PNEUMATIC TOOLS, a class of tools which operate by compressed air. They are usually portable, and used for metal, wood or stone work. The tools are of great variety and are put to many uses, but all of them are one of two types— percussion or rotary. In both types the motor is contained in the tool, and air under pressure is conducted to the tool by a hose.
Percussion Tools.—Tools of this type are the air hammer, clippers, chippers, caulkers, balast tappers, riveters, etc. The action in all is essentially the same. Air, under pressure of 85 to 100 pounds per square inch (except in the case of riveters where it is under higher pres sure) is sent into a cylinder containing a piston, which is made to reciprocate in the cylinder by proper valve action, the tool is supported in the front end of the cylinder, and transmits the blow received from the piston to the work. George Law, an Englishman, invented the first pneumatic tool, a percussion rock drill, in 1865. In this tool, as in most which have followed, the opposite end of the drill from the tool end was fitted with a handle and a controlling throttle. Boyer of St. Louis, Mo., invented the chipping hammer in 1896, and in 1899 Keller brought out the first valveless hammer, in which there is no valve be yond the position of impact, while the valve hammers are fitted with a recipro cating valve which regulates the inlet and exhaust of the driving air. Modern engineering has introduced many im provements and refinements and many patents have been issued on various meth ods of actuating and controlling the de vice. In general the valve type has a
longer stroke, and a more powerful blow than the valveless type, while the latter operates at a much higher rate of speed, sometimes over 20,000 strokes a minute, and it is claimed (which claim is not uncontested) by some engi neers that valveless types have a much longer life and are less liable to get out of order. The percussion tools vary in size from a small hand hammer to the large stationary plate riveter weigh ing tons.
Rotary Tools.—The principal rotary pneumatic tools are the drills, reamers, etc. They are made in a great range of sizes, and are used for many things, such as drilling wood and metal, reaming boiler tubes, grinding valve seats and cylinders, polishing and grinding. The rotary tools usually operate under a pres sure of about 75 pounds per square inch. The motor may be of the rotary type or of the reciprocating type with either fixed or oscillating cylinders, operating on a crank shaft to which the tool is fastened by a suitable mechanism. The great demands on the part of the shipyards for pneumatic tools of all types at the time of the World War gave even greater impetus to the already great and fast growing industry of manufacturing peumatic tools.