not xceed the required value . This length may be found directly from the equation

in which L l ength of b earing in inches ;

W 2 total load upon bearing in pounds ;

‘ — P K N f s a me E 5 , , , and D j quantities as in quation ( ) Should the length obtained by this formula not give p r a c

tical dimensions for proper proportions , the diameter and length of the bearing must be adj usted to meet the condi A tions . good rule for the length of the j ournal , after the

R ela t i o n o f L engt h 1 t o D i a m et er ( 1 o f J o u r n a ls

T yp e o f B ea r i ng V a l u es o f

Ma r in e en gin e m a in b ea r ing s 1 to M a r in e engin e cr a nkpin s S ta ti o n a r y engin e m a in j o u r n a l s to S ta ti o n a r y engin e cr a nkpin s S ta ti o n a r y en gin e cr o ss-h ea d pin s . Or din a r y h ea vy sh a fting wi th ﬁ xed b ea r ing s Or dina r y sh a fting with selfa dj u sti n g bea r in gs G en er a to r b ea r i n gs

requirements with relation to the bearing pressures have

th the e been met , is to make e ratio of l ngth to the diameter about equal to of the square root of the number of revo lutions per minute . This quantity may be decreased from 1 0 to 2 0 per cent in the case of crankpins and increased

i in the same proport on in the case of shaft bearings , but

e should not be departed from too wid ly . In the case of an 1 00 engine making revolutions per minute , the length of

r e the bea ings would , by this rul , be from one and one

- the e quarter to one and one half times diam ter . In the case 1 000 of a motor running at revolutions per minute, the bear

b e ings would about four diameters long . This rule , while it

cannot be adhered to on all occasions , is an excellent guide . O4 DESIGN OF PLAIN BEARINGS

A bearing may give poor satisfaction because i t is too

s long, as well as because it is too short . Almo t every bear ing is i n the condition of a loaded beam , and , therefore , has

eﬂ ti n some d ec o . Take the case of an overhung crankpin , in order to examine the phenomena occurring in a bearing

ﬁr t under these circumstances . When the engine is s run , both the pin and box are , or should be, truly round and cyl

ndr i l ﬂ c i ca . de e ts As the pin under the action of the load , the pressure becomes greater on the side toward the crank l throw , breaking down the oil ﬁ m at that point , and causing heat . After a while the box , therefore , becomes worn to a

slightly larger diameter at the side toward the crank . The i fl box , as already mentioned , must be a tr e larger in di a meter than the j ournal , and , for successful working , this f n dif erence is very strictly defi ed, and can vary only within l narrow limits . Should the pin be too large , the oil fi m will n be too thin , and easily ruptured . O the other hand , should the pin «be too small the bearing surface becomes coneen tr a te d at a line , and the greater unit pressure at that point film ruptures the . This is also the case when the pin is too long . The box rapidly wears large at the inner end , and , consequently, the pressure becomes concentrated along a film line . The lubricating then breaks down , and the pin The heats and scores . remedy is not to make the pin longer , t so as to reduce the unit pressure , bu to decrease its length and to increase its diameter , causing the pressure to be evenly distributed over the entire bearing surface .

t n D m ns ns fo r e r n s Example s of Calc ula i g i e io B a i g . A few examples will serve to make plain the methods of d esigning bearings by means of these principles . E xa mp les : Design a collar thrust bearing for a 1 0- inch 1 propeller shaft running at 50 revolutions per minute , and with a thrust of pounds . Assuming that the thrust rings will be 2 inches wide , their mean diam eter will be 12 E 5 inches . From quation ( ) the allowable bearing pressure

I S 2 00 $ 700

12 $ 1 5 0 7 00

1 06 DESIGN OF PLAIN BEARINGS

ma el 30 h a r o xi t . 7 i nc es, p p y 8 00 $ 12 00

E xa mp le : Design a crankpin for an engine with a

- e 2 0 inch steam cylinder running at 8 0 revoluti o ns per minut , and having a maximum unbalanced steam pressure of 1 00 h pounds per square inch . T e maximum and not the mean steam pressure should b e taken in the case of crank and

