Definition
Tool Joint — A tool joint is the heavy, threaded forged connection welded to each end of a drill pipe tube — a pin on one end, a box on the other — that lets joints be screwed together into a drill string and carries the make-up torque.
Also known as: tool joints, drill pipe tool joint
What a tool joint does
A tool joint is the connection at each end of a joint of drill pipe. Unlike the thin-walled tube body, the tool joint is a thick, forged and heat-treated steel component with a coarse, tapered rotary-shouldered thread. One end is machined as a pin (external thread) and the other as a box (internal thread), so consecutive joints thread together into a continuous string.
Tool joints are friction-welded to the upset ends of the drill pipe tube and then hardbanded to resist wear against the casing and open hole. They must carry the full torsional, tensile and bending loads applied to the string while maintaining a pressure-tight seal at the shoulder.
Key features
- Rotary-shouldered connection — the seal and torque are carried on the shoulder, not the threads.
- Hardbanding — a wear-resistant weld overlay on the box (and sometimes pin) that protects the tool joint and casing.
- Make-up torque — each connection has a recommended torque range that must be applied for the shoulder to seal and the connection to survive downhole loads.
Why it matters for rentals
Tool-joint condition drives the inspection class of rental drill pipe. During inspection the connections are gauged dimensionally and checked by magnetic particle inspection (MPI) for cracks; worn or damaged tool joints are recut or the joint is downgraded. When you rent drill pipe, the tool-joint type (for example NC50 or a premium double-shoulder connection) determines what it will make up against in your string.
Renting drill pipe with the correct tool-joint connection and inspection class is essential to a reliable string. If you’re unsure which connection you need, send us your specs and we’ll confirm compatibility.