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API Standard back off sub
API Standard back-off sub
The back-off sub also named back-off spear. There is usually a left hand thread for tool joint at the upper part of the body, while the expansion sleeve has right hand thread. The guide cone at the lower part can make the expansion sleeve of the sub conveniently screw the fish connection. Raising the drilling tool, the expansion sleeve can hold the fish firmly, then reversing.
Specification
Type | OD (mm) | ID (mm) | Connection(API) | Thread for Fishing(API) | OAL (mm) |
ZDK105-1-00 | 105 | 20 | NC31 LH | 2 7/8EUE | 572 |
ZDK121-1-00 | 121 | 22 | NC38 LH | 3-1/2EUE | 600 |
ZDK121-2-00 | 121 | 22 | NC38 LH | NC38 | 630 |
ZKD159-1-00 | 159 | 28 | NC50 LH | NC50 | 690 |
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