(19)
(11) EP 0 511 547 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
14.04.1993 Bulletin 1993/15

(43) Date of publication A2:
04.11.1992 Bulletin 1992/45

(21) Application number: 92106450.7

(22) Date of filing: 14.04.1992
(51) International Patent Classification (IPC)5: E21B 10/16, E21B 10/52
(84) Designated Contracting States:
DE FR GB IT NL

(30) Priority: 01.05.1991 US 693900

(71) Applicant: SMITH INTERNATIONAL, INC.
Houston, Texas 77206 (US)

(72) Inventors:
  • Crockett, David P.
    Moorpark, California 93021 (US)
  • Hooper, Michael E.
    Spring, Texas 77388 (US)

(74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät 
Maximilianstrasse 58
80538 München
80538 München (DE)


(56) References cited: : 
   
       


    (54) Rock bit


    (57) A rock bit is disclosed having a plurality of rolling cone cutters each having a gage row of inserts oriented to face the borehole bottom for crushing the same, and a second row of heel gage inserts which are oriented to face the borehole sidewall for scraping the same. The heel row inserts are interleaved between the gage row inserts and the cutting surface profile of the heel row inserts overlaps the cutting surface profile of the gage inserts in order to alleviate most of the scraping action normally encountered by gage inserts. The crowns of the heel row inserts are within four millimeters up hole from the crowns of the gage row inserts. The heel inserts are made of a harder material than the gage row inserts for resisting the scraping action against the sidewall of the borehole.






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