To facilitate positioning of a chip saw or the like on a polishing wheel in a holder for mounting the chip saw mounted on a disc grinder by fitting a fulcrum pin set on a disc cover and a stopper pin in bottom parts between blades respectively.

A holder 1 is provided, at its rising part 1c, with oblong holes 6, 7 in which one end of each mounting plate 8a or 8b is fixed by a screw 9a on 9b and a wingnut. In the other ends thereof a headed fulcrum pin 11 and a headed stopper pin 12 are screwed respectively. In polishing a chip saw, it is abutted on the part 1b and the pin 11 is fitted in one bottom part while the pin 12 is fitted in the bottom whose direction corresponds to the circumference centering the pin 11. After both plates 8a, 8b are adjusted so that the back of the blade between the pins 11, 12 abut on a diamond wheel 3, they are fixed by means of the wingnuts.