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1. (WO1999009292) PARTIALLY ENHANCED DRILL BIT

Pub. No.:    WO/1999/009292    International Application No.:    PCT/SE1998/001469
Publication Date: Fri Feb 26 00:59:59 CET 1999 International Filing Date: Sat Aug 15 01:59:59 CEST 1998
IPC: E21B 10/56
Applicants: SANDVIK AB (publ)
Inventors: INGMARSSON, Karl
Title: PARTIALLY ENHANCED DRILL BIT
Abstract:
A partially diamond-enhanced drill bit includes a bit body, at leats one annular row of non-diamond enhanced buttons mounted in the bit body, and at least one annular row of diamond-enhanced buttons mounted in the bit body radially outside of the non-enhanced buttons. A total wear volume of the non-enhanced buttons in at least one row thereof is greater than 75 percent of a total wear volume of an outermost annular row of enhanced buttons. A number of non-enhanced buttons in one of the rows thereof is at least equal to a number of enhanced buttons in the outermost annular row thereof. At least some of the non-enhanced buttons have a greater wear volume than any of the enhanced buttons. The radially outermost row of non-enhanced buttons is displaced axially forwardly with respect to an adjacent row of enhanced buttons.