K = spring necking-tools used when locating the amount and distance the swaging is to be done along a shaft of iron or steel.

The hammer shown in Fig. 388 is a 1 cwt. size, in general use for light smithing. In this type, with overhanging slides, there is room for long bars to be placed between the standards.

Steam Stamp.-Another form is shown in Fig. 389, in which the tup is guided by round adjustable pillars. This hammer is used for stamping. The illustration represents a 10-cwt. size with a massive base block, on the top of which the lower die may be secured and adjusted by the bolster screws. The piston has a stroke of 30 in., and has at the top a spring buffer arrangement to prevent it striking the cylinder cover, as the piston returns to the top of stroke directly hand lever is released. Provision is, however, made for regulating the force of the blow, and the speed at which the tup rises off the work after the blow has been given.

Stamping Dies.-Ordinary dies may be fixed somewhat similarly to the fixing of a bolster in a punching machine. For ordinary methods see A and B, Fig. 390. Special methods of fixing dies for exceptional cases are shown at C, D, E, F and G. The dies should be so placed in the stamp that the centre of pressure upon the forging shall be as nearly as possible on the vertical centre line of the tup. This greatly relieves the strain upon the slides or piston rod of the stamp. A blast pipe is used to blow the scale out of the bottom die.

It is customary in using steam hammers and steam stamps to drain all the water from the steam pipes, so as to supply dry steam to the cylinder.

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Player's Patent Pneumatic Hammer. The hammer shown in Fig. 391 is driven by belt. The driving pulley is fixed to a steel shaft which works a "banjo" (better known as cross slide") by means of a slipper block, which causes the banjo attached to the cylinder to vibrate in a vertical direction. Inside the cylinder there is a piston which is kept air-tight in the usual way. The "tup" fixed to the piston rod carries the hammer which gives the blow. When the hammer is started the piston rises in the cylinder to its highest position, then, by means of a valve attached to the back of the cylinder, the tup can be gradually brought down with at first light blows, then heavier blows, as required according to the will of the operator, and is controlled by a foot or hand lever according to the size of the hammer.

The variation of the blow is caused as follows: Supposing the piston to be at its highest position, on pressing the treadle down or altering the

handle, as the case may be, the air is allowed to escape from underneath the piston, and as it is being drawn in both above and below the piston by the shifting valves, seen in front of the cylinder, it can be readily understood that by alteration of the controlling valve at the back of the

cylinder an instant alteration of the position of the piston in the cylinder is obtained. On releasing the foot or hand lever the cylinder draws in air below the piston, and forces the piston again to its highest position.

While the hammer is running, the piston is cushioning up and down in the cylinder ready to give an instantaneous blow.

The cwt. hammer (Fig. 392) gives 350 blows per minute, and the

7 cwt. hammer runs at

150 to 200 blows per minute. The brake, worked by hand lever, is used for stopping the hammer at any point of the stroke whilst running.

Pneumatic Tools.The "Boyer" riveter is used for riveting shell plates with rivets up to 1 in. diameter. The riveting hammer is mounted, and has a travel of 33 in. in an outer cylinder, to which air is admitted when the hammer trigger is depressed. The pressure, acting on a collar surrounding the hammer barrel, shoots the tool forward on to the rivet head, the notched bar at the other end of the rigging being adjusted to provide the reaction necessary for the snap to be continuously pressed on to the rivet, while the percussive riveting action is performed by the hammer.

FIG. 392.-Pneumatic belt-driven hammer.

The hammer with its casing is mounted in a spherical. bearing which enables it to be turned about through any desired angle within the requisite limits. In a more recent type the air is admitted through a throttle valve.