Rotary drill bit shank, rotary drill bits so equipped, and methods of manufacture

A rotary drill bit for drilling a subterranean formation, comprising:

• a bit body having a centerline and including a leading end for contacting a formation during drilling;
• a shank structure, comprising:
• at least one tapered feature matingly engaging a complementary feature of the bit body and at least in part positioning the shank structure in relation to the bit body;
• and
• a trailing end having structure associated therewith for connecting the rotary drill bit to a drill string;
• a weld recess substantially formed by at least one surface of the shank structure and at least one surface of the bit body;
• a multi-pass weld affixing the shank structure to the bit body substantially disposed within the weld recess, comprising:
• a first weld originating from a first circumferential position and having an associated circumferential extent;
• and
• a second weld originating from a second circumferential position and having an associated circumferential extent;
• wherein the second circumferential position and the first circumferential position are separated by a distance of at least about one quarter of the associated circumference of the first circumferential position;
• and
• at least one cutting element secured to the bit body.

A method of fabricating a rotary drill bit, comprising:

• providing a shank structure for attaching the rotary drill bit to a drill string configured with at least one tapered feature for positioning the shank structure;
• providing a bit body having an end configured for drilling a subterranean formation, the bit body including at least one complementary tapered feature for positioning the shank structure in relation thereto;
• positioning the shank structure by matingly engaging the at least one tapered feature of the shank structure and the at least one complementary tapered feature of the bit body and defining a weld region between the shank structure and the bit body;
• forming a first weld originating from a first circumferential position within the weld region;
• forming at least a second weld originating from a second circumferential position within the weld region;
• wherein the second circumferential position and the first circumferential position are separated by at least about 90° in relation to the centerline of the bit body.

A method of fabricating a rotary drill bit, comprising:

• providing a shank structure for attaching the rotary drill bit to a drill string;
• providing a bit body having an end configured for drilling a subterranean formation;
• positioning the shank structure in contact with the bit body and defining a weld region between the shank structure and the bit body;
• and
• forming at least one weld within the weld region in the absence of preheating of at least the shank structure.

A rotary drill bit for drilling a subterranean formation, comprising:

• a bit body having a centerline and including a leading end for contacting a formation during drilling;
• a shank structure, comprising at least one frustoconical feature matingly engaging a complementary frustoconical feature of the bit body;
• a weld recess substantially formed by at least one surface of the shank structure and at least one surface of the bit body;
• at least one weld affixing the shank structure to the bit body substantially disposed within the weld recess;
• and
• at least one cutting element secured to the bit body.

A shank structure for a rotary drill bit, comprising:

• at least one feature for engaging a complementary feature of a bit body;
• a trailing end having structure associated therewith for connecting the rotary drill bit to a drill string;
• and
• wherein the shank structure comprises a material having a carbon equivalent less than about 0.35%.