Thread Galling: Why Stainless Steel Fasteners Seize and How to Prevent It
November 5, 2026
Thread galling can cause stainless steel nuts and bolts to seize during installation. Learn what causes it, which factors increase
Thread galling can cause stainless steel nuts and bolts to seize during installation. Learn what causes it, which factors increase
Discover how flange nuts distribute clamping force, simplify assembly and protect mating surfaces, plus when to choose them over a
Nyloc nuts provide a simple and compact method of resisting unwanted loosening, making them widely used across automotive, machinery, equipment
When a bolted connection is exposed to constant movement, vibration or heavy loads, preventing the nut from loosening becomes critical.
Stainless steel fasteners are widely used for their corrosion resistance, durability and suitability for demanding environments. However, even high-quality stainless steel nuts and bolts can experience a frustrating problem during installation: thread galling.
Understanding what causes galling, why stainless steel is particularly susceptible and how to prevent it can help avoid damaged fasteners, costly replacements and unnecessary downtime.
Thread galling is a form of adhesive wear that occurs when two metal surfaces slide against each other under pressure.
During tightening, microscopic areas of the mating threads can adhere to one another. As the nut continues to turn, these connections tear apart, damaging the thread surfaces and transferring material between them.
As the damage progresses, friction increases and the fastener may become increasingly difficult to turn. In severe cases, the nut and bolt can seize completely, making removal difficult without damaging or destroying the fastener.
Although stainless steel offers excellent corrosion resistance, certain grades, particularly austenitic stainless steels such as 304 and 316, are susceptible to galling.
Stainless steel forms a thin protective oxide layer that helps prevent corrosion. During tightening, friction and contact pressure can disrupt this layer, exposing fresh metal surfaces that may adhere to one another.
This is particularly relevant when similar stainless steel materials are used together, such as a stainless steel nut and bolt of the same grade.
Importantly, thread galling is not the same as corrosion. It is a mechanical wear process that can occur even when the fasteners are completely clean and free from rust.
Several installation and material factors can increase the likelihood of galling:
1. High tightening speeds
Rapid tightening, particularly with powered tools, can increase frictional heating and the risk of adhesive wear.
2. Inadequate lubrication
Dry metal-to-metal contact increases friction between mating threads, making adhesion and surface damage more likely.
3. Damaged or contaminated threads
Burrs, debris, poor thread finishes and existing damage can create localised areas of high contact pressure.
4. Unsuitable fastener combinations
Certain combinations of similar materials and hardness levels may be more susceptible to galling than appropriately selected alternatives.
While galling cannot always be eliminated, correct fastener selection and installation practices can significantly reduce the risk.
Use a suitable anti-seize lubricant.
An appropriate lubricant can reduce friction and direct metal-to-metal contact. Always check that the product is compatible with the fastener material, operating environment and application.
Control tightening speed.
Slower, controlled tightening can help reduce the likelihood of galling. Avoid unnecessarily high-speed installation, particularly when working with stainless steel fasteners.
Inspect threads before assembly.
Ensure nuts and bolts are clean, undamaged and correctly matched. Never force a fastener that is cross-threaded or unusually difficult to turn.
Select suitable fastener materials.
Where galling is a concern, alternative stainless steel grades, compatible material combinations or specialised thread treatments may be appropriate, provided they meet the application’s mechanical and corrosion-resistance requirements.
Follow the correct tightening specifications.
Lubrication changes the relationship between applied torque and bolt preload. A torque value intended for dry threads may produce excessive clamp load when applied to lubricated threads.
Always follow the manufacturer’s specifications or an appropriately engineered tightening procedure for the actual fastener and lubrication conditions.
Thread galling highlights why fastener selection involves more than choosing the correct diameter, length and material.
Understanding how different fasteners behave during installation and operation helps reduce avoidable failures and keeps projects moving.
At Bolt & Nut Centre, we understand the importance of selecting fastening solutions suited to the application. Whether you’re working with stainless steel fasteners or other industrial fastening requirements, our team can help you explore suitable product options.
Visit www.boltandnut.co.za or contact us on 033 342 1470.
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