| 摘要 |
PROBLEM TO BE SOLVED: To increase the rake angle of a rake surface of a cutting edge on the center side of a drill as it is distant from the rotational center. SOLUTION: A grinding wheel 7 is formed of a rotational disc, a side part grinding surface 71 is formed near the outer peripheral part on one side surface of a grinding wheel main body 73, the side part grinding surface 71 is formed into a curved surface so that the projecting amount in the perpendicular direction may be increased on the grinding wheel main body 73 as it is close to the outer peripheral end, and the side surface grinding surface on the outer peripheral end is a device for grinding a drill center side cutting edge by using the grinding wheel formed in the surface direction of the grinding wheel main body. |
