Abstract: A retractable drill bit system 10 comprises a drive sub 18 which is adapted for connection to a lower end of a drill 12, a tool 20 for installing and retracting drill bit segments 22 from the drive sub 18; and an insert 24 for selectively locking the bit segments 22 to an end of the drive sub 18 and releasing the bit segments 22. A plurality of recesses 5B are formed about an inner circumferential wall at one end of the drive sub 18 and a landing seat 32 formed about the inner wall upstream of the recesses 58. The area of the interior wall between the landing seat 32 and recesses 58 is profiled with a series of tapered and level surfaces. The tool 20 includes a slidable cradle 176 extending from one end about which the bit segments 22 are held during installation and retrieval. The bit segments 22 being held in place about the cradle by an elastic band 198.

Abstract: An insert for releasably retaining drill bit segments in a ground drill takes the form of a cylindrical tube movable within the ground drill between an installation position and a retrieval position. A pair of opposing tapered peaks extends from the upstream end of the insert. Sides of the peaks slope sharply in a downstream direction and lead to flats separating the peaks. When a running tool with radially extending latch dogs travels down the drill, the latch dogs contact the peaks to cause the tool to rotate about its longitudinal axis. When the latch dogs hit the flats they engage the insert, pushing it down into the installation position and locking the bit segments into a cutting position. Another set of latch dogs provided on the tool can engage slots formed in the insert to pull the insert upwardly and release the bit segments.

Abstract: A retractable drill bit system 10 comprises a drive sub 18 which is adapted for connection to a lower end of a drill 12, a tool 20 for installing and retracting drill bit segments 22 from the drive sub 18; and an insert 24 for selectively locking the bit segments 22 to an end of the drive sub 18 and releasing the bit segments 22.A plurality of recesses 5B are formed about an inner circumferential wall at one end of the drive sub 18 and a landing seat 32 formed about the inner wall upstream of the recesses 58. The area of the interior wall between the landing seat 32 and recesses 58 is profiled with a series of tapered and level surfaces.The tool 20 includes a slidable cradle 176 extending from one end about which the bit segments 22 are held during installation and retrieval. The bit segments 22 being held in place about the cradle by an elastic band 198.

Abstract: A retractable drill bit system 10 comprises a drive sub 18 which is adapted for connection to a lower end of a drill 12, a tool 20 for installing and retracting drill bit segments 22 from the drive sub 18; and an insert 24 for selectively locking the bit segments 22 to an end of the drive sub 18 and releasing the bit segments 22.A plurality of recesses 5B are formed about an inner circumferential wall at one end of the drive sub 18 and a landing seat 32 formed about the inner wall upstream of the recesses 58. The area of the interior wall between the landing seat 32 and recesses 58 is profiled with a series of tapered and level surfaces.The tool 20 includes a slidable cradle 176 extending from one end about which the bit segments 22 are held during installation and retrieval. The bit segments 22 being held in place about the cradle by an elastic band 198.

Abstract: A retractable drill bit system (10) comprises a drive sub (18) which is adapted for connection to a lower end of a drill (12), a tool (20) for installing and retractable drill bit segments (22) from the drive sub (18); and an insert (24) for selectively locking the bit segments (22) to an end of the drive sub (18) and releasing the bit segments (22). A plurality of recesses (5B) are formed about an inner circumferential wall at one end of the drive sub (18) and a landing seat (32) formed about the inner wall upstream of the recesses (58). The area of the interior wall between the landing seat (32) and recesses (58) is profiled with a series of tapered and level surfaces. The tool (20) includes a slidable cradle (176) extending from one end about which the bit segments (22) are held during installation and retrieval. The bit segments (22) being held in place about the cradle by an elastic band (198).