Also found in: Dictionary, Thesaurus, Wikipedia.
pneumatic hammer[nu̇′mad·ik ′ham·ər]
a hammer in which the working body is compressed air, which provides an elastic coupling between the compressor and working pistons. Air from a compressor is supplied to the working cylinder and, by means of the piston and a crank mechanism, imparts reciprocating motion to the dropping parts (a hollow drop weight, which is at once the piston and rod of the working cylinder). Pneumatic hammers have a separate electric drive.
In a single-action pneumatic hammer, the drop weight is raised as a result of the rarefaction created in the working cylinder when the piston of the compressor cylinder moves downward. In a double-action hammer the upper and lower cavities of the compressor’s cylinder are connected to the upper and lower cavities of the working cylinder, respectively. The drop weight falls when the compressor piston moves upward and is raised when the piston moves downward. Regardless of the height of the workpiece being forged, the number of blows struck by the drop weight is equal to the number of revolutions of the crankshaft.
Pneumatic hammers are used mainly for smith forging on flat or indented dies. Soviet industry produces pneumatic hammers with dropping parts weighing 30–100 kg; the speed of the dropping parts at the moment of impact is 5 m/sec for small hammers (up to 200 strokes per min) and 7.5 m/sec for large hammers (up to 95 strokes per min).