Stainless Steel Fasteners locking up? It’s probably thread galling, not the quality of the parts but the common problem of using stainless steel fasteners.
The beneficial nature of using stainless steel is that it is corrosion resistant. This property is due to the fact that stainless steel, among other alloys, generate a protective oxide surface film. Though this is beneficial as it provides corrosion and rust resistance, it can sometimes lead to problems with installation.
Thread Galling occurs during fastener tightening and installation. When pressure builds between the contacting surfaces of the male and female threads, the protective oxides or coatings begin to shear, causing high points, or imperfections in the raw material to become locked together. The increase in friction causes the two parts to seize or “lock-up”. In serious cases, this problem is even referred to as “cold welding”, which illustrates the severity of the issue. Often, galling can cause damage to the thread of the fastener, but it can still be removed. In severe cases, the two materials completely weld together preventing loosening of the parts, and adding the difficult step of a forced removal and new parts to the process. The frustrating aspect of this is that both the nut and bolt can clear inspection individually, but fail to function effectively as a mechanical unit.
Though this problem may be frustrating, it is avoidable. The main issue to address is to decrease the friction between the adjoining parts. This can be done in several ways including a slower installation process (RPMs). The idea behind this method is to reduce the friction (and thus heat), between the parts preventing the “welding” process. Our recommended method, due to its ease of implementation, is lubrication. Common methods include specially designed lubricants and waxes, however due to its safety and ease of availability, we recommend dipping the bolt in Maalox.
Update: Maalox is no longer sold at stores so we started carrying an anti-seize solution that we’ve tested ourselves.
MRO Anti Seize solutions are tested lubricants with carefully manufactured specifications. Each type has unique characteristics which can be found on the individual product pages. We carry several different kinds of anti-seize to make sure we can offer a solution that works for you!
Anti-seize solutions offer many benefits to fastener installations. Not only do they provide fasteners with a layer of lubrication that reduces friction, the coating also creates an extra layer of lubrication and corrosion resistance to make your fastener assembly last even longer!
Other precautionary measures include using coarse threaded fasteners, using different grades of stainless steel for adjoining parts (take the corrosion resistance differences into consideration), and understanding the proper use of lock nuts. Because they are designed to add resistance to the existing threads of the bolt, it is best practice to make sure that a minimal amount of threads extend beyond the nut.
Reducing friction is the preemptive strike against this problem. That is why we recommend lubrication, and MRO anti-seize specifically, due to many of its properties beneficial to both sore stomachs and stainless steel. Galling can be a frustrating problem, but it can be prevented.
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