Thread Galling

Many customers have made comments about stainless steel nuts and bolts locking up. This is known as 'thread galling' or 'cold welding'. It occurs in metals such as stainless steel, titanium and aluminium.

As a nut is tightened on a bolt, the thread surfaces slide against each other. As this happens the protective oxides that are on the surface of the metal can be damaged causing the nut to lock up on the bolt.

If it is tightened too far the nut may actually freeze on the bolt.

How to stop this from happening

Option 1: Lubricate the nuts and bolts using appropriate lubrication.

Option 2: Do not use an electric tool or a spanner straight away. If possible use your hand to put the nut on finger tight. If you feel the threads start to lock up then twist back half a turn and try again. Only use an electric tool or a spanner once you have the nut where you need it.

Option 3: Some people have recommended the use of different grades of stainless e.g. use an A4 stainless nut with an A2 stainless bolt. this may solve the problem as different grades of stainless will harden at different rates.