PURPOSE: To facilitate attaching/detaching of a tip, and precisely regrind the tip by providing a presser shaft for pressing the tip from above, and a sliding plate which can freely slide to right and left on a base provided with a supporting plate, and providing a pair of right and left ball bearings for contacting and backing up the outer peripheral surface of the circular piece tip.

CONSTITUTION: A circular piece tip to be ground is nipped between a presser shaft 5 and a supporting plate 4, and energizing by a spring 8 to be pressed against the supporting plate 4. In this case, the abutting surfaces wherein the presser shaft 5 and the supporting plate 4 abut on the circular piece tip, are covered with rubber caps 6 to stably fix the tip without sliding. The presser shaft 5 is moved up and down by rotatively operating a handle 7, and by rotation of the handle 7, a shaft 12 is also rotated through engagement of gears 10, 11. The shaft 12 is fixed integrally with a knurled handle 13. In the bottom face of a sliding plate 14, a V-shaped notch is provided, and a pair of ball bearings 15 fitted thereto bear the outer peripheral surface of the circular piece tip.