292 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



LSeptembeh, 



flat- 



FlB. 1. 



IRON FORGING. 



Improvements in Forging Iron. By James Nasmyth. 

 Befor?: proceedings to describe the nature of the improvements 

 in question, iMr. Nasmyth made some remarks on the value and 

 importance of any improvement which tended to increase the cer- 

 tainty of the production of sound and perfertlv solid forgings of 

 wrought-iron, more especially those massive forjfings required for 

 such jiurposes as jiaddle-shafts, marine engines, crank and plain 

 axles for locomotive engines, anchors, and such like, on the sound- 

 ness of which both life and pnqjcrty to a vast amount may depend. 

 Mr. Nasmyth instanced cases in which paddle-shafts of marine 

 engines had given way, although in the first instance thev had all 

 the ou^tYn-rf aspect of the most perfect soundness, but which on 

 fracture exhibited the existence of original defect, in being little 

 else internally than a mass or bundle of loose bars of iron, which 

 had never been in a sound welded union, but had onlv been held 

 together by the exterior, where alone the welding had 'been so far 

 perfect. 



Mr. Nasmyth exhibited a diagram of which fig. 1 is a copy, in 

 order to illustrate the action induced on the centre portion of 

 a cylindrical forging, when i)roduced under the action of 

 laced hammer and anvil. 



It will be seen at once that the 

 action inducedonthe centre portion 

 of the metal of a shaft, or such like 

 cylindrical form, by the successive 

 blows of a flat-faced hammer and 

 anvil, as a and b is to cause the 

 work to spread out or extend in the 

 direction e d, e c (as rei)resented by 

 the double pointed arrow on tlie fi- 

 gure); and as the flattened-out form 

 has to be attempted to be corrected 

 by turning the shaft round and 

 round on the anvil, so tlnit each 

 .successive blow may be made to 

 correct the spi-eading out caused 

 by the previous blow. The result 

 of this action is a fretting or mincing 

 of the centre part of the metal of the shaft, 

 resulting in a separation of the metal 

 throughout the entire centre portion of the 

 shaft, somewhat after the manner indicated 

 in fig. 2, frequently to such an extent as to 

 permit the passage of air or water from end 

 to end of shafts forged in this manner. 



The effect of this kind of unsoundness is 

 that it is certain, sooner or later, to workout 

 towards the exterior, and in all probability result in "a break 

 down more or less disastrous in its consequences. 



iMr. Nasmytli then proceeded to describe his improved form of 

 anvil-.'ace, by the employment of which all such defects as detailed 

 above are avoided. Such has been the perfect success and excel- 

 lent results which have attended the use of his improved anvil- 

 tace, that its adoption has become almost universal; and the pro- 

 duction of absolutely sound solid wrought-iron shafts, of whatso- 

 ever magnitude, rendered enuully easy as certain. 



A, (fig. 3) re- 

 presents the form 

 of Mr. Nasmyth's 

 improved anvil- 

 face, which he 

 terms a V-anvil, 

 between the jaws 

 of which the work 

 to be hammered 

 is placed as indi- 

 cated by a cylin- 

 drical shaft, seen 

 in section marked 

 cc c. 



A glance at the 

 above figure will, 

 no doubt, render 

 its action evident, 

 namely, that the 

 action of each blovy 

 of the hammer on Fig. 3. 



