Drill bit for percussive drilling

摘要

A percussion drilling bit operable when accorded only a limited range of angular movement about a longitudinal axis of the bit, and wherein the bit comprises cutting tips or inserts arranged in a series of rings or tiers concentric with said longitudinal axis, such that for a predetermined angle of rotation of the bit about said axis, the zone of action of each cutting tip or insert in each said ring or tier overlaps that of at least the adjoining cutting tips or inserts in the same ring or tier.