To provide a structure holding a diamond abrasive grain layer more effectively deeply firmly to a base metal part tip end edge of a cutting edge, and maintain high rigid long life and high efficient cutting work ability continued.

In a blade part tip end edge of a blade base metal 1, a slit groove of 0.1 to 0.3 mm width 0.2 mm or less depth is provided successively in line with an equal space of 0.2 to 5 mm, and a groove part of the slit is charged with a super hard abrasive grain 2 of diamond, a blade part tip end protruded part of the slit is deformed by a rolling roller, to be mechanically caulked. In this way, a diamond abrasive grain layer is fixed to the inside of the slit groove, and to a tip end peripheral edge of a blade, electro deposition treatment of diamond or nickel plating treatment is applied.