Forging by Hydraulic Pressure.” by RALPRHART TWEDDELL, M

THE INSTITUTION

OF CIVIL ENGINEERS.

~~~ ~~ .~__ SESSION 1893-94.-PART 111.

SECT.1.-MINUTES OF PROCEEDINGS. 20 February, 1894. ALFREDGILES, President, in the Chair.

(Paper No. 271 0.)

“ Forging by Hydraulic Pressure.” By RALPRHART TWEDDELL, M. Inst. C.E. INthe following remarks on the history and application of the hydraulic press toforging large masses of steeland iron, the Author assumes that the ingots are of suitable quality, and does not propose to refer to the variousprocesses by which such quality is obtained. The hydraulic treatmentof steel in the ingot formed the subject of a Paper read before this Institution by Mr. W. H. Greenwood, M. Inst. C.E., in 1889.l For reasons therein stated, Mr. Greenwood confined his remarks to the effect of “ fluid compression ” on the ingot, and was unable to treat of the subject of this Paper. It may be takenthat the practical employment of thehydraulic forging-press dates from the successful production of steel in the form of large ingots ; and as in its day, N,asmyth‘s steam-hammer superseded machines of less power, SO the former has had to give place tothe hydraulic press. Much has been written as to the relative merits of the steam-hammer and the hydraulic press, but while there is room for diiference of opinion in reference to work of ordinary dimensions, there is none when it comes to a question of making the heavy forgings now required for large guns and marineshafting, and the hydraulic pressshows togreater advantage as the work to be dealt with increases in weightand complexity. The introduction of the hydraulicforging-press is due to Mr. M. __._____

1 Minutes of Proccedings hat. C.&vol. xcviii. p. 83. [THE INST. C.E. VOL. CXVII.] B

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 2 TWEDDELL ON FORUING BY HYDRAULIC PRESSURE. [Minutes of Gledhill,managing director of SirJoseph Whitworth and CO. About the years 1860-61, the firm in question had considerable trouble in obtaining steel suitable for the manufacture of guns. .So far as the artof steel manufacture was then understood, nothing could be alleged against its quality. It was this which suggested to Sir Joseph Whitworth the idea of subjecting this material to .a very high pressure when in a fluid state, his notion being that this compressioncould be applied not only to ingotsbut to .castings of all shapes. This, however, was not found practicable, and it was then that Mr. Gledhill suggested forging the ingot after compression in a suitable hydraulic press. The Author has taken some trouble to ascertain to whom the credit of so distinct :an advance in constructive machinery is due, and in support of this statement Colonel Dyer, of the Elswick Works, thus writes to the Author :- ‘L The introduction of hydraulic forging is undoubtedly due to Mr. M. Gledhill,who for manyyears hasbeen themanaging .director of the well-knownworks of SirJoseph Whitworth, of Manchester. He introducedthe system and perfected allthe details; if you apply to him he will supply you with the whole history of hydraulic forging. Everything which has been done as regardshydraulic forging both in Englandand abroad isan imitation of the system which Mr. Gledhill perfected.” It is generally understood that a similar system of forging is in use at Elswick, but the Author has not been fortunate enough to :see it in operation there. The Members of the United States Navy Gun-Foundry Board \thus reported theirimpressions on a similar occasion :- In speaking of the Whitworth establishment a8 unique, and of the process of manufacture at that place as a revelation, reference is specially made to the subject of forging. As to the assorting of iron and the treatment of the metal in the furnaces, there is no intention to draw distinctions ; but as to the treatment of the metal after casting, there canbe no doubt of the superiority of the aystem .adopted by Sir Joseph Whitworth over that of811 the manufacturers in the world . . . . It is only from personal observation that the merits of the system can be fully appreciated. The system of forging consists in compressing the liquid metal in the mould immediatelyafter casting, and in substitutingan hydraulic press for the hammer in the subsequent forging of the metal. . . . Afterdescribing in generalterms the mode of workingthe press, the Board proceeded to say :- The effect produced by it (the press) requires to be seen to be thoroughly appreciated,and is altogether differentfrom that producedby thehammer.

1 Report of the Gun-Foundry Board, Washington, Feb. 16, 1884, p. 14.

Theheated ingot resists the blow of the hammer,but the insinuating, persevering effort of the presscannot be denied. The longertime (several seconds) during which theeffort lasts, is a great element inits successful effect. As pressuresucceeds pressure, thestability of the particles is thoroughly distorted, and a veritable flow of metal induced, which arranges itself in such shape as the pressure indicates, the particles are forced into closer contact, and the whole mass writhes under the constraint which it is impotent to resist. The Board witnessed the operation of casting, followed by that of liquid com- preesion, the enlarging of hoops, the drawing outof cylinders, and the forging of .a solid ingot. The unanimous opinion of the members is, that the system of Sir Joseph Whitworth and Co. surpasses all other methods of forging, and that it gives better promise than any other of securing that uniformityso indispensable in good gun metal. The Author has quoted this Report because of its conciseness and the correctness of its forecasts, and because it exactly describes the effect (so far as it speaks of the process of forging) produced. on his own mind by a visit paid by him to the Whitworth works. It must beremembered also thatthe Reportrefers to a visit made ten years ago, and that many applications and advances in theintroduction of hydraulic forging-presseshave been made since that date. In 186l-about the time that Whitworth made his first press-John Haswell(an Englishman) introduced his hydraulic press into the shops of the Imperial and Royal State Railway at Vienna.This, however, wasnot a forging- but 8 stamping-press, and has been described as follows :- The system may be compared somewhat to forging in dies under the steam- hammer; but it permits the work to be finished much more accurately, and it also enables forgings to be produced which could never be otherwise manufac- turedunder the hammer. This mode of production offers theincalculable advantage of very great cheapness, and also the possibility to forge all details @ut of one piece, which it was necessary, formerly, to build up out of several .detached pieces, and lastly, their exceeding quicknessof manufacture. Haswell divided the classes of work which he proposed to do into four heads : 1. Sub-pressing with closed dies. 2. Sub-pressing combined with punching. 3. Pressing for drawingsteel (producing axles, .&C.). 4. For jumping-up and finishing parts of frames. The Author had some interesting correspondence with the late Mr. Haswell about twenty years ago, and there can be no doubt butthat to him is largelydue the present use of hydraulic pressurefor forgingand working metals.Mr. Haswell'sfree publication of his method of working,2 a.nd the results he obtained

'LThe Manufactureof Locomotive Details by Pressure: Haswell's system." By R. L. Haswell. Journal Iron and Steel Institute, 1876, p. 428. B2

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 4 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. [Minutes of abroad, undoubtedly did much to popularize the hydraulic system andto set other minds at work. The experimentsmade by Professor Tresca on the ‘‘ Flow of Solids ” undoubtedly also led manyengineers t.0 studythe question of forging scientifically, and indirectly assisted the introduction of the hydraulic forging- press. It is of course not difficult, and it is to some minds a congenialtask, to hunt for, and find, something in t,herecords of the Patent Office which may appear to anticipate the results obtained by anyonewho successfully introduces a new system. Ever since theyear 1846, whenSir Charles Fox proposed the attachment of different tools for the working of hot or cold iron to the tables of the Bramah press, many suggestions for its use as a forging-press have beenmade. Butwhile many people can make such suggestions, the actual carrying of them out is left to the few, and the Author trusts he has given the credit where it is due.

In order to ensure success in the application of the hydraulic press to forging, the following conditions must be fulfilled :- 1. The press must be so proportioned as to ensure the utmost rigidity, any movement of the main columns of course interfering with the correctness of the work. 2. The crane power must be not only ample, but so arranged that enormous weights, in many cases amounting to from 100 to 120 tons, can be manipulated by unskilled labourers. Hydraulic power, on the whole,seems to be the best to enable this to be done. 3. The details of the construction of such parts as the valves and pumping arrangements must be as perfect as possible. 4. A considerable amount of ingenuity and practical experience is required in making suitable tools for attachment to the press.2 Assuming that amaker has appliances for making the large castings, in many cases weighing 70 tons each, and steel columns, in some instances 26 inches diameter and 42 feet long and weighing say, 35 tons each, the first of the above conditions is perhaps the least difficult to fulfil. For the smaller presses, if sufficient thought is bestowed upon it, the design presents no great difficulties, and the simpler the arrangement the better the press as a working- tool. But it may be taken as an axiom thatthe greater the rigidity of the press, the better the quality of the work done by

Proceedings Inst. Mechanical Engineers, 1867, p. 114, and 1878, p. 301. * Minutes of Proceedings Inst. C.E., vol. lxxiii. p. 64.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. 5 it, and it is desirable to impart the power of the ram to the work in hand and not to distorting the press. The second condition, that of crane-power, ismet in various ways by different firms. As a rule, travelling cranes worked by steam are preferred,but in other cases hydraulic lifts areemployed to great advantage. In connection with this subject a great deal will depend upon the discipline and the organization of the men working the press. It is a curious fact that Nasmyth,l so far back as 1554, patented an arrangement of hydraulic cranes to ‘‘ facilitate the forging of iron,” which shows his wonderful grasp of the eonditions necessary for successful working. But in actual work the third condition is the most essential of all, and by far the most difficult to fulfil. A large hydraulic forging-press renders a very high working pressure of water necessary, in order to obtain the required power in a cylinder of practicable dimensions. The pressure varies between 2 and 3 tons per square inch, and with waterunder such pressures, working machinessubject to considerable shocks, it is very difficult to keep valves and joints tight. This difficulty is increased by the intermittent character of the working of these large hydraulic presses. An ingot weighing, say, 30 tons, will be twenty-four hours in the furnace, and perhaps require only an hour to be drawn down to the required shape in the press, and any practicable multiplication of furnaces will still leave the press idle, perhaps three-quarters of the‘ working day. On the other hand, when an ingot is once out and in the press, everyjoint must be tight and in order; otherwise the loss is great, and as a matter of fact the success of a press depends upon thesedetails. Mostof thesedifficulties aredue to waterbeing practically inelastic. This, while constituting its chief advantage for suchwork, involves an immediate loss of pressure if there is the slightest leakage. There is none of this trouble with the smaller presses, whichonly require a working-pressure of 50 or 100 atmospheres to obtain the necessary power. The various designs of forging presses will he described later, but to overcome this trouble withthe packingsand valves of large presses, several systems of working them have been devised, having different combinations of pumps and reservoirs. Amongst these are the following:- In the Whitworth press the movements of the main ram necessary to enable the ingot or other work to be adjusted, and of the lifting-cylinders, whose rams effect the return or upward stroke

