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US 6,148,936 AGranted
Methods of manufacturing rotary drill bits
AssigneeCamco International (UK) Limited
InventorsStephen Martin Evans, Andrew Bell
Life of this patent
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AssigneeCamco International (UK) Limited
InventorsStephen Martin Evans, Andrew Bell
Estimating the term…
A rotary drill bit is manufactured by a powder metallurgy process by placing a metal mandrel in a mold, packing the mold with particulate matrix-forming material, infiltrating the material with a molten binding alloy, and cooling the assembly to form a solid infiltrated matrix bonded to the mandrel. The mandrel comprises an outer part surrounded by the matrix-forming material and an inner part, secured to the outer part but out of contact with the matrix-forming material. The outer part of the mandrel is formed from a material having thermal characteristics close to those of the matrix, so as to reduce the tendency for the matrix to crack under thermal stress, while the inner part of the mandrel is formed from a precipitation-hardening material, the strength and hardness of which increases in the infiltration process and the subsequent heating/cooling cycle for brazing the cutters on to the drill bit. The threaded shank of the drill bit is formed directly on the inner part since it will have sufficient strength and hardness for this purpose.
A method of manufacturing a rotary drill bit comprising a bit body having a threaded shank for connection to a drill string and a leading face on which cutters are mounted, the method including the step of locating a metal mandrel within a mold, packing the mold around at least part of the mandrel with particulate matrix-forming material, infiltrating said material at elevated temperature with a molten binding alloy, and cooling the material, binding alloy and mandrel to form a solid infiltrated matrix bonded to the mandrel, the mandrel being formed in at least two parts including an outer part surrounded by a main body of said matrix-forming material and an inner part which engages with the outer part of the mandrel and is out of contact with said main body of matrix-forming material wherein said inner part is brazed to said outer part by the molten binding alloy.
A rotary drill bit comprising a bit body having a threaded shank for connection to a drill string and a leading face on which cutters are mounted, the bit body comprising a metal mandrel, around part of the outer surface of which is formed a main body of solid infiltrated matrix material comprising a particulate matrix-forming material and a binding alloy, said mandrel comprising an outer part surrounded by said main body of solid infiltrated matrix material, and an inner part which engages the outer part, said inner part being formed of an alloy which has been precipitation hardened material wherein said inner part is brazed to said outer part by the binding alloy.
Dependencies are inferred from the claim text.