Contact detecting apparatus

摘要

A contact detecting apparatus for detecting the contact of a workpiece with a tool in a machine tool which comprises a coil mounted on the periphery of a spindle head and connected to an AC power source for generating an induced current in a looped secondary circuit including the workpiece, a work table, a machine body, a spindle head, a tool spindle and the tool, when the workpiece and the tool are moved relatively into contact with each other. Bypassing elements are included in the secondary circuit for bypassing an electric resistance in spindle bearings. A detector is connected between the AC power source and the coil for detecting a change in an electric signal caused by the contact between the workpiece and the tool.