(19)
(11) EP 0 219 959 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
19.10.1988 Bulletin 1988/42

(43) Date of publication A2:
29.04.1987 Bulletin 1987/18

(21) Application number: 86306897

(22) Date of filing: 05.09.1986
(84) Designated Contracting States:
BE CH DE FR GB IT LI SE

(30) Priority: 18.10.1985 US 789120

(71) Applicant: SMITH INTERNATIONAL, INC.
 ()

(72) Inventor:
  • Hall, David Richard
     ()

   


(54) Rock bit with wear resistant inserts


(57) A rock bit has three cones with tunsgten carbide inserts in the cutting structure of each cone. The gage row inserts have a layer of polycrystalline diamond on the converging portion protruding from the surface of the cone. One or more transition layers are provided between the tungsten carbide insert body and the polycrystalline diamond layer. Such a transition layer comprises diamond and precemented tungsten carbide.







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