| 摘要 |
A loose top for drilling tools, including front and rear ends, a pair of envelope part surfaces concentric with a center axis, and two chip flutes countersunk in relation to the pair of envelope part surfaces between which two bars project radially from a central core, the front end including a cutting edge and at least one clearance surface positioned rotationally behind the cutting edge, the rear end forming an axial contact surface. The loose top includes two opposite side contact surfaces against which elastically bendable branches of a tool basic body are pressed in use, a pair of convex guide surfaces situated axially behind the side contact surfaces, the guide surfaces being concentric with the center axis and radially spaced-apart from the center axis at a distance that is less than the radial distance between the center axis and a respective side contact surface, and a pair of torque-carrying tangential contact surfaces that are situated radially inside the envelope part surfaces and outside the side contact surfaces. The axial contact surface extends perpendicular to the center axis between borderlines adjacent to the two envelope part surfaces. |
