| 摘要 |
PURPOSE:To prevent the breakage of a tip by forming a rake face both with a projectedly curved surface that is formed on the side being continuous to a cutting edge and curved to the outside of the tip body in the circumferential direction and with a plane part that intersects this projectedly curved surface at an obtuse angle and continuous to the sharp side part on the opposite side of the side cutting edge. CONSTITUTION:The projectedly curved surface 7 constituting race faces 6A, 6B is formed so that it is curved to the outside of a tip body 1 in the circumferential direction of the upper and lower surfaces 2, 3 while inclining toward the central side of the lower surface 3 or the upper surface 2 as it goes apart from the cutting edge 5A, 5B. In the plane surface 9 that is continued to the sharp side part intersecting this projectedly curved surface 7 at an obtuse angle and being opposite to the cutting edges 5A, 5B on the side, or continued to the sharp side part 8 on the side where the cutting edges 5A, 5B of the upper and lower planes 2, 3 are not formed, the angle beta making with the direction of the thickness of the tip is made larger than the angle alpha of the projectedly curved surface 7, and is set to be approximately 18 deg. |
