Back-off sub is also called back off spear. It can instead of taper tap to fish or back off when dealing with sticking. If the fish stuck or can’t be back off sub, and then trip the drilling tool.
Specification
Model | OD mm(inch) | Conn. | ID mm(inch) | OAL mm(inch) |
ZDK105 | 105(4 1/8) | NC31B LH x NC31P | 15(19/32) | 580(22 13/16) |
ZDK121 | 121(4 3/4) | NC38B LH x NC38P | 22(57/64) | 628(24 3/4) |
ZDK165 | 165(6 1/2) | NC50B LH x NC50P | 28(1 1/8) | 690(27 3/16) |
ZDK178 | 178(7) | 6 58REGB LH x 6 5/8REP | 28(1 1/8) | 700(27 9/16) |
ZDK203 | 203(8) | 6 58REGB LH × 6 5/8REP | 35(1 3/8) | 723(28 1/2) |