Mechanics and assemblers name threadlockers by color. Blue is the medium-strength grade that holds against vibration but lets a fastener come out with ordinary hand tools. Red is high strength and usually needs a torch or heat gun to release. Saying a bolt got red when it should have got blue is a common complaint in maintenance shops.
Put blue on the guard bolts, last guy used red and I had to torch every one of them.
Red on a small fastener can twist the bolt off before the threadlocker lets go, so size and strength must match.
Also heard as
- blue threadlocker
- medium-strength threadlocker
Related terms
Threadlocker
An anaerobic adhesive applied to fastener threads to stop them loosening from vibration.
Anaerobic adhesive
A one-part liquid that stays fluid in air but cures when sealed between metal surfaces away from oxygen.
Wicking
Describing very thin adhesives that run into already assembled joints by capillary action.
Glue
The everyday word for any adhesive, used freely on the floor but avoided in engineering drawings.