There is also an hydraulic stamping press for bending angles and tees to form knee-bars and other stiffening pieces, the cylinders being 14 in. in diameter, working at a pressure of 800 lb. per square inch, with a stroke of 18 in. The machine, which has been constructed by Sir William Arrol and Company, Limited, consists of an hydraulic cylinder mounted horizontally on a massive table. On the ram-head there are former blocks, while on the table in front there are corresponding dies. The bar is placed on the table between the blocks and dies, and as these are forced together by hydraulic pressure, the bar between them is squeezed into the exact shape required. Not only is the operation expeditiously executed, but there is no uncertainty. The whole of the metal within the bar is retained inside the knee, which becomes thicker and broader, materially adding to its strength. As the moulds or dies can be made to suit any form, the machine can be utilised in the preparation of various details of structures, provided they are designed with a view to their production by aid of dies. The great economy resulting from the use of special machines is only realised when the designing staff remember that they must be kept employed.

A specially powerful tool is provided for bending channel irons and beams, and for drilling horizontal holes in them. Hydraulic manhole-punching and flanging machines are employed, each having a ram of 27 in. in diameter, and capable of punching a hole 42 in. by 16 in. through a plate 3/4 in. thick. There are provided dies for forming flanges 4 ft. 6 in. deep in the widest of plates.

Plate XLIII.

PUNCHING AND SHEARING.

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The modern practice of joggling and of scarfing the laps and edges of plates is applied in many instances, and special hydraulic tools are provided to carry out this work. The firm were also early in adopting the practice of joggling frames, deck beams, etc. The frames and beams are joggled when cold, to suit each alternate inner strake of plating, in a special design of hydraulic press, of which there are several in the works. This tool, illustrated on [Plate XLI]., adjoining page 95, carries dies on the ram-head and on the anvil, to form between them the obverse and reverse sides of the dent or joggle desired. Movable centre-pieces on the ram-head and anvil are traversed in all directions by screw thread to suit the position and width of the joggled part, and a gauge shows variations of 0.1 in. in the position of the joggled part of the frame. A 2 ft. length of angle can be joggled at each stroke. The machines are by Messrs. Hugh Smith and Co., Limited, Glasgow.

The same machine joggles the lap or edge of a shell, inner bottom, or deckplate in a similar way. The whole length of the frame or plate can thus be worked in a very short time. A powerful jib crane, of 16 ft. radius, assists materially in the rapidity of the work turned out by these tools. The only slips required are at the ends of the vessel, where the bevel of the frames precludes the use of joggling. A special electrically-driven hammer is used for forming these taper slips.

The angles, etc., to form the frames are assembled at the head of the building-berth, and when lying on skids are riveted to form the double bottom, frames and margin plates. Hydraulic riveters are used wherever possible. There are about a score of these at work in the shipbuilding yard, with cylinders from 8 in. to 10-1/2 in. in diameter, a stroke of 7-1/2 in., and a gap of 55 in., so that heavy work can be done. Some of them are specially designed for keel work, for closing rivets in beams, and for difficult parts.