- the wrist pins . The total steam load on piston is 1 1 P e 2 00 000. B pounds . will be tak n as , and K as y Formula ( 6 ) 2 0 $ $ V 8 0 4 3 e . or say , 4 inch s 1 2 00 $ 1 000

In order that the deflecti o n of the pin shall not b e su ffi cient todestroy the lubricating film

3 i“/ 7 D WL which limits the deﬂ ecti o n to inch . Substituting in

e o r e . this equation , the diam eter becom s , say , inch s

the e t the e With this diameter , obtain l ng h of b aring , by using Formula ( 7

or say , 9 inches . 12 00 $ 1000

The mean of this value and the one obtained before is

e the about 7 inch es . Substituting this in the quation for 1 n w e 5 . e diameter , D 4 inches Substituting this diamet r in E quation ( 7

2 or say, 7 inches . 12 00 $ 1 000

It would now be preferable to take about half an i nch o ff

e the length of this pin , and add it to the diamet r , making

it inches , and this will be foun d to bring the ratio of the length to the diameter nearer to one - eighth of the square root of the number of revolutions . s o v er co m C ha rt fo r S afe Lo a d o n J o u rna l Bea ri ng . In ing the friction between a j o ur na l and its bearing , a certain DESIGN$OF PLAIN BEARINGS 1 07 1

amount of energy is expended in the form of heat , as pre vi o usl y explained . The only means of getting rid of this

heat is by conduction from the heat generating surfaces ,

through the masses of the shaft, bearing and bearing sup

port , and thence by radiation to the outside air . The oil t o a certain extent serves as a medium for the transfer of a part of the heat generated , by giving up its heat to the walls of the oil chamber ; but by far the greater part is dissipated h e by conduction in t e manner d scribed .

100 200 3—00 400 500 600 700 LOAD O N B EARING POUNDS PE R INC H O F LENGTHJ VI GC M n GTII

C u rv e g iving S a fe L o a d p e r In c h o f B ea r ing L engt h

Inasmuch as there is always som e heat generated in the bearing , no matter how liberally it may be design ed , there

e must always be a t mperature increase in the bearing . If

o this heat can be carried ff as fast as it is gen erated , the bearing will at some time in its operation r each a constant temperature . As the radiating capacity of any bearing is x a ﬁ ed quantity , the temperature reached will depend on ' a i s en er a e the rate t which heat g t d ; therefore , in order that

a bearing may not overheat , there must be some means of

ﬁxi n determining this rate , and g a limit to which the amount

of heat generated may be carried . B etween bearing sur faces , as in all cases where relative motion takes place be 1 08 DESIGN OF PLAIN BEARINGS

tween two surfaces in contact , the work done in overcoming friction depends on the rate of motion and the pressure m i existing between the two surfaces . This is o d ﬁed to a cer

tain extent by the character of the surfaces in contact , but i n for practical purposes , it is su fﬁc e t to consider the two

e factors of spe d and pressure , and as the work done is pro t portional to each it is propor ional to their product . B y ﬁx ing the product of these factors as a constant , we have a means of limiting the work done in the bearing to a safe quantity . It has been found by observation of a large number of b earings that were known to operate within a temperature 4 0 rise of degrees C . that if the rotative speed is taken in

feet per minute , and the pressure in pounds per square inch of proj ected b earing area , the constant lies between the limits of and If we use the smaller number and let

e (i diameter of bearing in inch s , = e l l ength of bearing in inch s ,

L total load on bearing in pounds , L P = . load on bearing per inch of length , l

N e r volutions per minute , we have ,

1TdN L

12 which reduces to NL

o r NP I

From this we see that if the product of the revolutions per minute and the load on the bearing per inch of length does not exceed the bearing will operate within the tem B e p er a tu r e rise specifi ed . y plotting these factors , the a com panying curve was obtained , which presents this formula in B a convenient shape for use . y reading across to the curve

1 1 0 DESIGN OF PLAIN BEARINGS

The allowances of some manufacturers are much smaller than those given in the table , as indicated by the following “ ” formula : The allowance made for the running ﬁt of the D 1 box and shaft should be about ( ) inch , where

D is the nominal diameter of the shaft in inches .

