Abstract: A rotary drill bit, or a drill tip for use in such a drill bit, has a cutting edge extending outwardly away from the axis of rotation of the bit and defined by the intersection of a frontal face, inclined with respect to a plane normal to the axis of rotation of the bit, and a leading face, inclined with respect to a plane containing the axis of rotation of the bit, the angles which said frontal and leading faces make with said planes respectively both decreasing as said faces extend away from the axis of rotation of the bit. The decrease in the angles is such that the included angle between the frontal face and the leading face, the clearance angle and the effective rake each remain substantially the same at all points along the length of the cutting edge.

Abstract: A tool holder has a socket to receive the shank of a tool, a transverse bore breaking into the socket, and a tool retaining device for insertion in the transverse bore comprising a rigid retaining pin bonded to a resilient member which urges the retaining member sideways so that part of the retaining pin projects into the socket to engage the shank of a tool inserted therein. An elongate element is bonded to the resilient element and includes, at opposite ends thereof, stop members which overlie surfaces of the tool holder surrounding the ends of the bore, and thereby prevent longitudinal movement of the retaining device in the transverse bore. The stop members may be moved, by deformation of the resilient member, to a release position where they lie within the cross-section of the transverse bore, so that the retaining device may be inserted into, or withdrawn from, the bore.

Abstract: A male member is connected to a female member by providing a rolling location element between a wall of the male member and a relatively inclined cooperative wall of the female member and biasing the location element into a position in which, should any attempt be made to remove the male member from the bore of the female member, a wedging action is obtained which prevents removal of the male member.