IRON 1017 



accurately worked together. The decrement in the capacity of the grooves follows the 

 proportion of 15 to 11. 



When it is intended to reduce the iron to a small rod, the cylinders have such a dia- 

 meter, that three may be set in the same housing frame. The lower and middle 

 cylinders are employed as roughing rollers, while the upper and middle ones are made 

 to draw out the rod. When a rod or bar is to be drawn with a channel or gutter in its 

 face, the grooves of the rollers are suitably formed. 



To draw out square rods of a very small size, as nail- 1281 



rods, a system of small rollers is employed, called 

 slitters. Their ridges are sharp-edged, and enter into 

 the opposite grooves 2 inches deep ; so that the flat bar 

 in passing between, such rollers is instantaneously 

 divided into several slips. For this purpose the rollers 

 represented in fig. 1281, may be put on and removed 

 from the shaft at pleasure. 



The velocity of the cinders varies with their dimen- [/* I -^>^ J 



sions. In one work, cylinders for drawing out iron of 



from one-third to two-thirds of an inch thick, make 140 revolutions per minute ; while 

 those for iron of from two-thirds of an inch to 3 inches, make only 65. In another 

 work, the cylinders for two-inch iron, make 95 revolutions per minute ; those for iron 

 from two-thirds of an inch to an inch and a third, make 128 ; and those for bars from 

 one-third to two-thirds of an inch, 150. The roughing rollers move with only one- 

 third the velocity of the drawing cylinders. 



The shingling and plate-rolling mill is represented in fig. 1280. The shingling mill, 

 for converting the blooms from the balling furnace into bars, consists of two sets of 

 grooved cylinders, the first being called puddling rolls or roughing rolls ; the second 

 are for reducing or drawing the iron into mill-bars, and are called simply rolls. 



a, a, a, a, are the powerful uprights or standards called housing frames, of cast iron, 

 in which the gudgeons of the rolls are set to revolve ; b, b, b, b, are bolt rods for bind- 

 ing these frames together at top and bottom; c, are the roughing rolls, having each a 

 series of triangular grooves, such that between those of the upper and under cylinders, 

 rectangular concavities are formed in the circumference with slightly sloping sides. 

 The end groove to the right of c, should be channelled like a rough file, in order to 

 take the better hold of the blooms, or to bite the metal as the workmen say ; and give 

 it the preparatory elongation for entering into and passing through the remaining 

 grooves till it comes to the square ones, where it becomes a mill-bar, d, d, are the 

 smooth cylinders, hardened upon the surface, or chilled, as it is called, by being cast in 

 iron moulds for rolling iron into plates or hoops, e, e, e, e, are strong screws with 

 rectangular threads, which work by means of a wrench or key, into the nuts e' e f e' e*, 

 fixed in the standards ; they serve to regulate the height of the plummer blocks or 

 bearers of the gudgeons, and thereby the distance between the upper and under 

 cylinders, /is a junction shaft; g, g, g, are solid coupling boxes, which embrace the 

 two separate ends of the shafts, and make them turn together, h, h, are junction 

 pinions, whereby motion is communicated from the driving shaft /, through the 

 under pinion to the Tipper one, and thus to both tipper and under rolls at once. i, i, 

 are the pinion standards in which their shafts run ; they are smaller than the up- 

 rights of the rolls, k, k, are screws for fastening the head pieces I to the top of the 

 pinion standards. All the standards are provided with sole plates m, whereby they are 

 screwed to the foundation beams n of wood, or preferably iron, as shown by the 

 dotted lines ; o, o, are the binding screw bolts. Each pair of rolls at work is kept 

 cool by a small stream of water let down upon it from a pipe and stop-cock. 



In the cylinder drawing, the workman who holds the ball in tongs passes it into 

 the first of the elliptical grooves, and a second workman, on the other side of the 

 cylinders, receives this lump and hands it over to the first, who repasses it between 

 the rollers after bringing them somewhat closer to each other by giving a turn to the 

 adjusting pressure screws. After the lump has passed five or six times through the 

 same groove it has got an elliptical form, and is called in England a bloom. It is next 

 passed through a second groove of less size, which stretches the iron bar. In this 

 state it is subjected to a second pair of cylinders, by which the iron is drawn into 

 flat bars four inches broad and half an inch thick. Fragments of the ball or bloom 

 fall round about the cylinders, which are afterwards added to the puddling charge. 

 In a minute and a half the rude lump is transformed into bars with a neatness and 

 rapidity which the inexperienced eye can hardly follow. A steam-engine of thirty 

 horse-power can rough down in a week 200 tons of coarse iron. 



This iron, called mill-bar iron, is however of too inferior a quality to be employed 

 in any machinery, and it is subjected to another operation, which consists in welding 

 several pieces together, and working them into a mass of the desired quality. The 