Fr t n l ss s in B bb tt B a nd R r ic io a Lo e a i , all , olle Bea ri ngs . In order to determine the relative power consumption for babbitt, ball and roller bearings , a series of tests was made and the results given in a paper by Carl C . Thomas , E . R . M L . E A . K aurer and . elso , presented before the American M E Society of echanical ngineers . The obj ect of these tests was to ascertain deﬁni tely the relative and absolute amounts of power required to drive a sp ecially constructed li nesha ft carrying given loads at certain known speeds of revolution , when supported suc cessi v ely by the three different typ es of shaft b earings mentioned , and to determine co efﬁ ci ents of friction for each type . Twenty bearings of each type were used in order

e that representative results might be obtain d . The design of the apparatus was made with the assist ance of the manufacturers of the bearings to whom pre

liminary drawings were submitted , and during the four years of the tests representatives of these ﬁr m s visited the laboratory for the purpose of giving whatever advice and assistance was possible . The preliminary work , covering

r the ﬁ st two years , showed the necessity of considering the temperature of the oil ﬁlm in the babbitt and roller bear

e ings , and it was only aft r careful study of the temperature question with regard to all three types that satisfactory r e

n ll su lts were ﬁ a y obtained .

t r t s De s c riptio n of Te s i ng Appa a u . The apparatus con sists of 2 5 feet 1 0 inches of li n esha fti ng in ﬁve equal sec tions , mounted in hangers which are inverted and used as

8 - I - ﬂoor stands . The hangers are bolted to two inch beams

o r which a r e leveled upon the ﬂ o . The shafts are of cold E 5 e . rolled steel , 2 inch s in diameter ach section is feet 2 inches long ; the adj acent sections are coupled to gether by means of a ﬂ exi ble leather disk or two straps DESIGN OF PLAIN BEARINGS 1 1 1

ﬂ n connecting the two a ge couplings . The ﬂ exi ble couplings prevent transmitting any part of the load applied on one

e shaft , to either adj oining s ction , and also prevent binding between shafts and bearings due to possible lack of alignment .

A direct - current Fort Wayne motor is directly connected

ﬂ exi l to one end of the shafting by means of a b e coupling . The motor is of the interpole type with the interpoles r e moved , making it a shunt motor . Its rating with the inter 2 poles is horsepower , 8 amperes , revolution 2 30 per minute , four pole, volts . The power required to a c run the motor alone at all speeds , without load , was cu r a t l e e y asc rtained , as well as the power required to run the motor and shafts together , at all loads and speeds . The relative amounts of power required to overcome the friction bf the various types of bearings were therefore accurately determined . The load was applied through levers having hardened knife edges and pin points as fulcrums . Across the top of

- I - the 8 inch beams and at right angles to them , are bolted

- - short 6 inch I beams to which the fulcrums are attached .

Standard 1 000- p o u nd scales are set upon the 6 - inch I

e e beams . A doubl system of l verage is used in order to get su fﬁci ent load upon the bearings with as short a length of lever as possible . This double system of levers also serves to steady the apparatus and prevent excessive Vibration . A pressure ratio of at each b earing to one at the scale was obtained . This was checked by an independent method of weighing the actual load resulting at the bearings , from

' a given load on the scales . The loads were applied to the shaft by two bearings between each pair of hangers . These bearings are identical with thos e in the hangers , and are supplied with knife edges which engage a V- shaped groove

- I - e in the 5 inch beam levers . The b earings and hang rs for each secti on are symmetrically placed with respect to the middle of the section ; therefore , equal loads on the inter mediate bearings produce equal pressures on the end bear

e ings . The reason for using twenty b arings was that the a mount of power necessary for a single bearing wa s so 1 12 DESIGN OF PLAI N BEARINGS

small as to be difficult of measurement ; moreover any single bearing might not truly represent results that would be ob

i e ta ned from that type of b aring in general .

h n s st T e Beari g Te ed. The three kinds of bearings tested were : the Hess - B right ball bearing manufactured by

