Drill bit for manufacturing holes in workpiece made of e.g. glass-fiber reinforced plastic, has splinter groove partially formed on minor cutting edges such that rake angle of minor cutting edges is enlarged in region of groove

摘要

The bit (1) has minor cutting edges (19, 19') provided in a region of a peripheral surface (17) of the bit, where a splinter groove (21) is formed in the minor cutting edges. Another splinter groove (25) is partially formed on the minor cutting edges such that a rake angle of the minor cutting edges is enlarged in a region of the latter groove. The minor cutting edges are attached to major cutting edges (3, 3'), and comprise two longitudinal portions, where width of a round cross section chamfer (23') in a region of one of the portions is smaller than in a region of the other portion.