~~~ -~

1 “ Machinery to Facilitate the Forging of Iron.” Patent No. 2744. 1854.

of the press, as well as the cranes and lifts used for taking the work to and from the furnace, are worked from an accumulator loaded to a pressure of about 2 tons per square inch. This ensures quickness of action. In orderzto control with ease and promptness the action of the forging-ram, the waterfrom the pumps is directed intothe ram-cylinder by closing an escape-valve : twovalves are employed, the largest of which is the main valve. When this. is raised thewater passes freelywithout acting upon theram of the forging-cylinder, and the engine is instantly relieved of the load. As already stated, the return stroke of the ram is then effected by pressurefrom the accumulator on thelifting-rams; and by suitable valves the engine is relieved from its load except during the periodwhen the forging-ram is actually squeezing; this work therefore is not done from an accumulator, but direct from the pumps. In the Davy press, water pumped into an air-receiver in which a pressure of 60 lbs. per square inch is maintained, is used for filling the main cylinder during the idleportion of its stroke, and is also in connection withthe suction Fig. 1. valves of the pumps. The pressure required I B-# to do the work is obtained direct from the pumps. Thelifting and return motions in the Davy press are also done direct from the pumps. In this case too, only the actual pressure re’quired needbe exerted bythe pumps ; a full description of this system is given in the Appendix. In the Walker press, the pressure-water required to effect the forging and to make the return motions of the press, is admitted direct from the accumulator; but arrangements are made to admit low-pressure water into the large cylinder whenit is descending and not pressing the ingot. In the form of press introduced by Messrs. Greenwood and Batley’ (Fig. l),there are, strictly speaking, no pumps used. The power necessaryto press the work isobtained! by means of what is termed a “ direct steam-driver.”2 This appd- ratus is well known under the name of an “ intensifier,” in which,

