To precisely grind an edge such as a bevel type chisel having an elliptic cross section by continuously adjusting the angular position of a seat for grinding the sharp edge of a tool having a bevel.

This jig has a housing 1, and the housing 1 stores a seat 2 and is provided with a notch 3 on one short side. A screw 4 is provided on a short side on the opposite side to the seat 2, and a counter-stay 5 is provided at the inner end. The seat is locked at the prescribed position of the housing 1 by a lock screw 6. A tool 9 is inserted into the seat 2, the end section is positioned, and the tool 9 is locked to the seat 2 by the screw 4. The seat 2 and the tool 9 are extended outward perpendicularly from one end section 10 of the housing 1. The perpendicular position is automatically set by pressing the seat 2 to a shoulder section in the passage of the housing 1 when the lock screw 6 is rotated around its center. The seat 2 is rotated to the required angular position after being loosened from the housing 1 via the lock screw 6, then the seat 2 can be locked again to the housing 1 via the lock screw 6.