-B Mf - the Hess right g . Co . ; the ring oiled bearing manu fa c u r e Mf t d by the Dodge g . Co . , lined with babbitt metal made from their formula ; and the Hyatt roller bearing

manufactured by the Hyatt Roller B earing Co . All bear ings were for the same size shaft and the same pieces of

shafting were used for all the tests , except that two sec

tions bent during the tests were replaced . The babbitt bearings are 9 inches long and hence their proj ected

area is square inches . These bearings were oiled

- - by the well known ring oiler device , there being two rings

in each bearing . E ach roller bearing contains six right

- hand and six left hand rollers , inch in diameter ; six / are 9 9 1 6 inches long and six are 9 inches long . The bearings are of the type in which a cage is used for hold

- ing one half the rollers . E ach ball bearing contains a single

set of balls inch in diameter . The diameter of the

inn er race across the ball groove is inches . Mercury thermometers (two in each babbitt and roller beari ng, and one in each ball bearing) were used for meas

e uring the temperature of the oil or bearing . In ord r to avoid the endwise thrust of the shaft , when supported by b the roller bearings , it was necessary to interpose two all thrust collars . B efore this was done , excessive vibration of the motor and of the apparatus resulted from the ten deney of the shaft to move endwise . This was particularly troublesome at high loads and speeds .

Pro cedu re whe n Maki ng Te sts . The power was m eas ur ed by the ammeter voltmeter method . A second ammeter was used as a check on the ﬁr st ; and a watt- meter ( ar ranged for direct and reverse readings ) as a further check . The general order of taking data was as follows : Clean the commutator ; adj ust motor to speed ; take all power readings ; read all thermometers ; adj ust speed again and

1 14 ‘ DESIGN OF PLAIN BEARINGS

t w r ns u m t n Rela ive Po e Co p io . A comparison wa s made the of the power consumed by friction in babbitt , roller and ball bearings for bearing temperatures of 1 00 degrees and F 77 degrees . , respectively . The power required for the

babbitt bearings is higher than for the other bearings , ex

cept perhaps at low loads and speed , and the power for

roller bearings is higher than for ball bearings . The ex

e cess of power for babbitt ov r rollers , and rollers over balls ,

increases with increase of speed for all loads . The table , “ R P ” elative Amounts of ower Consumed in Friction , shows the power consumed in friction by the three kinds of b ear ings at the speeds and temperatures indicated ; the relative e numbers are based , in ach case , on the average power for

C o m p a r i s o n o f C o efﬁ c i en t s o f Fr i c t i o n

C o efﬁ c i en t o f F r i cti o n

L o a d 72 7 P o ds L o a d 1 22 7 P o ds L o a d 1 72 P o u n , un , un , 7 d s

0 0 0 0 0 0 0 0

1 1 1 1 1 0 74 0 the three loads : 7 0, 2 0, and 7 pounds for balls ; , 12 4 0 174 0 730 12 30 1730 , and for rollers ; and , , and for babbitt . The co efﬁci ents of friction for the three types of bear

e 72 7 12 2 7 ings , when subj ected to av rage loads of , and 77 1 00 172 7 pounds , respectively, and temperatures of and “ Co efﬁci ents degrees F . , are given in table , Comparison of ” wa s 1 50 of Friction . The peripheral speed feet per

minute .

sts L u bric ant B rea kdow n Te . In order to observe the per f o r ma nce of the bearings under extraordinarily heavy

“ ” loads , breakdown tests were run on each type of bearing with only one section of shafting on which were four bear

ings . This small number of bearings was used because it was impracticable to keep clos e watch of a larger number

and avoid trouble during the excessively severe conditions . DESIGN OF PLAIN BEARINGS 1 1 5

600 The maximum load was pounds on the scales , or about

5000 pounds per bearing . A speed of 2 00 revolutions per minute wa s chosen because it represents about the average h li nes a ft speed in practice . These tests began at about

32 00 pounds per bearing . Failure occurred at about 4 2 50 4 pounds per bearing in the case of the babbitt , 650 pounds in the case of the ball bearings , and about 5 1 00 pounds in l the case of the rol er bearings . The quality a n d amount of lubricant used undoubtedly have an important effect upon the load that will cause a given bearing to fail . The bearings did not in any case fail structurally , as the power was cut o ff soon after dis tress was manifested , but the failure was simply that of the B lubricant . reaking down of the lubricant resulted in an immediate increase of the power required to maintain the original speed of rotation of the shaft in the bearings . In each case probably only one of the four bearings used in the breakdown tests showed distress at any one time .

