ROLLING-MILL. 



Rollers are ufually made of caft-iron, and are very exaftly 

 turned on their 1'urfaces, and alto the.r necks, that they 

 may turn truly when put in their places. The moil common 

 way of turning themh, firll to mount the roller in a ilrong 

 turning lathe, bv holes or centre points made in its ends; 

 then to turn the two necks truly cylindrical ; and afterwards 

 putting the roller in its proper place in the roller. frame, and 

 placing brall'cs over (he necks, they are held down by 

 blocks! fitted under the pieces which retain the gudgeons oi 

 the upperroller : in this fituation it is put m motion by the 

 mill, and a bar of iron being fixed up for a reft, the furface 

 of the roll is turned true, in the fame manner as it it was in a 

 lathe, and will be certain to be exaft, being formed from the 

 fame necks on which it is afterwards to work. In caftmg 

 a roller, the mould fhould always be placed at a confiderable 

 depth beneath the orifice where the metal is poured m, lo 

 that the preffure of a column of the fluid metal may be ob- 

 tained to confolidate the calling, and render it free from thole 

 air-holes, or porous places, which will fometimes occur in 

 metals call without the preflure of a column The long 

 piece of Hiatal which filled the aperture through which the 

 metal ran, is left adhering to the roller, and is cut oil af- 

 terwards. This is the fame mode of calling that is prac- 

 tiled for cannon (fee that article). Cafe-hardened rollers 

 mull be ufed when it is required to have a very tair lur- 

 face; w. forfuch purpofes as roll.ng iron to make thin plates 

 for tinning ; alio the large rollers for gold or Giver, fuch as 

 are now ufed in the Royal Mint ; rollers for making tin-foil, 

 fteel-plate for faws, and for many other purpofes. 1 hefe 

 rollers are not hardened by a fubiequent procefs, as in cale- 

 hardening wrought iron, but are call in that Hate. I his is 

 eifeded by employing iron moulds : a call-iron cylinder oi 

 three inches thick, and its diameter equal to that oi the 

 roller, is bored out with great accuracy, and fitted with 

 ends proper to form moulds for the necks required at each 

 end of the roller ; this is buried in the land of the foundry, 

 and when the metal is run into it, the rapid trarifmiffion of the 

 heat through the iron mould caufes the metal which is in 

 contaft with it to cool fooner than the other parts of the 

 mafe, and renders the furface of the roller very hard. In 

 turning a roller of this kind, the centres mull be chofen lo 

 that the circumference turns as true as it will admit, and 

 then a very fmall quantity being taken oft, will render 

 ,t perf-d : this care fhould be taken for two reafons ; 

 firft, that lefs will be required to be removed to make it true, 

 which is a difficult operation, as only the bell flee tools will 

 cut it ; alio, that if the metal is unequally reduced, or more 

 on one fide than the other, the hardelt part will there be 

 cut away, and the roller will have a hard and a iott fide, 

 and foon wear out of the circular figure, and require a fc- 

 cond turning. The lefs metal there is turned oil a cale- 

 hardened roller the better it will be, bccaule the hard part 

 is only a cafe of flight thicknels, and moll hard at the 



furface. .„ . r ,. . r , 



The operation of the rolling-mill is fo fimple, as fcarcely 

 to require a H y defcription : the metal is heated in rever- 

 berating furnaces when it is in large maffes, and for malic- 

 es a kind of oven is ufed, in winch the cokes are laid on 

 the bottom or floor of the oven without any grate-bars, and 

 therefore the draft of air being lefs rapid, it gives a (light, 

 but very regular heat, which rifes to a bright red, but no 

 farther, and therefore it does not wafte the iron by burning 

 it to fcales, as a greater heat and current of air will do. 

