| 摘要 |
PURPOSE:To enable counterboring operation to be performed correctly and quickly, by providing a cylindrical insulating layer on a cutting tool eccentrically with respect to the rotational axis of the tool, so that outer and inner annular blades divided into two sections by the cylindrical insulating layer are insulated electrically from each other. CONSTITUTION:A tool drive starting switch 9 is pushed so that a rotating cutting tool 1 is lowered and caused to cut an outer copper foil layer 10a on a multilayer printed circuit board by a tool drive control device 8. On this occasion, an outer annular blade 4 is electrically connected with an inner annular blade 4 by the first layer, namely the outer copper foil layer 10a. A conduction signal produced thereby is sent to a conduction signal control device 7 via slip rings 5, 6 and counted by the device 7 so that the arrival of the cutting tool at the outer copper foil layer 10a is recorded. The cutting operation is further continued until the cutting tool reaches a reference position mark 14 on an inner copper foil layer 13. A conduction signal generated in this moment is processed as a counterboring finish signal by the conduction signal control device 7 so that the counterboring operation is stopped by the cutting tool drive device 8. |