Transactions of the American Institute of Mining Engineers,vol. xxi. p. 321. 2 Proceedings Inst. Mechanical Engineere, Jan. 1878, pp. 45-66. “Pressure IntensifyingTApparatus-appliedto Hydraulic Presses.” By R. H. Tweddell.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TWEDDELL ON FORGINGBY HYDRAULIU PRESSURE. 7 a piston of considerable size is forced outwards. by either steam or water at a moderate pressure, and this being connected with a much smaller piston working in a hydraulic cylinder, the pressure in the latter is increased inverselyas the areas of the pistons. Sincethis ‘‘ directsteam-driver ” is only single-acting, after- the contents of one stroke are delivered into the forging-press, the latter will cease working until the high-pressure cylinder is. filled again. The chief merits claimed for this system are that it has no valves in the moving high-pressure column, and that it combines (though in both cases within a very limited range) the. properties of aforce-pump and an accumulator,without the trouble of the valves of the one and of the shock from the arrested

Fig. 2.

momentum of the other. On a similarprinciple is Mr. A. B. Brown’s hydraulic forging press, in which the main cylinder of the press is connected to a steam accumulator or intensifier, and to a discharge-pipe, for adjusting the highestposition of the main ram in combination with a valveless connection between the main cylinder and a hydraulic cylinder, in which works a small ram moved by a piston in the steam cylinder. In the Allen press 1 (Fig. 2), Mr. W. D. Allen has dispensed with a high-pressure accumulator, and with valves in the high- pressure water-column. In this press it is assumed that a low- pressurehydraulic system is alreadyin existence,such, for instance,as that used forworking a Bessemer plantat, say, 350 lbs. persquare inch. This pressure follows upthe idle

Journal Iron and Steel Institute, 1891, No. 2, p. 62.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 8 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. [Minutes Of portion of thestroke of themain ram, and the high-pressure connecting-pipe A between it and the fly-wheel pump B, is kept filled. The lifting is done by a steam-driven piston C connected with the main ram D. The so-called pump, which is driven by a fly-wheel, has no valves, and is, therefore, strictly speaking, not a pump at all. Thecontents of its cylinderare delivered direct into the cylinder of the preds, and on the return stroke of the press, the same,water is againsent back intothe pump. It is evident that the main ram rises and falls with each stroke of the pump, and has, therefore, a continuous up-and-down motion similar to that of a Ryder forging-press. This motion is, of course, only slight, as the area of the press-ram is much greater than that of the pump.Under these circumstances, of course, the pressure cannotbe maintained on the work.Many other schemes have been proposed to avoid the strains caused by the momentum of the accumulator, and yet retain some of its numerous advantages. So far back as 1845, Mr. Willianl Wylam, of Gateshead, patented an air-reservoir or accumulator to enable presses “to be worked at great speed, and atboth high and lowpressures.” In 1862, Messrs. Shanks,and Kohnpatented a forging-press with a steam-intensifier. Recently Messrs. Prott and Seelhoff hade introduced an arrangementwhich, while re- Fig. 3. tainingthe accumulator, uses an air-cushion instead of adead-weight, with the object of avoiding the shock. As theresult of seeing many large presses at work, the Author con- siders thatworking the press direct from ordinary pumps leaves little to be desired. The methods of generating the pressure for working the presses having been dealtwith, the different constructions or types of forging- presswill now be considered. Theywill be more fully described in the Appendix. Fig. 3 shows a type of press propose’d by Mr. Charles Fox in 1847. It is practically ‘a Bramah press with theforging-tools A aud B on top, and moving-tablesrespectively. Thisarrangement isnot variedin principle byputting thecylinder on the top instczdof on the bottom of the press. Such was the form adopted (Fig. 4) in 1861 by Mr. Haswell ; but he omitted the moving-table, which was not so pepeesary in that case; for, as already stated, the machine was more adapted to stamping or moulding than to forging.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. ~roceedings.1 TWEDDELL ON FORQING BY HYDRAULIC PRESSURE. 9 Forging involves in many cases the production of irregular forms from large masses of steel. Seeing that the ingot is generally of a rectangular shape, it requires considerable clearance to allow of its .being turned over between the top die and the anvil, which means a long, and variable working-stroke of the hydraulic-ram.

Fig. 5. I

Fig. 4.

! I

l l

!A I l l l 2 l I i ! l l ! I I I I ! I I i i I

But in the early days of hydraulic-presses, there were practical difficulties in obtainingmaterial strong enough for cylinder- castings of therequired length. This difficulty has now been entirely overcome; still, it may be of interest to describe one or two of the most ingenious means proposed to obtain the necessary clearance, whilst using a cylinderof short stroke.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 10 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. pinutes of Bessemer's specification of 1863 proposed to meet the requirements without the use of a long cylinder. This was effected as' follows :-A powerful screw B, Fig. 5, moves freely in a steel box let into the main casting A. By this screw the sliding-block C, to which the top die D is attached, is raised and lowered through therequired distance. Thehy- draulic-ram H carrying the anvil- block need only, therefore, move throughthe distance towhich the ingot is penetrated. In the Whitworthpress (Fig.6) the forging-cylinder A is carried in themoving table B, the different distancesrequired between B andthe bottom-casting C are regulated by means of nuts travelling on screws on the four columns, and attached to the top of thefour columns isa top- casting D. Thehydraulic lifting-cylinders and rams E E, by whichthe return stroke of the movingtable B carryingthe upper forging-tool is effected, are fixed to D. It isthus evident thatthe stroke of the forging-ramneed only beshort while the ram is exerting pressure on the work being forged. The resistance istaken up by thelocking-nuts F F on the columns G G, whichnuts are keptup to the faces of the moving-casting by suitable gear. It is evident in presses so made o! i( that but little lateral-stress can l I come upon the ram, owing to its short stroke. There are,however, manyiadvantagesin obtaining thisclearance without such complications-as adjusting-nuts and movable castings of great size. Supposing $he difficulty of obtaining a sufficiently

