A bead of paint or lacquer laid across the fastener and the surface beside it after final tightening. It confirms the fastener was checked, and a cracked or offset stripe shows at a glance that the nut has turned or the joint has slipped. It is standard practice on aircraft, rail equipment, wind turbines and heavy machinery, often in a brittle, tamper-evident lacquer.
Torque stripe on the brake line nut is cracked and walked off, somebody's had it apart, recheck it before it flies.
Also heard as
- torque seal
- witness mark
- torque paint
- slip mark
Related terms
Self-loosening
A tightened nut or bolt turning loose by itself, usually because sideways slip in the joint lets it walk off.
Click wrench
Shop name for an adjustable torque wrench that clicks and briefly gives way when the set torque is reached.
Breakaway torque
The torque needed to start a tightened fastener turning again, used to audit joints and rate locking features.