COINING MACHINERY. 



723 



Circular 

 heats. 

 PLATI 

 CCI. 

 Fig. 4. 



Coiniug plete rolling mill we have ever seen, and the workmanship 

 Machinery. o fitis unrivalled: It was executed by the celebrated en- 



~~Y~~ gineer John Rennie, Esq. 



Operation The ingots of silver are heated to redness in a furnace 

 /rolling, before they are rolled. The two furnaces for this purpose 

 are situated before two pair of rollers, which are there- 

 fore termed breaking down rollers, being used to consoli- 

 date the metal by rolling whilst hot. In the operation, 

 two men are employed ; one takes the metal from 

 the furnace by a pair of tongs, and introduces it be- 

 tween the rollers ; the other catches it as it comes 

 through, and lifting it over the top roller, returns it to the 

 first, who puts it through again, having previously turn- 

 ed the handle S a small quantity, to set the rollers near- 

 er together. After having been rolled in this manner four 

 or five times, they are reduced to near two-tenths of an 

 inch in thickness, and increased in length to about four 

 times the breadth of the ingot j for it should be observed, 

 that the ingots are roiled across their breadth, the longeit 

 tide being presented to the rollers ; and as the rollers 

 do not extend the plate sidewise, the plates, when finish- 

 ed, are as broad as the length of the ingots, viz. 10 inches, 

 and three or four times as long as the- breadth of the ingot, 

 i. e. from 21 to 28 inches. These plates, whilst still warm, 

 are rubbed over with a weak solution of acid or pickle, 

 to remove the colour produced by the heat, and are then 

 cut up into narrow slips across the breadth of the plate, 

 by means of the circular shears, Fig. 4. Plate CCI. This 

 machine is worked by a cog wheel at the extremity of 

 the main shaft B, Fig. (i. of the rolling mill. It con- 

 biats of a framing of iron A A, supporting two shafts BB, 

 which are parallel to each other, and move together by 

 means of two equal cog wheels CC, the lower one of which 

 works with the teeth of the great wheel above mention- 

 ed, upon the main shaft of the rolling mill. At the ex- 

 tremities of the two shafts, whet-Is or circular cutters are 

 fixed, their edges overlapping each other a small quanti- 

 Fig. 5. ty, gg is shewn in the edge view Fig. 5. Here it is seen 

 that each cutter has a rim of smaller diameter than the 

 outside : this small rim in the top cutter is behind it at 

 e, but is in front of the lower ot-.e at g, so that the ad- 

 jacent edges of the large nmsyand k come in contact, 

 and overlap each other a small quantity. By this means 

 they act in the same manner as shears, to cut any thing, 

 as c, (I, which is interposed between them, by depressing 

 one half d, and elevating the other c, til! they are com- 

 fig. 4. pletely separated. F, Fig. 4, represents a shelf on 

 which the plate is laid, and advauced forwards to present 

 it to the cutter ; and G is a ledge or guide, screwed down 

 upon it, to guide the metal, and, by its distance behind 

 the planes of the cutten, to regulate the breadth of the 

 piece which shall be cut off ; for this purpose the screws 

 which fasten down the ledge are fitted in oblong holes, 

 which admit of small adjustment. The workman holds 

 the plate flat down upon the surface F, and advancing 

 it towards the shears, they will continue to draw it 

 through, when they once takr hold, until they have cut 

 the whole length, c d, Fig. 5. shews a section of the 

 plate to explain the manner in which it is cut : The part 

 c is conveyed upon the top of the rim k of the lower 

 cutter, and kept down from rising by the small diame- 

 ter e of the upper cutter ; at the same time, the other 

 part of the plate is depressed by the rim /"of the up- 

 per cutter, and supported by the small rim g of the low- 

 er one. By this means, the divided parts c and il are pre- 

 vented from curling up into scrolls, as they will, when 

 cut in a common pair of shears, because the small parts 

 e and g keep them straight. Behind the standard, sup- 

 porting the back pivots of the shafts BB of the cutter, 



