After the plates are drilled they are marked for lap by using the butt strip template at each end, thus: - The template is laid on and steadying pins put through the holes, the ends marked with a scriber, and then either a long straight-edge and scriber, or a chalk line is used, the plates having been drilled as far as possible to admit of shearing on two edges only, one side and one end. At the same time, the second barrel plate is marked for punching out the dome bole, which is not removed until after the plate has been bent, being held from four opposite points; and the third barrel-plate is marked for punching the clearance for the saddle or throat-plate, which is removed entirely before bending. The plates are then sheared and punched, leaving ⅛ inch or 3/16 inch for the planing machine. In all boiler shops there are plate edge planing machines to plane edges from 10 to 20 feet, some with turnover tool boxes, some with quick return; the former should be used wherever possible, because of the great saving of time, not to mention wearing the back edge of the tool, for there are very few side planers fitted with spring boxes to lift the tool completely away from the work upon the quick return. Others are provided with the vertical lathe arrangement, and finally, the plate edge and butt planing machine. When planing the ⅛ inch or 3/16 inch from the edges of the plates, the tool is ground to an angle of about one in eight, and the edge of the plate must have the inclination of this angle, according to its eventual position, to suit the fullering; that is, the inside lap is planed to the opposite inclination of the outside lap, clearly shown in Figs. 1-4 and 11-13.

The shell plates are next taken to the rolls and bent to diameter, the operation simply consisting of putting the plates through a set of three cast-iron rolls from 12 inches to 18 inches diameter, and rotating backwards and forwards, screwing the top or aide roll, as the case may be, up or down, until the plates acquire the desired radius. This method, however, leaves about 4 or 5 inches at each end straight, which has to be set afterwards, generally either by making a casting, or setting a stiff plate to the required radius; then heating up the shell, dropping it into the "former," and striking a few blows with a medium heavy hammer. The method of getting the shell out from this machine, Fig. 7, is rather cumbersome: the top roll is raised up clear of the shell and wedged at one end, while at the opposite end the housing is removed and the plate drawn out. Another and a very convenient plate-bending machine, Figs. 8, 9, has the centre of the top roll in the same plane as the bottom one, the third roll being placed at the side, which is the adjustable one. This machine bends the plate to the very edge at one end, and by a very simple arrangement, shown in Fig. 8, the plate can be taken out, turned round, and the other end bent, so that the shell does not require any setting in blocks; this being the method used in bending the plates for the boiler in question.

The bearing at A, Fig. 8, can be withdrawn as indicated, and then the roll swivels round upon a kind of ball-and-socket bearing at B, counterpoised by the roller and its path C. Care must he taken to enter the plates square, which is easily done by running the eye along the edge of the plate, or a line of rivet holes, and the top roll. This is especially necessary in the case of dome plates, as owing to their short circumference and stiffness they will not spring so much as a barrel plate. The plates are rolled almost exactly to radius, but sometimes, owing to little irregularities, such as hard places, buckle, etc, they need a little setting afterwards, which is easily accomplished by two or three blows with the hammer. At the same time the inside and outside butt strips are dealt with, being drilled through a template in the same manner as the barrel plates, in batches of five. They are countersunk about ⅛ inch deep, and all burrs removed, then marked for shearing, being sheared from the side next the barrel plate, so that the bevel edge comes next the shell for fullering. They are not planed, because the shear blades are kept in good order, and being small plates, the workman has perfect command over them, consequently the shearing is a good finish; they are then bent to the radius of the shell. The dome strengthening plates are drilled through a template, marked for shearing and punching, and then bent; these also in batches of five, and with the same template system as the barrel plates. The continuous weldless ring of mild steel, from 28 to 30 tons per square inch tenacity, and 20 per cent, elongation on 8 inches, Fig. 1, for securing the smoke-box tube plate to the first shell plate, is faced, bored and turned to section, slightly heated, and shrunk on to the first barrel plate. This ring is drilled through the barrel plate from the inside, which acts as a jacket, by a specially designed drilling machine, using the opposite side to resist the thrust of the drill; or at a specially designed flange drilling machine. After the ring has been riveted to the first barrel shell, the three shells, straps and dome strengthening plate are all bolted together and riveted at one operation, Fig. 10, and it has been found that the riveting up of these two joints elongates the barrel 3/32 inch, and allowance is made accordingly.