Importance

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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. The insert 24 is provided at one end with a series of keyways 218 which locate over the bit segments 22 when the bit segments are locked to the drive sub 18. The insert 24 is always retained within the drive sub 18. Bit segments 22 are carried by the tool 20 to the drive sub 18 and locked in place by the insert 24. The tool 20 can then be withdrawn and the drill 12 operated in the normal manner. To retrieve the bit segments 22, the tool 20 is relowered into the drill and then withdrawn a short distance to retract the insert 24 so that the bit segments 22 collapse back onto the cradle 176 and can then be withdrawn from the drill 12.

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First Claim