| 摘要 |
PURPOSE:To obtain a drill whose shape is simple, grinding is easy and machining performance is superior, by welding a cemented carbide material on the central part of the tip part of a drill shank. CONSTITUTION:A rectangular groove having a certain depth in a diametral direction of a drill is provided on the tip part of the shank 1 of a drill, in which a rectangular cemented carbide tool blank 2 whose thickness (t) is inserted in a adhering state and both of them are secured by welding. The titled drill is so constituted that a relation of t=C.D<1/2> (provided that C=0.9487) is satisfied when an angle of 130-140 deg. and two-stepped flank are formed as a point angle of a cutting edge, an angle of inclination of 2.4-4.5 deg. is given to a chisel edge to be formed of a crossing line between flanks and as the diameter of drill and the thickness of a cemented carbide material Dmm. and tmm. are given respectively. |
