| 摘要 |
PURPOSE:To increase the stiffness in the radial direction of a base metal, to generate no deflection and chamber of the base metal during cutting and to eliminate the barrel rubbing of the base metal by forming on the base metal a plurality of cutting lines extending toward the outer peripheral part from the inner peripheral part thereof, and bending at least the side parts of the cutting lines almost in parallel thereto. CONSTITUTION:Bending parts 16, 19, 21, 24, 26 are formed on a base metal 10 along cutting lines 15, 18, 20, 23. Accordingly the stiffness in the radial direction of the base metal 10 is increased and the barrel rubbing can be prevented even in the case that the outer peripheral part of the base metal 10 is thermally expanded. Moreover, due to the action 4 wiping off a chip from the cutting face being obtained according to the rotation of a grindstone by forming the bending lines 16, 19, 21, 24, 26, the discharging property of chips is increased and also cutting resistance can be reduced. |
