GB659911A - Improvements in or relating to drilling tools - Google Patents

Abstract

659,911. Drill-bits. STANDARD OIL DEVELOPMENT CO. Feb. 25, 1949, No. 5259. Convention date, May 3, 1948. [Class 85] A drill bit incorporating a device for warning the operator when excessive wear of the blade has occurred during operation, comprises a hollow body 10 secured detachably to a stem 11, a blade 13 fixed to the lower end of the body, a duct 12. for conveying drilling fluid under pressure from the stem 11, and a duct 15 connected to a tube 17 which is sealed at its lower end and extends below the body 10, the tube being fixed to the body and blade 13. Ducts 12, 15 may be provided for each blade with the outlet surfaces of the ducts 15 preferably communicating with the back faces of the blades. The tubes, blades and body may be connected by welding, and sealed side-passages 171, 18<SP>1</SP> formed in the tubes 17, 18 adjacent the reaming edges 20, 201 of the blades. In operation, the blades may wear until the soft metal plugs either in the lower ends of the tubes 17, 18 or side passages 171, 18<SP>1</SP> are worn through, when the drop in fluid-pressure in the stem resulting from the additional escape passages is noticed (e.g. by the pressure fluid pump-motor racing) and the drill removed for replacement of the bit. Finemesh screens may be positioned in the ducts 15 to prevent the entrance of foreign matter. Each blade may be provided with a plurality of ducts and tubes 17, 18.