 This oven is proper for heating plates, hoops, or fmall b « 

 to be rolled a fecond and third time : but for rolling large 

 maffes, a ftro,g welding heat is reqmfite, that the metal may 

 ■oniohdated, and all flaws or cracks fecurely clofed. The 



reverberating furnace is ufed for this purpofe ; it is made 

 the fiime as an air-furnace for melting large quantities of 

 iron, except that the floor is horizontal ; indeed it is as near 

 as poilible fimilar to the balling furnace. (See Plate II. 

 Iron Manufacture. ) The furnaces are placed as near as 

 convenient to the rollers. 



The iron, being heated in the furnace to the proper degree 

 for the purpofe which is intended, is taken out by a pair of 

 pincers, the mill put in motion by drawing the fhuttle, and 

 the iron is prefented to the rollers, which are previously ad- 

 julted to the thkknefs of the piece which is to be palled. 

 If this is not attended to, and the workmen attempt 

 to reduce the iron too much at one time, there is danger of 

 breaking fome of the machinery, or of itopping the mill 

 whilit the iron is only half palled through : this is a dif- 

 agreeable accident, as it will require four or five men, with an 

 enormous wrench applied to the nuts of the roller, to turn 

 them back fufficiently to relieve the rollers, fo forcibly are 

 the fcrews prefled whilit the iron is pafling through : this is 

 indeed evinced by the circumitance of folid eait-iron rollers, 

 of ten inches in diameter, being fometimes broken in the 

 middle ; and the necks of eight and nine inches are frequently 

 fnapped. When the iron is placed on the fhelf or table before 

 them, their motion will draw it through, and as they cannot 

 recede from each other, becaufe of the nuts of the bolts, 

 the metal is reduced to the exadt thicknefs of the fpace be- 

 tween them, increasing in length, but not at, all in breadth : 

 the iron is caught by another workman behind the rollers, 

 and returned over the top roller to the firft man, who puts it 

 through again, firft giving the handles of the nuts a fmall 

 turn, to bring the rolls nearer together. In this manner it 

 is repeatedly rolled, till it is reduced to any required length 

 and thicknefs, but the breadth is not at all increafed by 

 rolling ; and if it is required to incrcafe the breadth, it is done 

 by putting the iron obliquely through the rollers ; or if a 

 great increafe is wanted, the iron is put through breadth- 

 wire two or three times, till it is extended to the length of a 

 gauge which the workman has marked upon the table in 

 front. 



Rolling of black Plate, fuch as is ufed for making the 

 boilers of fteam-engines, tanks, or other large veffels, in 

 wrought iron. Such plates, when large, and of confiderable 

 thicknefs, are rolled from the blooms, or half blooms, which 

 are made under the forge-hammer. Thcfe blooms, which 

 are alfo called flabs, are nearly the length of the intended 

 plate ; their breadth about one-half or one-third as much as 

 their length, and of a thicknefs to contain as much metal as 

 will make two, three, or four plates. Thcfe pieces, when 

 heated to a white heat, are prefented breadthwife to the 

 rollers, and pafled through feveral times at the rame heat, 

 until what was the breadth of the bloom, being extended 

 two or three times as great, becomes equal to its length. The 

 thick fquare plate, thus formed, is now cut up by the (hears 

 acrofs into two or three pieces, of about the fame fize as t he 

 firll, but in a direction which will make what was the length 

 of the firll piece to be the breadth of the fecond. T 

 pieces, being heated and rolled again, becora ■ extended to the 

 fize of the required plates : the reafon of thus dividing the 

 operation is, that the rolling only extends the metal in the 

 direction in which it moves, and not at all in breadth : by 

 this means, the particles of iron being drawn by the fid 

 one another, acquire fomething of a fibrOU8 texture, or an 



approach thereto, which is defirable in bars, rods, and 

 hoops, hut not at all m plate, as u Ihould be equally Ilrong 

 in either direction j tb refore, by rolling it firft one way, and 

 then the other, the grain, as far as it is produced at all, is in 

 both directions. There is no doubt that better plate would 



be 