In the case of ball bearings , distress was manifested by dis integration of the grease which “ melted ” and ran out of the bearing . This was accompanied by the immediate increase

r d r m n in power eq i e e t . Similar behavior on the part of the babbitt and the roller bearings indicated that at least one of the four under test was suffering from an approach to “ ” - - metal to metal contact . The bearings were not inj ured by these endurance tests , and all were used in subsequent tests at the more usual speeds and pressures .

1 1 8 INDE$

et o s o f r ca t 50 m h d lub i ing , Felt a s r ca t o b p d , lub i i n y, 55 o e s a s s ste 82 il d by pl h y m, F a t s r a ces r ca t o o f l u f , lub i i n , 70 o i l r o o es fo r 9 0 g v , F o o e r ca t o 84 l d d lub i i n , a es oi 9 3 pl in , d ign , Fr ct o a o sses i n a tt i i n l l b bbi , ba ll a t es o f 1 pl in , yp , a n d r o er ea r s 1 1 ll b ing , 0 r o s o fo r c ea 1 1 p vi i n l ning, F r i ctio n a l r esi sta n ce in lub r i ca ted r -o e s r er 59 ing il d di k g ind , a n d r ca te ea r s 9 5 unlub i d b ing , r -o r s f o r 62 g l g , g , Fr ct o co a r so f eﬁi in i in in i i n , mp i n o co ci t es o f se -o 7 8 yp lf iling , e ts o f fo r a tt a a n n , b bbi , b ll d B r e a r ess tests o n a tt r o er ea r s 1 13 in ll h dn b bbi ll b ing , eta s 4 3 m l , r o e 2 9 Gr ea se r ca t o 77 B nz , lub i i n , co o s t o o f 42 r w ee s i es ea r s mp i i n , G inding h l p ndl , b ing co ta co er ti n a nd ea fo r 4 n inin g pp , l d , , 39 r w ee s e ea r G inding h l pindl b ing, r o e ea r eta s 38 er t ca r ca t 74 B nz b ing m l , v i l , lub i ing ,

Hea t e er a t o o f ea r n , g n i n in b i gs, a i a r u r ca t o t e 77 C p ll y l b i i n , mul ipl , 9 7 — - C a a r se o ea r s , H s ee ea r s 1 02 pill y lf iling b ing igh p d b ing , D o e 78 dg ,

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o a r t r st ea r s 2 6 C ll h u b ing , Lea a n d a t o a o s oi 33 d n im ny, ll y , o er a t o a n d ti n a o s C pp , n im ny , ll y L ea a t o a nd ti n a o s o f d , n im ny , ll y , o f 34 , 34 er a t o ea a n d ti n C o pp , n im ny, l d , L ea a t o ti n a n d co er d , n im ny, pp , a o s oi 34 ll y , a o s oi 34 ll y , o er ti n a n d ea r o e co n C pp , l d , b nz L ea ef ect o f o n a b tt 45 d , f , b b i , a 39 t ining . L ea ti n a n d co er r o e co n d , pp , b nz ta 39 ining, D es a c e s e L i n esha ft a er ea r s o i ign , milling m hin pindl h ng b ing , il ng , ea r 9 8 b ing, 8

o f ea r s e er a r c es L a n o r a ea r s sa e b ing , g n l p in ipl o d o j u n l b ing , f , o er 9 4 a r t fo r 1 06 g v ning, ch ,

o f a ea r s 9 3 L o a o n th-r st ea r s 2 5 pl in b ing , d u b ing , t r st ea r a se o n r L r ca t rea o wn tests 1 1 4 h u b ing , b d p in ub i n b kd ,

i e- a e 011 r t ea r i s et o s o f c ple o f w edg sh p d L ub i ca ing b ng , m h d ,

