Hole forming tool

摘要

A hole forming tool (1) has a main body (2) constructed of a cemented carbide comprising 10 +/-2 wt% Co, 0.65 +/-0.25 wt% Cr, WC for the balance, and inevitable impurities. The average particle diameter of WC is in the range of 0.1 to 1.0 mu m, and a radial rake angle ( beta ) of cutting edges (8) formed at the end of the hole forming tool (1) is set to a negative value in the range of -5 DEG to -10 DEG . Chip discharging grooves (6) of which the helix angle (&thetas;) is in the range of 5 DEG to 15 DEG are formed in the exterior surface (4a) of the hole forming tool (1). A groove width ratio of land portions (10) and the chip discharging grooves (6) is in the range of 0.9 to 1.1. A point angle ( gamma ) is in the range of 125 DEG to 135 DEG , and a core diameter is in the range of 0.38D to 0.42D, in which D is the outside diameter of the drill. The main body (2) of the hole forming tool (1) is coated with a TiAlN layer (16).