A pneumatic tool consists of a cylinder with a handle, which contains a working (percussion) piston with various air ports, a cap nut, and a spring. Air is usually supplied to pneumatic tools from air tanks. The air is pumped into the tank by means of a motor and a pump and the pressure in the tank is regulated to 7 atmospheres, the motor starting and stopping automatically. The air is conducted through flexible tubes lined with materials capable of withstanding this working pressure of 7 atmospheres. Figures 57, 58, and 59 show important types of pneumatic tools.

Fig. 57. - Wood-boring Machine Operated by Compressed Air.

Fig. 58. - Pneumatic Hammer. Used in chipping rough metal off a fire box.

Fig. 59. - Pneumatic Drill. Partly in section.