ﬁ lm , 2 7 50

D e s o s o f ea r s ca l cu la t L r ca t e ces e a es oi im n i n b ing , ub i ing d vi , x mpl , 1 00 1 04 54 ing, ,

r e -o ea r L r ca t o a to a t c ro e D o dge ca pill a y s lf iling b ub i i n , u m i , b nz

s 78 s w t ro s o n fo r , 80 ing , bu hing i h p vi i INDE$ 11 9

e t a s 55 ess ea r s 1 8 by f l p d , Oill b ing , ﬂ o o ded 84 s fo r ea r s h , Oil upply b ing , ow ef r ea se r o s o fo r 77 fected 50 g , p vi i n , , t e ca a r 77 ta s e e a te mul ipl p ill y, Oil nk , l v d, 87 o f ﬂ a t s i s r a ces 70 lid ng u f ,

o f ert ca r w ee Pd i n fo r co ct r ca ts v i l g inding h l p g ndu ing lub i n , s e ea r 74 66 pindl b ing ,

o f er t ca s es 73 P a ea r s es n o i 3 v i l p indl , l in b ing , d ig , 9 s a s s ste oi 82 t es oi 1 pl h y m , yp , s er ed fo r ea r S U P P o w er co s t o r e a t e f ubm g , b ing n ump i n , l iv , o a ces 80 a tt a a n d r o er ea r f , b bbi , b ll ll b L r ca ts et o s o f s s 1 1 3 1 1 4 ub i n , m h d upplying , ing , ,

to ea r s 53 P r ess r e a o wa e o s er b ing , u , ll bl , in p und p fo r co ct n 66 s a r e c o n th r s r p iping ndu i g, qu in h , u t b ea s 2 6 ing ,

Ma ch e to o s a sta e ea r in l , dju bl b s fo r s es oi 3 Ra a ea r s 1 ing pindl , di l b ing ,

eta s a tt 35 o , 58 M l , b bbi , Ring iling

a tt ea - a se a n d ti n - a se a e to s r er ea r b bbi , l d b b ppli d di k g ind b

o a r e 4 3 s, 59 c mp d , ing hea r 2 9 -o ea r s r s fo r 62 ing , Ring iling b ing , ing , ea r co er c a 4 0 R o er a tt a nd a ea r s b ing, mm i l , ll , b bbi b ll b ing , ea r sce a eo s) 4 7 r ct o a o sses i n 11 0 b ing , mi ll n u , f i i n l l , ea r tests o u 4 8 b ing, ,

se ea r a o s 32 S . A . E . sta a r a tt eta 3 u d in b ing ll y , nd d b bbi m l , 7 w te 2 9 c e e c r e the 2 2 hi , S hi l u v , ,

‘ a ne s e ea r n e -a st ert ca ea r n s Milling m chi pindl b i g S lf dju ing v i l b i g , 8

es 9 S elnf-a ea r s 1 d ign , ligning b ing , e -a s e ea r s 5 S lf ligning pindl b ing , i l a o wa ce fo r etwee sh a t e -o ea r s t es o f 78 O , ll n , b n f S lf iling b ing , yp , a n d o r a e a n d h a t o r i n a eter o f i n h h j u n l in m dium S f p , di m , ig

-s ee ea r s 1 09 s ee ea r s 102 high p d b ing , p d b ing , co cte w c s 64 o ea r s 1 ndu d by i k , S lid b ing ,

