Describes a fastener whose drive corners have deformed until a wrench, socket or key spins without gripping. Common causes are open-end or 12-point wrenches on tight fasteners, worn tools, inch and metric mix-ups, and corrosion that has thinned the flats. Recovery runs from a 6-point socket hammered on, to a twist socket or bolt extractor with spiral teeth, to welding a nut onto what is left.
Caliper bolt's rounded off, somebody went at it with a twelve-point, grab the extractor sockets.
Six-point sockets on anything tight, twelve-point only when access forces it; that habit saves most rounded heads.
Also heard as
- rounded
- chewed up
- stripped head
Related terms
Allen key
Shop name for an L-shaped hex key used to drive socket head cap screws and set screws.
Cam-out
The driver bit climbing out of a screw recess under torque, chewing up the recess and wearing the bit.
Easy-out
Shop name for a spiral screw extractor driven backward into a drilled broken bolt to unscrew it.
Rattle gun
Shop nickname for an impact wrench, from the hammering racket it makes running fasteners on and off.