How to Prevent Thread Galling When Using Stainless Steel Fasteners

Stainless steel fasteners are durable and can serve you for years with low maintenance. However, during installation, these fasteners may be affected by thread galling which is an incident that causes nuts and bolts to seize up because of friction and pressure. The seizing up causes the fastener to attach permanently to the bolt, forcing you to cut the lock to separate it from the nut. Fasteners that have threads are susceptible to galling. Even though thread galling is a typical process, you can adopt simple tricks to reduce or eliminate the phenomenon. Here are a few aspects that beginners need to know about galling in stainless fasteners and how to prevent the same from happening to your stainless manufacturing:

How Thread Galling Occurs --Thread galling occurs in metal fasteners such as titanium, aluminum, stainless steel, and other alloys that form an oxide film to protect the surface. When you tighten stainless steel fasteners, the pressure is generated between the sliding threads and the contacting threads. The pressure breaks down the oxide surface, leading to shearing, clogging, and locking action, which tightens the fastener to the bolt. Continued tightening of the fasteners might lead to ripping of threads and subsequent seizing up.

Lubrication -- Lubrication of external and internal threads of screws can reduce galling. Industry experts recommend that the lubricant should be high in inorganic compounds such as molybdenum disulfide. Such a compound is immune to the effect of oxygen and acids. Furthermore, the lubricant has little friction, and thus, suitable for eliminating thread galling. You can also consider using pressure waxes as an alternative for lubrication. When shopping for a premium product, go for an anti-seize lubricant.

Installation Speed -- High-speed installation of fasteners produces heat that causes friction. The friction is the main contributor to thread galling in stainless steel fasteners. Therefore, care should be taken to reduce the speed of installation, preferably by using hand tools as opposed to power tools.

Vary the Alloy Grades -- When you 'mate' a nut and bolt of the same alloy grade, the likelihood of thread galling rises significantly. A rule of thumb is to use components of different alloy grades. Different alloy grades have various work hardening properties. Work hardening refers to the hardness of metals, such as stainless, due to physical processes, including hammering, rolling or fastening. Therefore, if the fasteners are of different alloy grades, the work hardening process will occur at different rates, and hence, minimize the chances of seizing up of fasteners.