(19)

(11)

EP 2 872 724 A1

(12)

(43) Date of publication: 20.05.2015 Bulletin 2015/21 (21) Application number: 13816696.2 (22) Date of filing: 11.07.2013

(51) International Patent Classification (IPC):  E21B 10/46(2006.01) B24D 3/10(2006.01) (86) International application number: PCT/US2013/050048 (87) International publication number: WO 2014/011855 (16.01.2014 Gazette 2014/03)

(84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR Designated Extension States: BA ME (30) Priority: 11.07.2012 US 201261670500 P 15.03.2013 US 201313836963 (71) Applicant: Smith International, Inc. Houston, TX 77073 (US)	(72) Inventor: BAO, Yahua Orem, Utah 84058 (US) (74) Representative: Li, Boxi  Schlumberger Cambridge Research Limited Intellectual Property Law High Cross Madingley Road Cambridge CB3 0EL Cambridge CB3 0EL (GB)