Definition
Tool Joint Upset — A tool joint upset is the thickened, forged transition at each end of a drill pipe tube where the wall is increased — internally, externally, or both — to provide the metal needed to weld on the tool joint and to reduce stress concentration.
Also known as: upset, pipe upset, IU, EU, IEU
What an upset is
A tool joint upset is the forged, thickened end of a drill pipe tube. The thin-walled tube body cannot support the coarse thread and welding of a tool joint, so each end is hot-forged to a greater wall thickness — the upset — providing a stronger cross-section to friction-weld the tool joint onto.
The upset also spreads the change in stiffness between the tube and the tool joint over a tapered length, reducing the stress concentration that drives fatigue at the pipe-to-tool-joint transition.
Upset types
- Internal Upset (IU) — wall thickened inward; keeps a uniform outside diameter.
- External Upset (EU) — wall thickened outward; keeps a uniform bore.
- Internal-External Upset (IEU) — thickened both ways, the most common for drill pipe, balancing strength and flow.
The upset type is matched to the connection: Internal Flush connections pair with internal upsets, while many modern connections use IEU pipe.
Why it matters for rentals
The upset region is a fatigue-critical zone that inspection watches closely. When you rent drill pipe, it is inspected to DS-1 in the slip and upset areas as well as the tube and connections — contact us to confirm the upset and connection you need.