Home Galling Galling Developing a condition on the rubbing surface of one or both mating parts where excessive friction between high spots results in localized welding with substantial spalling and a further roughening of the surface. When it comes to threaded bolts, galling can lead to freezing of the threads; a further tightening force could shear off the head of the bolts or strip the treads. Galling can be avoided through proper lubrication (depending on the end application), lessening the tightening speed or using different metal alloys for the nut and bolt. < Glossary