Patent ID: 6881133

Claim:
A grinding method for a vertical type of double disc surface grinding machine for a workpiece in which a pair of vertically opposing upper and lower grinding wheels are rotatably driven by grinding wheel rotation drive motors and vertically driven by grinding wheel vertical drive motors respectively, and both grinding wheels are fed from waiting positions vertically apart from respective upper and lower ground surfaces of a workpiece to a grinding end positions so as to carry out the surface grinding simultaneously on the upper and lower ground surfaces of the workpiece, the movement from the waiting position to the grinding end position being termed the entire vertical moving stroke; wherein: the entire vertical moving stroke of the grinding wheel includes: an idle feed stroke in which the grinding wheel moves at a specified idle feed speed from the waiting position to a detection start position before contacting with the ground surface; a detection stroke in which the wheel moves at a detection speed lower than the idle feed speed from the detection start position to a detection end position after contacting with the ground surface, then the grinding wheel rotation drive motor detects a grinding start position; and a grinding stroke in which the wheel moves at a grinding speed from the grinding start position to a grinding end position; and the grinding start position is a position corresponding to a time where a current of the grinding wheel rotation drive motor detected during the detection stroke increases, by a specified amount, from a value at no-load condition up to a specified value.