Severe adhesive wear in which the protective oxide films on mating threads break down under pressure and sliding, so the metals bond and tear. Stainless steel, aluminum and titanium are the usual victims, and fast installation with power tools makes it worse by heating the threads. Prevention includes anti-seize, slower rundown speed, coarse threads and pairing different alloys or hardnesses.
Nut galled halfway down the stainless rod, it's welded on, cut it off and get anti-seize on the next one.
Slow the tool down; most stainless galling on a line starts with a power driver spinning the nut too fast.
Also heard as
- gall
- galled
- thread seizure
- cold welding
Related terms
Anti-seize
A grease loaded with metal or ceramic particles that stops threads from galling, rusting or bonding under heat.
18-8 stainless
Fastener shorthand for austenitic 300-series stainless, about 18 percent chromium and 8 percent nickel.
UNF
Unified National Fine: the inch thread series with more threads per inch, such as 1/4-28, 3/8-24 and 1/2-20.
Helical insert
A coil of diamond-section wire screwed into an oversize tapped hole to repair a stripped thread or armor a soft one.