PURPOSE: To provide the optimum grinding conditions suitable for the given grinding purpose without remodeling a grinding attachment, by inserting a spacer having a proper hardness for the given grinding purpose, between a rubber disc and a grinding element.

CONSTITUTION: For a grinding operation required to eliminate surface roughness of a workpiece, a hard material such as stainless steel sheet is used for a spacer II to be inserted between a rubber disc 3 and a grinding element 9. While, a soft material such as sponge is used for the spacer II for the grinding operation required to make into convex or concave shapes on the surface of the workpiece.