PURPOSE: To facilitate the work at the time of fitting a cutting grinding wheel to a disc sander, and to improve the angle of approach at the time of cutting.

CONSTITUTION: A device is formed of an inner flange 1 and an outer flange 2 respectively having each boss 11, 21, and a spacer 3, which can be fitted in these bosses 11, 21. The inner flange 1 is inserted into a rotary shaft 51 formed with a screw of a disc sander main body 5 in the condition that the boss 11 is directed outward, and the outer flange 2 is inserted into the grinding wheel 4 and the spacer 3 in this order, and screwed with the rotary shaft 51 in the condition that the boss 21 is directed inward, and the spacer 3 is made to tightly contact with the grinding wheel 4 and the inner flange 1. The outer flange 2 to be screwed with the rotary shaft 51 is formed with four holes 22 for a fastening wrench at a space of 90 degree.