Patent ID: 7419017
Filing Date: 2008-09-02
Classification: E21B

Abstract:
1. A method of coupling a shank with a drill bit to avoid the application of a rotational shear force on a retaining member of the coupled shank and bit when rotating the shank relative to the bit and avoid the application of a downward shear force on the retaining member when applying percussive axial force to the shank during drilling and when applying an extraction force to the shank to upwardly lift the shank coupled to the bit there is a shear force applied to the retaining member comprising: a. providing a shank having a center stud that can fit into an opening in a bit when the bit and the shank are assembled, the center stud having a shank passage; b. providing a bit having a bit passage, the bit has an opening to receive the center stud when the bit and shank are engaged; c. providing a retaining member; d. providing a complementary lug and pocket structure in which the shank has either a pocket or a lug and the bit has either a complementary lug or pocket in which the lug and pocket are engaged when the bit and the shank are engaged; e. engaging the shank with the bit and engaging the complementary lug and pocket structure; and f. inserting the retaining member through aligned passages of the shank and the bit, wherein the bit passage, shank passage, retaining member, shank and bit are configured and combined in such a manner that when a downward percussive axial force is applied to the shank and transmitted to the bit while drilling there is no shear force applied to the retaining member and when rotating the shank relative to the bit there is no shear force applied to the retaining member and when upwardly lifting the bit coupled to the shank there is a shear force applied to the retaining member.