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TWEDDELL ON FORGING. BY HYDRAULIC PRESSURE. 11 strong cylinder of the required length to be overcome, the only remaining question is thatof relieving the rams from undue strain. In the Davy press of 1884, Fig. 7, this difficulty is overcome as follows :-The moving-crosshead A is guidedby means of the vertical beam B, which works in suitable guides between the two cylinders C C, in which two rams D D work and press on the cross-head A A through suitable thrust-blocks E E. The a.dvan- tages claimed for thisdesign are, that any side-stresses on the columns are to a great extent taken up by the vertical guide;

Fig. 7.

that with the tworams the stresses on themain-castings and cross-heads are better distributed; that work off the centre-line of the presscan be safely done;that with twocylinders for the same total power their size is reduced to more manageable proportions ; and that the press being narrower, the chain-blocks carrying the forgingCan be brought near to the anvil. In the Walker press, Fig. 8, on the contrary, the cylinder A is in the moving crosshead D D, the ram B being hed to the top main-girder C. Theguiding of thecylinder is thusprovided for, supposing that thecolumns are suEciently strongto withstand

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 12 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. winutes of the increased stresses dueto their extra length, on account of the movingcross-head containingthe cylinders, and the main- leather is easilyaccessible. In somecases Messrs. Walker use more than one psessure- .cylinder. Thereturn stroke is effected by means of lifting- cylinders E E attached in the usual way to the cross-head. Draw- ings of 2,000- and 5,000-ton presses are given in the Appendix. A press, Fig. 9, designed in 1885 by Messrs. Fielding and Platt, in conjunction with theAuthor, differs from any of those previously described. The three cylindersA A A are all below the floor level,

Fig. 9.

Fiq. 10.

and act by means of their rams B B B on the moving cross-head C C C ; connected with this cross-head are girders or bolts D D, which draw the upper block E and with it the top die E2 on to the forging which rests on an anvil-block G, supported by the stationary main castingF F. By this arrangement there is nothing to interfere with the free overhead-action of cranes or travellers, and as all the weight is below, the whole press should be very steady. The use of three ramsadmits of threepowers being readily obtained-no small advantage for a machine required to forge many sizes of ingots.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. ~roceedings.1 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. 13 All the designs for large forging-presses which have up to the present time been constructed or proposed are embraced by the preceding descriptions. By large forging-presses the Author means presses exerting pressures of 5,000 to 1,500 tons, or even 1,000 tons. But presses are now being constructed capable of exerting pressures of 10,000 tons, aIthough it is not quite evident for what class of work such a pressure will be necessary. There is, however, a large field fora much smaller class of forging-press, i.e. presses suitablefer use in smiths’ shops, and capable of exerting 30 to 150 tons pressure. It is not necessary to Fig. 11. describe themin detail.They are of two types, one withan open frontlike the ordinary steam-hammer, Fig. 10, in which A is the main frame, and B the hydraulic cylinder, whose ram C carries thetop tool. D is the anvil-block. In many cases a second hydrauliccylinder and ram E are added, in orderto A press atright-angles and allow of sectional moulds and dies being used, whilst in othersa bottomcy- linder G is sometimes introduced. Many such presses are at work ; the usualpressure being that employed by the Author in his system of hydraulic machine- tools, namely, one hundredat- mospheres. In additionto the above, a large number of presses of similar size are made of the ordinarytwo- or four-column type, some withthe ramsand others with thecylinders moving. Figs. 3 and 4 show presses with moving rams, and Fig. 11 shows a press for special work described many years ago by the Author.1 A is the cylinder moving on the stationary ra,m B-which forms part of the t,op crosshead C-which, by means of the columns D D,. is connected withthe bed-plate E. In some of these presses

~ * Proceedings Inst. Mechanical Engineers, 1874, p. 172.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 14 TWEDDELL ON FORC~INGBY HIDRAULIU PRESSURE. CMinutes of speed of 50 to 60 strokesper minute is obtained, so thatthe effect of repeatedpressures is combined with that of asteady squeeze. It is only by such presses as these, fitted with special valve- gear, that satisfactory welding is done, and the general idea that, however good a press is for forging or stamping, it is not equal to a hammer for welding, is no longer correct. The Author now proposes to consider the relative merits of the hydraulic press andthe steam-hammer. To thosewho have during the last ten years observed the gradual change of opinion on this subject, it seems almost to be slaying the slain to give reasons in favour of the use of hydraulic power.Some twenty years ago, in the course of a discussion on a Paper read by the Authoradvocating the use of hydraulic pressurefor forging, thelate Mr. BenjaminWalker, M. Inst. C.E., statedthat the prejudice against the introduction of steam-hammers into a new ironworks, in whichhe wasinterested, was so great that they were completelyexcluded in favour of the oldhelve hammer; in fact it was stated that good iron could only be made with the helvehammer. Subsequently steam - hammerswere admitted when it was found that not only could the iron be more easily worked, but that less skill wasneeded; the practicalreason of its superiority being that the work couldbe more easily dealt withby them than under the old helve. Verymuch the same class of objections were made to the introduction of the hydraulic press, and now its followers often overrate the advantages of the press and will hear nothing good of the hammer. As a matter of fact, so long as thesteam-hammer is powerful enough for its work it has the same effect on the material as a press, and owing to the sharp blow it can give, it possesses, in some cases, advantages over the latter. For example, in finishing off work the rapid succession .of light blows gives a finish to the work ; and in the case of welding, many forge-men maintain that the blow from the hammer expels dirtor scale, which in using the press is left in theforging. On the other hand, a large amountof satisfactory welding is done under the press, and the Author has seen a 40-ton press working up faggots satisfactorily from selected scrap into forgings for the best class of engine work. Butwhile there is still a large field for the steam-hammer for work of ordinary size, and for the preparation of work to be finished ,in a press, the hydraulic press is the only tool which