is a frame /, with a screw m tapped through it. This is Coining 

 used to draw the axis of the upper cutter D endwise, R1 

 and keep its edge in close contact with the edge of the """Y"" 1 

 other cutter E. The slips of plate are now carried to 

 the other two pair of rollers in the rolling mill, which 

 are made of case-hardened iron, and with a better polish on 

 their surface than the breaking down rollers. The plates 

 are passed cold between these, to bring them exactly to 

 the requisite thickness ; hence they are called the ad- 

 justing or planishing rollers. The workman here tries PLATE CC. 

 every piece as it comes through by the gauge Fig. 8. Fig. 8. 

 This is a piece of steel, having a notch in it, the inside 

 lines of which are very straight, and inclined to each 

 other at a very acute angle. They are divided, as is shewn 

 in the Figure, so that the edge of the plate being pressed 

 into the notch, will have its exact thickness determined 

 by the distance it will go into it, the divisions shewing 

 the dimensions in parts of an inch. 



In rolling the plate the second time, they pass all the 

 slips successively through the rollers, then adjust the 

 rollers by the handle, and pass them all through a second 

 time. This is repeated three or four times, and the last 

 time they are every one tried by the gauge, and sorted 

 by it into as many parcels as they find different thick- 

 nesses ; for it is a curious fact, that though the rollers 

 are 14; inches in diameter, and the frame proportionally 

 strong, still they will yield, in some degree, so as to re- 

 duce a thick plate in a less degree than a thin one ; and 

 the plates which have all passed through the same rollers 

 will be of three or four different thicknesses, which be- 

 ing sorted by the gauge into as many parcels, they be- 

 gin to reduce them to the exact quantity, by setting the 

 roller according to each parcel : then the first of the par- 

 cel which comes through is tried, by cutting out a cir- 

 cular piece with a small hand machine, Fig. 6. Plate CCI. Pt ._ /,, 



1 _ i i Tf ! l i * "ATE vl^if 



and weighing it: ir it proves too light or too heavy, the Fig. 6. 

 rollers are adjusted accordingly, till, by a few trials, they 

 are got right, and then all the parcel is rolled through. 

 The next parcel is then tried, and so on ; the trial plates 

 which are too thin being returned as waste to the melting 

 house. By these precautions, the blanks when cut out 

 by the next machine will be very nearly all the same 

 weight, which they would scarcely be even if the gauge 

 determined all the plates to the same thickness, because 

 some being more condensed than others, they could not 

 all have the same specific gravity. 



The cutting out machine is explained by Figures 1,2, Cuttingout 

 and 3, Plate CCI. or at least sufficient is there shewn to machine. 

 describe the whole. A A is a basement of stone to sup- PLATK CCI. 

 port an iron plate B B. On this, columns C C are erected to F 'S S ' > 2 > 

 sustain the upper part D of the frame. The iron frame of aml 3 " 

 the machine, marked EEF, is fixed down upon the 

 iron plate B : it has a screw a fitted through the upper 

 part, which acts upon a slider l>, supported by a cross 

 bar c of the frame : it is cylindrical, but has a leaf or fillet 

 on the front side, to prevent it from turning round. The 

 punch d is fixed in the lower end of it, and immediately 

 beneath it is the die or bed e, which is adjustible, by 

 screws, to its true position. These parts are very nearly 

 the same as the original cutting out machine ; but the 

 manner of actuating it, by the power of a steam en- 

 gine, instead of hand labour, constitutes the improve- 

 ment. Above the screw is an axis G, fitted on the top * 

 of the screw, with a socket, and the upper end sup- 

 ported by the frame D : above this support, a lever 

 N H is fixed to the axis, to receive the action of cams or 

 wipers fixed on a large horizontal wheel, situated be- 

 hind the machine. This wheel is shewn in Fig. 2, in which Fig. 2. 

 KK is a plan of part of its rim, and L one of its cams. 



