Definition
Rotary-Shouldered Connection — A rotary-shouldered connection is a coarse, tapered threaded joint used on drill string tubulars in which a machined shoulder — not the threads — carries the make-up torque and forms the pressure seal.
Also known as: rotary shouldered connection, RSC, shouldered connection
How it works
A rotary-shouldered connection (RSC) is the standard threaded joint on drill pipe, drill collars, subs and most BHA components. It uses a coarse, tapered thread whose job is to draw the members together; the actual load-bearing and sealing happens where the flat shoulder of the pin meets the face of the box under make-up torque.
Because the shoulder carries the preload, the connection resists back-off, bending fatigue and internal pressure far better than a thread-sealed joint. Standard RSC families include API NC (Number Connection), Regular, Full Hole and Internal Flush, plus proprietary premium and double-shoulder designs.
Design features
- Single shoulder — one external shoulder on the pin, as in API NC and Regular connections.
- Double shoulder — a secondary internal shoulder that boosts torsional capacity, used in extended-reach and high-torque drilling.
- Stress relief — grooves and bore-back features reduce fatigue at the last engaged thread.
Renting the right connection
The RSC type governs what your tubulars make up against and their torque capacity. We rent drill pipe, drill collars and BHA components in standard and premium connections — contact us to confirm your string is compatible.