the work c c c, instead of causing, as in tlie case of fig. l,a di- 



verging action on the centre portion of the work, occasions on the 

 contrary, a converging action, as represented by the three arrows • 

 and instead of having the centre portion of the metal of the shaft 

 renilered less compact and solid by the action of the blows of the 

 hauiincr, we have quite the contrary effect produced ; l)esides wliich 

 owing to the wedge-like form and action of this V-anvil face the 

 compressing effect of the blows are most importantly enhanced 

 and the ease and rapidity with which sucli cylindrical-formed 

 work as shafts and the like can be produced under or by such 

 means is most remarkable; so much so as to enable the forgemen 

 to hammer out at one heat, by means of this A'-aiivil, as much as 

 would require three heats on the common flat-face anvil. Add to 

 which the vast convenience which the fork-like form of the V anvil 

 yields in keeping the work at all times right under the centre of 

 the hammer, as it is turned round and round to receive the succes- 

 sive blows, which in the case of work of the largest class is a matter 

 of no small trouble; another advantage consists in the free passage 

 or exit which is at all times preserved for the escape of the scales 

 and impurities which fall from the hot iron during the process of 

 hammering, which scales fall down towards the apex of the Vat 

 D, and trickle away, thus removing the cause of blemish and rough- 

 ness which is caused by such scales collecting on the face of the 

 flat anvil, and get beat into tlie surface of the forging. 



it will be seen on inspecting fig. 3, that one such V-anvil face 

 as there represented, will accomodate a vast range of diameters of 

 namely, all variety of diameters, such as will neither abso- 



work- 



lutely rest on the bottom of the apex at d, or on the corners p f. 

 Mr. Nasmyth has taken every means, by the most free commu- 

 nication, to promulgate among those interested the advantages of 

 this \ -anvil, and has been rewarded by seeing its use become 

 almost universal. 



iMr. N. stated that an angle of 80° was found by him to be most 

 generally suitable for the inclination of the sides of the V, and also 

 that the edges should be well rounded off, and the surface of the 

 V sides curved in the direction of the axis of the work, to the 

 extent of gth of an inch in 12 inches, so as to be '■^ proud" in the 

 centre, and so facilitate the extension (axis ways) of the work. 

 The vast simplicity, as well as the important results, which are 

 yielded by the employment of this V-anvil face, has, in no small 

 degree, contributed to its almost universal adoption. Its em- 

 ployment renders the production of perfect sound work as easy 

 as certain. 



Mr. Nasmyth next proceeded to describe the second part of his 

 improvements in forging iron, which consist as in the first case, of 

 means equally certain and simple in producing sound boiler plates. 

 .Air Nasmyth prefaced his description of his improvements on this 

 truly important subject by detailing the nature of the most fre- 

 quent cause of unsoundness in iron forgings generally, and in 

 boiler plates in particular, namely, the imperfect expulsion of the 

 molten oxyd of iron, or " scoria," or " cinder," as it is termed, 

 which in every case of welding hot iron covers and clings to the 

 surface of the metal; and if left interposing between the welded 

 surfaces, is certain to occasion a defect greater or less according to 

 the surface of junction it occupies. The frequency of this interpos- 

 ing scoria as the true cau.ie of unsound forged work was forcibly 

 alluded to by Mr. Nasmyth, and shown to be the most fertile 

 source and cause of the failure of wrought-iron work, resulting as 

 such too frequently does, in the most sad and disastrous accidents, 

 such as the failure of the links of chains and anchors, and in the 

 costly and often distressing results arising from defective, i. e. blis- 

 tered boiler plates. 



In respect to the links of chains, Mr. Nasmyth mentioned as the 

 result of an extensive series of experiments on the strength of 

 chain cables, on which, as member of "the committee on metals,' 

 he was employed by the Admiralty; out of every ten cases of frac- 

 ture, eight were occasionid by defective welding, as evinced by the 

 appearance of the surfaces, which present to a practical eye 

 appearances not to be mistaken, owing to the very peculiar 

 aspect of the surface of the apparently welded metal, between 

 which surfaces the oxyd or scoria had not been duly expressed. 



Mr. Nasmyth further described the condition absolutely requi- 

 site to perfect welding, namely, not merely tliat the surfaces we 

 desire to weld should be really " welding hot," but also that when 

 brought into contact, no particle of the scori.i, which inevitably 

 clings to the metal while welding hot, should be jiermitted to 

 remain interposing between such surfaces as we desire to weld. 

 If such material is left interposing, we are certain to have defect 

 and unsoundness to a greater or less extent as the result. 



In order the more clearly to detail his improvements on this 

 important subject, Mr. Nasmyth exhibited a coloured drawing 



