| 摘要 |
The invention provides a method of joining two rigid tubes such as are used in drill stems wherein a nipple internal to the tubes is threaded and screws into at least one of the tubes, the nipple provided with a zone of reduced internal diameter which registers with a cavity in the internal bore of the tube and the zone of reduced internal diameter expanded outwards into contact with the tube to occupy the registering cavity in the tube and form a positive lock against tensile forces. |
