PURPOSE: To secure shape precision by suppressing the pressing pressure of the abrasive material arranged on the both surfaces of a revolving thin disc-shaped workpiece by maintaining the difference of the both magnetic forces to a certain value or less, in the working for a magnetic disc, etc.
CONSTITUTION: The soft abrasive material 14 which is installed onto the inner surface of a pressing tool 13 and contains grinding grains is arranged in symmetrical form onto the both surfaces of a thin disc-shaped workpiece 1 held by a rotary jig 2, and each abrasive material 14 is pressed onto the both surfaces of the workpiece 1 by the cooperation of an electromagnetic coil 8, magnetic rod 10, and a spring 16. Said pressing pressure is measured by a load sensor 12 integrally formed with a shock absorber 11, and said pressing pressure is controlled so that the pressing pressure onto the both pressing tool 13 is set to a prescribed value, keeping the difference of the both electromagnetic forces generated in the electromagnetic coil 8 to a certain value or less. Therefore, mirror- surface finishing is permitted, securing the precision of the shape of the thin disc-shaped workpiece having a thickness of 10μm or less.
KAMATA HIROSHI
DAIKU HIROYUKI
