Cutting head for drilling tool has central spike and two diametrically-opposed main cutting edges and sharp edge-cutting teeth at ninety degrees to main cutting edges

摘要

The cutting head (3) and shaft (2) of the drill (1) have two flutes (4,5). The leading edges of the flutes start at the outer edges of the main cutters (8), which have straight sharp edges at right-angles to the axis (6) of the drill. There are sharp teeth (10,12) at the trailing edges of the flutes, set at ninety degrees to the main cutters. There is a central spike (7).