PURPOSE: To detect a stable contact of less time lags by insulating a saw blade and the material to be out each other, meanwhile, connecting the series circuit consisting of a lower voltage power source and resistance and detecting the voltage variation at both ends of the resistances of said series circuit at the time when the saw blade is brought into contact with the material to be cut.

CONSTITUTION: After ascending a housing 5 the material W to be cut is fitted to a vice base 9, a saw blade 21 is driven and when the solenoid 57 of an electromagnetic direction switching valve 39 is excited, the press oil inside a cylinder 23 is discharged to a tank T from the valve 39 by passing an electromagnetic closing valve 45 mainly with the gravity of the housing 5 and the housing 5 is descended comparatively at high speed. When the saw blade 21 is brought into contact with the material W to be cut, a voltage difference is caused at both ends of a resistance 47 and the switching valve 45 is closed by a solenoid valve control circuit 51. The press oil is therefore passed through a flow control valve 41 and the flow is adequately limited here. Consequently the descending speed of the housing 5, i.e., the notching speed of the saw blade 21 is controlled to an optimum value at the cutting start time.