Proceedings Inst. Mechanical Engineers, 1874, p. 191.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TWEDDELL ON FORGING BY ECYDRAULIClPRESSURE. 15 canpractically be made of sufficient power toconvert ingots, weighing from 30 to 60 tons, into shafts, guns or armour plates. The hydraulic press became a necessity as soon as the effect of the steam-hammerwas found to be only skin-deep. This was notduo tothe action of the hammer, butrather to its want of size, and the well known“ awful examples ” generally given to show the different appearance of a forging acted upon by pressure and by impact, are approximately only correct if the hammer is not equal to its work. At the same time, it is certain that the steady effort of the press penetrates the forgingmuch farther than the blows of the hammer. This is wellillustrated in ordinary riveting, where the holes are completely filled by the rivet when hydraulic pressure is applied; while the effect of the hammer is chiefly expended in spreading out the heads. According toFairbairn, an ingot weighing 22 cwt., shown at the 1851 Exhibition by a Sheffield firm, was considered quite exceptional, ingots are now frequently cast weighing from60 to 80 tons. It is evident that the inertiaof such masses will absorb the blow of even a large hammer on its surface only, and in anycase a large number of blows is required, which means ltime and con- sequent cooling of the ingot. In the hydraulic press, so long as the pressure is maintained, the tool continues to travel, treating the huge steel ingot much as if it were a mass of putty. It must, however, be remembered that this steel ingot is perfectly homo- geneous, and the work to be done differs in character from that formerly required when large guns and shafts were made of iron, and builtup in pieces. Fairbairn wrote,] “Nothing could be better adapted than the steam-hammerfor building up a large mass by the union of successive portions, since the vis inertiae of the slabs to be welded on to the original core is not so great as to absorb the momentum of the falling hammer; hence a large portion of the power it acquires in falling is transmitted to the surfaces intended to be united. But in forging and shaping large masses of cast-steel, all these favourable conditions are reversed, and the .steam-hammer ceases to be an implement well adapted to the purpose.”

Having now referred to the history of the introduction of the hydraulic forging-press, tothe differentsystems of generating the force it is required to exert, and to some of the principal types ofpresses now used, theAuthor will in conclusion statethe

~ ~~~ “Iron; its History, Properties, and Processes of Manufacture,” 1865.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 16 TWEDDELL ON FORGING BY HYDRAULICPRESSURE. [Minutes Of advantages claimed for thehydraulic forging-press. Much thought has beenexpended in trying to calculate what size of hydraulic-press is equal to a steam-hammer capable of exerting a given force of blow. But it is hardly a question worth pursuing. In the Appendix are given the viewsof Mr. C. Davy, of Sheffield, a maker of both hammers and presses, and an abstract of some experimentsand observations by Mr.Coleman Sellers, M. Inst. C.E. ; but until the amount of work done on the forging is equal, and done in thesame space of time, no satisfactory comparison can be made. Professor Thurston, in the United States, has also gone into the relativeeffects of pressure and a percussive b1ow.l Owing to the action of the hydraulic press being constantIy progressive, the tool continuesto force its way into the ingot until resistanceits to alteration of form is equal to the pressure on the ram, or until the latter isremoved. In this it differs entirely from the action of a hammer, which,having delivered one blow, does no more work on the forging until the next blow is delivered. This constitutes the essential difference between the two machines. The effect of the hammer is momentary, and there is not time for the pressure it gives to penetrate the metal, much less to alter its form to any extent at one blow; but in the hydraulic-press the same rate of workingper hour canbe maintained, while the material is allowed every opportunity to%ow in therequired direction without injury. The effect of hydraulic-pressure on forgings is to increase their homogeneity. A leading firm in Sheffield informs the Author " that the tests got from pressed steel are a long way better than hammered steel." Whilethe blow of asteam-hammer isgiven withleast effect when it is most required,since it cannot get its full stroke until the forging is reduced in size, the hydraulic- press exerts its full power at any point in itsstroke. It may, the Author thinks, be taken as an axiom that waste of energyand noise areconvertible terms. The power of the hydraulic-press is practically all exertedupon the forging, and notdissipated in shocks tothe framing and foundations. This is easilyproved by the fact thatthe hydraulic-press is self-contained, and does notrequire foundations like those of the steam-haminer;and the effects of its blows arenot felt in the shopsor adjacent buildings. SirJames Eitson has said that the percussive force of the steam-hammer was of advantage in getting rid of the cinder in puddled iron, but with steel such violence is notrequired, in factundesirable, andhas been

Transactions Am. Soc. Mechanical Engineers, vol. v., p. 53.

Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. 17 therefore abandoned. A hydraulic-press occupies much less head- room than a hammer, and consequently travelling-cranes can be used, passing if necessary over the press. Not only can more work be turned out by a press than by a steam-hammer in a given time, but it can work through a much greater range; for, whilethe effect of a ‘‘ blow ” shortens the lifeof any of the tools or dies used, it renders impracticable the use of the numerousstamping-dies and moulds whichare satisfactory under a steady pressure. A great deal of other work besides forgingcan be done in the samepress by simplysubstituting suitable tools for flanging plates, punching large holes, bending armourand other plates, &c. But,apart from this,the art of forging large masses has made distinct advances since the introduction of hydraulic pressure ; for it was formerly impracticable to forge the hollow marine-shafts at present used, or to draw out gun-tubes or hoops on mandrils supported on suitable standards. It is extremely difficult to draw the line where such tools as have been described cease to be forging-presses, and become stamping- and welding-machines. Into such a category fall a vast. number of hydraulic-presses used for wheel-making, bossing and small glutting,forging-presses for wheels, and presses for stamping the iron-work in wagon-building works,&c. The Author has to acknowledge some valuable observations from Mr. Coleman Sellers, and others ; but the limited space at his disposal renders it quite impossible to discuss many interesting questions as to the relative effectof ablow or a steady pressure on the physical nature of steel. In other words, the Author finds he has to confine himself to the hydraulic forging-press only, and to eliminate the mechanical treatment of metals by forging orpressing as a whole. But a very significant fact in favour of steady pressure is the introduction of the compound steam forging-press by Messrs. Massey, the well- known steam-hammer makers. The hydraulic forging-pressis essentially an English invention. With hardly anexception, the Author has been allowed to see all the installations in this country; and there seems to be but one opinion as to the superiority of the hydraulic-press for all work whose size is beyond the range of the steam-hammer ; and in such cases its adoption may be considered as now practically universal. The Author has seen thepresses at SirJoseph Whitworth’s,Messrs. Tickers’, Sir John Brown’s,Messrs. John Spencer’s, and Messrs. Newburn’sworks, besides numerous smaller presses of 1,000 to 1,500 tons power. He, unfortunately, was not able to accept an invitation to see Messrs. Cammell’s press at work; but it is one [THE INST. C.E. VOL. CXVII.~ C Downloaded by [ University of Liverpool] on [15/09/16]. Copyright © ICE Publishing, all rights reserved. 18 TWEDDELL ON FORGING BY HYDRAULIC PRESSURE. [Minutes of of the largest in use, being occupied upon forgings for the 110-ton, 68-ton, andother heavy guns,gun-hoops of large dimensions. marineforgings, andthe largest steel armour-plates. Hydraulic forging-presses have been largely adopted on the continent ; but all the earlier, and many of the later, installations were sent out from England. Mr. R. M. Daelen gives as the general result, that when the working period and weight of output are considered, these presses performdouble theamount of work of a corresponding steam-hammer, with a lower cost of maintenance and fewer breakdowns.1 Thanks, however, tothe information so freelygiven to the Author by the numerous manufacturing firms mentioned in the Paper, the Institution is in full possession of all that has been done up to this date. Messrs. Breuer Schumacher have, however, kindly giren the Author, through theirmakers in England (Messrs. Greenwood & Batley)every information as totheir system of pumping- and accumulating-machinery for use with forging- presses. Thehydraulic forging-press, with its practicallyunlimited range of power, renders possible thecarrying into practice of many hitherto theoretical conceptions in constructive ironwork, owing to the facility with which the material can under it be forced to assume any desired shape. As an example, a press may be mentioned designed by the Author inconjunction with Messrs. Fielding & Platt, so far back as 1876, for makingthe Price- Willianw continuous steel crossing. In thiscase it was necessary to transfer the metal from one part of the crossing to another, which was done by means of additional hydraulic rams working on suitable dies.2 In conclusion, the Author trusts that this account of the capa- bilities of the hydraulic forging-press will encourage the adoption of bolder andyet economical designs in ironand steel con- str uction. The Paper is accompanied by numerous drawings, from which Plates 1, 2 and 3, and the Figs. in the text have been prepared.

1 ‘‘ StahI und Eisen,” 15th February, 1892, p. 155. Also Transactions Am. Iost. Mining Engineers,vol. xxi., p. 321. * Journal Iron and Stccl Institute, 1876, p. 428.

[APPENDIX.

APPENDIX.

DESCRIPTIONOF THE PLATES.

Plate 1.

Whitworth 3,000-Ton Forgiq-Press.-Fig. 1 illustrates a press prepared for forging a hollow ingot on a mandril with a turning motion attached to the latter. The press, so far as general design is concerned, is extremely simple, but is of massive construction, so as to insure accurate work. It consists of top and bottom main castings or entablatures, connected by means of four forged-steel columns, the moving tool being attached to a cross-head guided by these. The head of the press contains the cylinder in which the main ram works, and this ram has a sufficient length of stroke for all ordinary requirements. It will LW seen that this press is of much simpler form than the original design (Fig. 6). As previously stated, the press cannot be too simple in construction, and it is upon the details of the;valves and the general organizationof labour that success mainly depends. The press is shown in Fig. 1 forging a hollow ingot, and in Fig. la enlarging a gun-hoop. Davy Hydraulic Press.-Fig. 2 shows a general arrangement of a 2,000-ton press erected at Messrs. Spencer's works, Newcastle-on-Tyne. The horizontal pumping-engines work four ram-pumps, which produce the maximum pressure required without theshocks inseparable from the action of a loaded accumulator. The air-vessel is charged toa pressure of about 60 lbs. per square inchby means of a small auxiliary engine. The guided cross-head relieves the main cylinders of side stress, the load in effect being distributed between the cross-head and the entablature. The principal features of the design' are the use of two cylinders and main pressure-rams, which, with the two lifting-rams, are attached to a massive top entablature, while a still heavier set of girdera form the bottom or main bed- plate, connected to the top one by four steel bolts. The moving cross-head or tool-holder is 1-shaped, and at:the end of each of the lower arms are slide- blocks, which are bored to fit the four main columns. The arms are connected to the guide-blocks by simple ball-and-socket joints, in which a slight amount of play is allowed in order to accommodate the expansion that occurs when the cross-head becomes heated by proximity to a hot forging. For the same reason it is obviously impossible to connect the main rams rigidly with the cross-head, and therefore long spherical-ended thrust-rodsare interposed between it and the rams. Itwill be seen that the horizontal position of the cross-head is maintained eutirely by the columns andshank-guide; the lateral pressure on the rains is thereforescarcely appreciable, andadmits of aforging being placed considerably out of mid-position between the two rams without danger of grooving them. The use of two pressure-rams allows of lightermain girders being used.

