Abstract: A rotary borer has a body (10) mountable on a drill steel and one or more cutting tips (30) at a front of the body (10). Each tip (30) is tapered and is frictionally received in a corresponding tapered slot (22) in the body (10). The slot (22) has a trailing, rigid anvil surface (16), which extends almost to the extremity of the tip (30) to support the tip (30) and to locate it laterally, and a leading, resilient retaining surface (20) well shy of the extremity of the tip (30) to expose a portion of the tip. The tip (30) is readily replaceable. Release of the tip can be effected by heat or by means of taper drift (38) for which a transverse hole (37) is provided proximate a bottom of the slot (22).

Abstract: A drill bit is fictionally received over a drill rod via complementary generally frusto-conical male formation and socket. The socket has an inwardly protruding face at an angle with the longitudinal axis of the drill rod. The male formation on the drill rod has a depression in the form of an area where the convexity of the frusto-conical portion has been flattened at an angle so as to form a rocking formation at a selective location relative to the opposite ends of the male formation and the socket. A clearance space diverges away from the rocking formation toward a selective ends of the male formation and the socket. The frusto-conical male formation and the socket are a-circular and form positive driving engagement between the drill rod and the drill bit. An impact at the point of maximum clearance causes rocking about the rocking formation to break static friction and to facilitate release of the drill bit from the drill rod.