GB1323284A - Drill bits - Google Patents

Abstract

1323284 Percussive drill bits TARMAC ENG Ltd 13 March 1972 11597/72 Heading B4C [Also in Division E1] A percussive drill bit, e.g. for a down-hole drill, comprises a head portion 1, a shank portion 2, cutting inserts in the leading face 4, and a recess 11 in which a member 10 is located, the member being secured in the recess by a non-metallic setting compound which forms an interlock with the head and the member and/or bonds with the head and the member. At least one cutting insert is provided in the leading face 6 of the member 10. As illustrated, the member 10 includes a tapered spigot 12, the taper of which may be the same as or less than that of socket 13 to permit an interference fit therebetween so as to provide additional securing. A feed passage 29 enables introduction of the compound, which sets to provide, e.g. polyurethane or natural or synthetic rubber, into annular passage 28. The cutting inserts 14 in the leading face 4 and in the face 6 may be of the parallelepipedic type or the button (cylindrical) type. Passages 16-18 and flutes 19 permit passage of a flushing fluid to the leading face 4 and from the leading face 4 to the rear of the head. The member 10 may be such that the face 6 extends forwardly beyond the face 4 or substantially level therewith, and it may be removed from the recess if cutting inserts carried thereby are damaged. Instead of an interference fit being provided by a spigot and socket, a sleeve, or rings, of malleable metal such as copper are provided between the spigot and socket so that a the spigot is forced into the socket, the malleable metal is comprssed to additionally secure the member in the recess.