| 摘要 |
There is disclosed an air motor adapted to rotate and axially shift an arbor having an annular cutter attached thereto. Within the arbor a plunger is slideably arranged with its leading end bearing against a pointed pilot pin at the center of the cutter. The plunger is biased forwardly by either a spring cartridge or a piston-cylinder assembly so as to apply a predetermined constant or programmable pressure on the pilot pin throughout the entire cutting cycle. When the cutter penetrates through the under face of the workpiece, the pressure on the plunger is reduced to a very low value so that the slug within the cutter will be ejected at a relatively slow safe velocity. |