str t o 52 e ea r s se -a 5 di ibu i n , Spindl b ing , lf ligning, i nfl u en ce o f a t o i 9 8 a s s st e o f r ca t ea r qu li y , Spl h y m lub i ing b a t t o f 51 s 82 qu n i y , ing , a t s fo r s er ea r te ea r s s e fo r ht Oil b h ubm ging b ing S p b ing , impl , lig s r a ces 80 t 22 u f , du y, cts s ec a 65 S ub - r ess s es a tt fo r 36 Oil du , p i l , p lid , b bbi , film we e-s a e t r st Oil , dg h p d , h u ea r es a se o n r b es a o w a ce fo r o i l et ee b ing d ign b d p in Ta l , ll n b w n ci le o f 7 s a t a nd o r a e p , 2 h f j u n l in m dium r o o es fo r ea r s 9 0 a n d h h -s ee ea r s 1 09 Oil g v b ing , ig p d b ing , li n esha ft h a er ea r s a o s se fo r ea r eta s Oiling ng b ing , ll y u d b ing m l , 88 co o s t o n o i 41 mp i i , r 58 a tt eta co o s t o s 35 Oiling, ing , b bbi m l mp i i n , , r s o r s s fi xed 63 3 Oiling ing di k , , 6 INDE$

ea r eta s sce a neo s es a se n b ing m l , mi ll u , d ign b d o p rin ciple o f 4 8 we e -sh a e o i l ﬁlm dg d p d , 2 7 ea r ress res fo r a r o s o a ou 2 5 b ing p u v i u l d ,

c a sses o f ea r s 9 9 Ti n a t o a nd co er a l b ing , , n im ny p p , llo y s r o es co o s t o o i 4 2 o f 34 b nz , mp i i n , ,

o efﬁ i ents o f r ct o co a r T i n a t o a nd ea a o s c c f i i n , mp i , n im ny l d , ll y

so n o f fo r a tt a a nd oi, 34 , b bbi , b ll T i n t r e r s 1 1 4 , a o , ea a nd co er . oller b a ing , n im ny l d pp a f r ct o r e a t e a o ts o f o s o , 34 f i i n , l iv m un ll y Ti n ea a n d co er r n n er co s e i n b a b , l d pp , b o z e co p ow n um d , by 3 tt a a n d r o er ea r n s ta ining. 9 bi , b ll ll b i g , Ti n s st t tes fo r ea r 1 1 3 , ub i u , in b ing eta s 42 o r a s re a t o n o f e th to m l , j u n l , l i l ng a eter 1 03 di m , Vert ca ea r s se -a st i l b ing , lf dju ing, t r st ea r s a o wa e r es h u b ing , ll bl p 8 sure in p o und s p er s qu a r e ert ca s es r ca o n o f V i l pindl , lub i ti , h 2 in c , 6 73 a s o i l e e a te 87 T nk , , l v d ,

T est g p o wer co su p t o o f Wea r i n b ea r n co ensa t o in n m i n i g, mp i n n r a tt , a a d r o er ea fo r co ress ea r b bbi b ll ll b , by mp ing b ing s 1 1 0 ing , b o x 1 4 ,

ests r ca t r ea o w 1 1 4 co e sa t o fo r ra w T , lub i n b kd n , mp n i n , by d ing r st ea r s 1 2 1 2 5 s e to ta ere b o x 1 5 Th u b ing , , , pindl in p d , a o wa e r es s r e o s W h te eta 2 9 ll bl p u in p und i M l , er s a re i ch 26 W c s o i l co cte 4 p qu n , i k , ndu d by, 6

MACHINERY ’ S

Hi gh- gra de M echa nic—a l B oo ks a t On e D olla r a C opy A N ew P ri ce to M eet N ew Conditi ons

