PURPOSE: To adjust the diameter of a shaft part by surrounding the machined shaft part by all three shoes in the condition that each of the shoes has a abrasive belt-pressed recessed surface and the periphery of the machined shaft part is tightened.

CONSTITUTION: A first shoe 7 has a pressed recessed surface extending to an angle slightly smaller than 180° so as to press an abrasive belt 9 against a machined shaft part 6. Each of two second shoes 8a and 8b has a pressed recessed surface extending to an angle slightly smaller than 90° so as to press the abrasive belt 9 against the shaft part 6. When the shoes 7 and 8a and 8b are tightened, the shoe 7 surrounds approx. half or more of the shaft part 6, and each of the second shoes 8a and 8b surrounds approx. one-fourth or less of the shaft part 6. Two free spaces opposed to each other with respect to a diameter are produced between two angular end parts of the upper shoe 7 and an upper angular end part corresponding to each of the lower shoes 8a and 8b.