I Engineering, vol. xli., p. 393. c2

The pumps arc single-acting ram-pumps driven from the crank-shaft, and as they are supplied with water at a pressure of about 60 Ibs. per square inch, very muchsmaller suction-valves arerequired with corresponding advantages in respect of leakage, clearance and renewals. The chief use of the low-pressure service of water, however, is in connection with the press itself, where it is used to promote the rapidity of action so much desired, and to prevent the infiltration of airinto the ram-cases and pipes. Thehydraulic pressure ranges from 4,500 Ibs. to an inch downwards, and is dependent on the resistance of the forging to compression. The main mm can, when desired, be put by means of large valves into direct communication with the low-pressure service. This is advisable when the clearance necessary to allow of' turning over the ingot has to be travelled before the full pressure comes on when the ingot is first actually pressed by the tool. Fig. 3 shows, in the form of a diagram, the action of thc valves, pumps and air-vessel. To describe the action of the valves, it will be most convenient to assume that the press-head is held suspended some distance above the forging by the lifting-cylinders, with the pumps at rest and all the valves in the position shown in the diagram. In this condition there is high-pressurewater in the lifting-cylinders due to the weight of cross-heads, rams, &C., resting on the underneath annular area of the pistons, on the annular surface of the valve A, tending to keep it open, in thepipes leading thereto, and in those from the toll of pilot valve R to the delivery-vahesof the pumps. To lower the press-head on to the forging, the valve R is opened by admitting pressure under the piston K, thereby lifting the valve R, and then allowingwater to escape from the lifting-ram cylinders. The water thusallowed to escape passes through the central partof the automatic valve A on to the main-ram cylinders along with a supply of low-pressure mater from the air-vessel. So long as the press-head is descending by gravity, high pressure is maintained, and the valve istherefore held open untilthe press-head comes torest upon the forging. When the press-head has come to rest the high pressure disappears, and all the valves, pipes andcylinders are only subject to the pressure in the air- receiver. The valve A, being no longer held up by the high pressure acting on itsannular surface, descends by gravity. The pumpsare started by means of t,he valve T, and continue pumping until the requisite amount of pressure is obtained. It isevident, however, that the press-head cannot be raised until the automatic valveA is opened. The closing of the pilot valve R is accompanied by the opening of the valve R, which relieves the pressure existing in the main-ram cylinders, and permits the valve A to be again lifted by the pressure in the annular space. The valve R being closed, the ascentof the press-head is effected by starting the pumping- engines in the same manner as for a compressing stroke. In order to effect all the motions of the press, the only lever which the attendant has towork is that shown at L, andthe pumping-engines are under perfect andinstantaneous control by means of the wheel M working the throttle-valve T bysuitsblc hunting gear. Plate 2. Tannett and Walker Forging-Press.-The first large press made by this firm vas of 4,000 tons power, for Messrs. John Brown and Company, of Sheffield. It is furnished with cranescapable of lifting 150 tons, and the engines for supplyingthe mater have cylinders 63 inches indiameter and 54 inches stroke.

Fig. 4 shows a 5,00040~press on asimilar plan to the above, which has been at work for some time in theworks of Mr. Fried. Krupp, at Essen. The top cross-head is movable with a rise and fallof 7 feet. The stroke of the main ram is 3 feet, SO that the total strokeof the press is 10 feet, and the arrangement is such that ingots 18 feet long can be pressed with this apparatus. The distance betweenthe columns is 18 feet. For locking orfastening thetop cross-head thereis an ingenious contrivance consisting of hydrauliccylinders and rams which move nutseither to liberate the cross-head and allow it to go up or down, or fix the said nuts, being somewhat similar to the action of a T-headed bolt which is put into its place and turned round; only in this case the nut turns.The anvil-block inthis press is also moved inand out by hydraulic pressure, and either an ordinary or a Bat anvil can be introduced at will by the simple movement of two hydraulic cylinders. Hydraulic cylinders raiseand lower the top cross-head. Thepumpingengines have 42-inch cylinders of 4Binch stroke, and the hydraulic accumulators are of the triple form; that is, with three rams, each ram 9 inches in diameter and 9 feet stroke, so arranged as to vary the power; that is to say, when working on the centre rams there is the full pressure, on the two outside rams there is two-thirds of the pressure, and when thepressure is turned on to all three thereis one-third of the pressure. The presses are situated in a building commanded by travelling cranes of 150 tons and 75 tons power, driven by square shafts, each with separate engines and two block-hooks to each travelling crane; one for lifting the full load, and the other for dealing with lighter loads,.and for working the porter-bar or turn- over gear. The span or distance from centre to centre of rails on which the travelling craneswork is about 60 feet. Fig. 5 shows a 2,000-ton hydraulic press, jn front and end view. This shows a press at work at theestablishment of theSociiti Cockerill, Seraing. The main ramhas a strokc of 6.3 feet. Thedistance between the columns is 12&feet, and the anvil block is moved in and out by hydraulic pressure as shown.

Plate 3. Greenwood and Batley Press.-This machine is a combination of the forging- press proper and a steam and hydraulic driving apparatus; the latter consists of a single-acting steam-cylinder, withpiston-rod a working in a smaller hydraulic cylinder. The press proper, Fig. 6, consists of a cast-steel hydraulic cylinder and cross-head (cast in one), connected by four columns to a cast-iron foundation-plate, having a planedsurface for theforging tools. The columns are prolonged above the hydraulic cylinder and cross-head, and carries a steam-cylinder, used for raisingthe cast-iron hydraulic,ram with the cross-head and tools. The steam supply for this raising cylinderis controlled by the regulator used for thc driving apparatus. The hydraulic forging cylinder is connected to the driving- cylinder without the intervention of any valves. On actuating the hand-lever of the regulator, the steam in theraising-cylinder is released, and the ramcross- head falls by its own weight and rests on the work to be stamped. A further movement of the lever, inthe same direction, admitssteam to the driving apparatus, and the full hydraulic pressure is applied. On moving the lever in a contrarydirection steam is admittedto the raising-cylinder,and theram cross-head (which is guided by the four columns) is quickly raised, the snper- kluous water in the hydraulic forging-cylinder is returned to the supply-tank. There is an automaticarrangement for keeping the maincylinder and pipes full of vater while the ramcross-head is being quickly lowered to the work.

Tweddell, Platt and Fielding System.-Fig. 7 shows a design for a 1,000-ton triple-power forging-press, the object of thearrangement being to allow as muchclear space as possible for the cranesand gear above the anvil. The aylinders are placed below the ground-level, and are arranged in a set of three. This not only keeps them of a manageable size and reasonable cost for very large presses, but admits of three powers being readily applied, thus effecting a greatsaving of pumping-power. Byfar the larger portion of the weight being below the floor-level, greatsteadiness is insured. A stationary base carries an anvil. In this base arearranged the cylinders, one or more with their rams projecting downwards and pressing on the low\er cross-head. This cross-head is connected to an upper cross-head by columns, which are guided through the base. The upper moving tool ordie is attached to the moving cross-head. Thereturn motion caube effected inany convenient manner. In the diagram it is shown done by rams. The cross-heads are at first allowed to fall by gravity (after having been raised in the first place by the lifting-rams), low-pressure waterfilling upthe space leftin the cylinders by the outgoing ram. Thenthe high pressure is applied for SO longas is desired. On opening the exhaust-valves the upper tool is again raised by the rams. Fig. 8 shms a 40-ton Press fitted with special quick-action valves, one of them has been for some time working in H.M. Dockyard, Keyham. There is nothing calling for special remark inthis press; but when practicable the Author prefers the type of press shown in Fig. 9. Of these a large number have been made, one of the first of them having been supplied to the French Government in 1883. They possess the advantage of permitting easy access to the dies and tothe work while it isbeing done. Severalleading railway companies use this type of machine, the largest amount of hydraulic stamping in this way probably being done at the Midland Railway Company’s wagon works, Derby, and at the North-Eastern Railway Works, Gateshead. Fig. 9, Plate 3, represents a 200-ton press of the class suppliedto the Great Western Railway Company, Swindon. With these presses, a great variety of work is done, including all the fittings requiredfor railway rolling-stock, also stamping the receiver-ends for air-brake vessels, and various details for loco- motiye engine forgings. In addition to the ordinary verticalpress-cylinder, this press has a horizontal ram at the back; also a supplementary ram in the bottom of the casting, the sides of which are planed and slotted in the same manner as ordinary drilling- or shaping-machines. The capacity and range of work of such a tool as this is very great.

