Fig. 258 shows a level floor of heavy cast-iron slabs used for bending angles and other structural shapes to various curved forms for ship frames. The slabs are well supported on permanent foundations, and the regularly spaced square holes in them are used to hold various pins and eccentric washers against which the frame is bent.

To arrange for bending, a wooden template giving the required curve of the frame is placed on the slabs and the curve is marked thereon with chalk. Pegs and washers are placed in the square holes along the chalk mark as guides against which the frame is to be bent. An angle bar or other long piece to be bent is heated to a red heat in the long furnace shown in the background. The view shows the workmen in the act of dragging an angle from the furnace. This is dragged out, one end is secured between two pegs at one end of the curve outlined on the slabs, and the other end is dragged by suitable bars and other appliances against the guide pins and there clamped until cold. Very convenient clamps or dogs for this use consist of heavy round bars of iron bent into a flattened

Fig. 258. - Bending Slab and Heating Furnace.

V-shape, i. e., with the two legs slightly less than 90° to each other. One leg is set in a slab hole and as the other comes against the work, a stroke of the hammer sets it tightly in a leaning position in the hole.