US Patent 7559382 Hard material head and rotary percussion drill bit

A hard material head (1) for a rotary percussion drill bit (2) having an elongated shaft (15) including at least three cutting edges (4) distributed circumferentially within a circumscribing circle, a bottom surface (6) located opposite the cutting edges (4) and fastened by a material bond to an end (8) of the drill bit shaft (15) of the rotary percussion drill bit (2), concave side surfaces (5) formed circumferentially between adjacent cutting edges (4), and a peripheral pocket (9) opening toward the bottom surface (6) and formed, respectively, in at least two concave side surfaces (5) located opposite one another, and in which a corresponding axial pin (10, 10′) formed on a shaft end (8) is form-locking engageable.