| 摘要 |
In a machine tool, a cradle of a bit holder is in the form of a rectangular trihedron and is inclined transversely about an axis of inclination corresponding to a generatrix of the conical bearing surface of a valve seat that has to be produced, while the cutting edges of the bit are produced from a blank having three bearing faces forming a rectangular trihedron, including a back face, a longitudinal face and a rear face, and another longitudinal face and a forward face of which, remaining in the as-produced state, are flanks with respect to the front face, a main cutting edge being produced so that its mid-point coincides with a reference point on the axis of inclination and lies on the axis of inclination at a constant distance from the vertex of the trihedron of the cradle. |
