$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 .