| 摘要 |
PURPOSE:To use a tap holder with large grasping force and rigidity, by forming a relief angle to at least 1 deg. and arranging accuracy of a shank equally to or above a shank of an end mill of the same nominal diameter to decrease cutting torque in case of tapping a material difficult to cut. CONSTITUTION:A relief angle of a tapping thread is formed to at least 1 deg. in either case providing the relief angle 3 left with a margin width 1 or providing the angle 3 from an edge point. A shank of a tap is formed to a thick shape and accuracy of an end mill shank, in which, accuracy of a permissible difference out of roundness and cylindricity is increased, and a milling chuck with large grasping force and rigidity can be used for a tap holder. |