MA CH INERY a nn oun ces a new a n d or igina l ser i es o f D o ll a r s o n est a t o o a er set a n d r t m ech a ni ca l bo o k b qu li y b k p p , p in ed in the best style a n d b ound in h a nd so m e a n d dur a ble r er s ese a r e o o s f o r r a ct ca men a t to ugh p a p e co v . Th b k p i l e a wo r k in th e indu str i es a s w ell a s f o r stud ents o i . m ch ni ca l e s—s o a t e a t cs a c e es s o r a ct ce subj ct h p m h m i , m hin d ign , h p p i h o a a e e t The a e s e i s 6 x 9 c es a n d s p m n g m n . p g iz in h o o o ta s r o 1 1 2 to 1 2 8 a es I n e er a n d ea ch b k c n in f m p g . v y d eta il th ese high -gr a d e bo o ks will be fo und equ a l to the m o st The lo w r ce i s a e o ss exp en sive publi sh ed . p i m d —p ibl e by h o lding ea ch subj ect d o wn t o a bso lute essen ti a l s 1 1 2 or 1 2 8 e — stea o f 300 a es T o eco o e a er a n p a g s in d p g . n miz in p p d r t co sts to a i s t o sa e s sta t a ese e o n o p in ing d y v ub n i lly . Th c es c the r ea t sa s a sa t s a cto r mi , in luding g ving in u ing i f y co v er sto ck in stea d of the exp en siv e clo th bindings u n a v o i d a e i n b o o s o f the s a t c ess he r e h bl k u u l hi kn , give t ea d r t e la test a n d best m ech a ni ca l liter a tur e a t a n unp r eced ented ’ r ce MA C H I NE RY s D o a r o o p i . ll B k s Will m a k e a grea t pla ce o f t e r o wn t he ﬁ eld o f ec a ca ter a t r The h i in m h ni l li u e. b o oks schedul ed f o r publi ca tio n in 1 9 2 1 a r e

MA C H I N E RY ’ S D O L L A R B O O K S

S o A r t m et c f o r t he a t h p i h i M c h ini s . S t o lu i o n o f T r i a ngl es . ea r -c t t a nd e a r -c tt a c G u ing G u ing M h ines . B r o a c P h ing r a ct i c e . C d er B r R m n o ea a d r d . yl in ing , ing, G in ing P a a nd C o t r o P r d l nning n l l ing o u ct i o n . m o m e t a a em e t a e S s t em s a n d R t E p l y n M n g n , W g y , a e S et t in g. B a a n d R r l l o l l e B ea r ings . B ea r s a nd B ea r ing ing M et a l s . P r c es of ec a cs nd t in i p l M h ni a S r engt h o f M a t er i a l s . P r a ct c P ro e m s i n a t e m a t c s i a l b l M h i . C t t C o m o ds a nd D s t r t u ing p un i i bu ing S yst ems . D i e C a s t ing . D r o Fo r a nd D r o Fo r D p ging p ging i es . M a c h ine Fo r g ing. B a c k s m t S o P r t l i h h p a c i ce. o d e r A re t ces s a n e e M n p p n i h i p d S h p T r a ining M t h o ds . r a a t o a n d a a e m - O g niz i n M n g ent o f M a c h ine b u i l d ing P l a nt s . A r t m et c e m e t a r A e ‘ i h i , E l n y l g b r a a nd L o ga r i t h m s . P r ec s o . a i i n G ge B l o c k s a n d M ea s u r ing M et h o ds .

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Fifty Cents the Co p y

I n thi s ser ies MA CHINERY str ikes the ha ppy m edium o f low s a t s ser es o r p r i ce a nd be t qu li y . T h i i c mp eh end s a wid e o f o r ta t ec a ca s ects ea ch o o e r a nge imp n m h ni l ubj , b k b ing

ete tse . h ese co a ct e e s o o co mpl in i lf T mp , in xp n ive b k s cover m ech a ni ca l subj ects with the sa m e d egr ee of ca r e a n d th o r o ughness b estowed upo n the co stli est tech ni ca l b o o k s ’ s e MA C H I N ERY S e o o s a r e r e a r e publi h d . Blu B k p p d by MA ’ C H I N ERY S own exp er i en ced s ta ﬁ o f engin eer s a n d wr iter s ’ a n a r e se a nd r te MAC H I N ERY s a The sta d t p in d in pl nt . nd a r d set f or t e i s e a ct the sa e a s f o r A I ER tse h m x ly m M CH N Y i lf . They co uld n o t b e p r o du ced a t a ll excep t i n l a r ge editi o n s s o n o te a th th e r o a r t A I E R ba ed a b s lu f i in i p pul i y . M CH N Y ha s e er s e a n s ccess o o a n d A I ER ha n v publi h d un u ful b k , M CH N Y s b een p r o du cing m ech a ni ca l litera tur e f or a qu a r ter o f a r centu y .

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