Abstract: A grinding wheel assembly includes a grinding wheel having two recesses respectively defined in tow opposite surfaces thereof and a plurality of protrusions extending inward from a inner periphery of each of the two recesses. A first position member is received in one of the two recesses and has first notches for receiving the protrusions therein. A tubular section extend from the first position member and a polygonal section is located on the tubular section. A threaded rod extends from the polygonal section and through a hole of the wheel. A second position member is engaged with the other recess and has second notches for receiving the protrusions. The second position member has a polygonal hole which is engaged with the polygonal section.