Galling and Seizing
Galling and Seizing Questions
We get questions about galling or seizing. The customer’s complaint is that during installation the bolts are twisting off and/or the bolt’s threads are seizing to the nut’s thread. Often the customer thinks there is a quality issue. Leading the customer to believe this is a product quality issue. The problem is most likely “thread galling.” According to the Industrial Fastener Institute’s 6th Edition Standards Book: "Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing – the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out." |
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