NOTEBY MR. CHARLESDAVY, OF SHEFFIELD.

Without pretending to make an accurate comparison between a press and a hammer, few rough figures may serve to illustrate the contrast between the :WO. A hammer of 100,000 kilograms falling weight has a nominal travel of 5’00 metres, which is reduced to 3.50 metres if operating upon an ingot 1.50 metre thick. The work done in lifting the hammer is 100,000 X 3.50 = 350,000 kilogrammetres. The work or energy given out in arresting the descent is neces- snrily equal to thework done in lifting the hammer, assuming that thevelocity of descent has not been restricted by back-pressure in the steam-cylinder. The velocity of descent is, however, considerably retarded, part of the energy of the

falling mass beingexpended in forcing the exhaustout of the cylinder,in addition to theloss due tofriction. The amount of penetration effected, as represented by the distance traversed in arresting the descent of the hammer, is dependent on the superficial area of the hammer face, and on the hardness or softness of the ingot. For these calcu- lations it may be assumed to be 100 millimetres. It is possible to construct a diagram of the pressure exerted upon the ingot by the falling weight, hori- zontallines representing pressures and vertical lines representing space travelled during the retardation. Under the most favourable, but really unat- tainable conditions, the diagram is known to have an area representing350,000 kilogrammetres of work. The travel being 0.10 metre, it follows that theforging must offer an average resistance of 3,500,000 kilograms, but the falling weight may be capable of exerting a pressure of 7,000,000 kilograms ou its first contact with the forging. The whole operation of bringingthe falling parts to rest occupies so little time thatit is impossible that thepressure of the blow can be felt equally and uniformly through the metal. A press dynamically equivalent to the above hammer would be capable of exerting a constant pressure of 3,500,000 kilograms, and the diagram of energy would be a simple rectangle. The time required to effect the compression would be several seconds. As the hammer cannot develop the full amount of energy stored in raising the tup, it is certain that a press of less than 3,500 tonnes power would be equivalent to a 100-tonne hammer.

EXPERIMENTSBY &fR. COLEMAN SELLERS OX BILLETSOF LEADCAST FROM THE SAME PIG,SHOWING THE EFFECT OF A NUMBER OF HAMMER-BLOWS,AND THE PRESSUREREQUIRED IN A HYDRAULICPRESS TO DEFORMSIMILAR TEST-PIECES TO AN EQUAL EXTENT.

Ezperiments with a Steam-Hammer on Billets of Lend.

Diameter, 3 inches ; length, 3& inches ; weight, 3 Ibs. ; contents, 30.73 cubic inches.

No. of Leugth of Mean Diameter Stroke of Inch-Lbs. Pressure per Blows. Billet. Billet. 1 Blllet. 1 of 1 Hammer. 1 Developed. 1 Inch Of Inches. Inches. Inches. Lbs. 1 2 3.64 19 156,180 20,553 2 18 4.38 298 161,317 20,792 3 It 5.22 202% 164,660 20,792 4 B 5.93 206 166,455 31,501 5 Q 6.50 20" 167,482 44,362

Stevens Institute of Technology, vol. vi. p. 9.

Compression of similar Billets in a mheeLPress, to show the Action of Hydraulic Pressure in producing the sameDeformation a8each Hammer-Blow h& produced.

Length of Blllet. ------Inches. Square Inches. Lbs. ~~c~~areLbs. Inches. Lbs. 2 10.8 1,000 63,617 3.71 15.71 I 4’47 6,4155,890 18 1,600 101,787 I 1 21.6 2,500 150,042 5-25 I 7,383 28.8 6’06 2 4,100 260,330 , 6,056 8 34.56 5,000 318,085 6.63 9,200 l

The above tabulated resalts show the calculated force of the blows worked out on data obtained by other experiments; and the power is expressed in inch-lbs., as well as the pressures per square inch on the billet at the end of the blows. These figures cannot be absolutely correct, but they arequite within the bounds of truth,and allowance has been made for errors. It will be noted that it took five blows to reduce the billet to the final thick- ness of f; inch; when the last blow was over 20 inches long the inch-lbs. developed were 167,382, and the pressure per square inch on the billet was 44,362 lbs. Under the press it was possible to produce the same amount of com-

pression, or L‘ deformation,” as it was called, by one continuous operation. The operation, which might have been continuous,however, was interrupted at intervals to note the pressure at the periods equivalent to the result of each hammer-blow. As the billet extended and presented greater area to the plunger or ram of the press, and the disk of metal became thinner, the pressure required increased on account of the frictional resistance being greater in the thin disk. In no case, however, does the pressure per square inch on the billet reach one- third of the calculated result of the hammer-blows. This experiment confirmed what was understood to be the ease, that it certainly takes less than one-third of the pressure to forge by compression between dies of that which is required under the steam-hammer. This was also confirmed by some experiments made with closed dies, like moulds, in which hot steel and iron were submitted to pressure to cause it to fill the mould. It %as found that 6,000 lbs. per square inch caused the metal to flow and almost fill the mould, but that a pressure of nearly 16,000 lbs. per square inch was necessary to completely fill the sharp corners of the mould.

I+ l

ETLy S1 _.

DAVY 2000 TONS PRESS.

Eii;ps: 9

500 TONS PRESS