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Thread Galling: How it Happens and How to Avoid it

Thread Galling: How it Happens and How to Avoid it

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Thread Galling is a very common problem in most repair projects and it’s important to be mindful of this when using locking nuts. Broken thread caused by fused metals is most often seen with materials like stainless steel, aluminum, and titanium. While on the other hand, hardened steel bolts, especially those that are zinc plated, are safer. Check out how this problem can happen and how you can avoid repairing threads damaged by bonding before they even occur.

So how does Thread Galling happen?

Thread Galling or also called “cold welding” happens when there is too much pressure and friction on installation of bolts and nuts that causes the materials to seize together making it almost impossible to fix a thread or remove them from one another without having to either cut the bolt or split the nut. This situation is really common where there is not enough lubrication between the surfaces. Sometimes, as a material galls, some of its parts are pulled with the contacting surface, particularly if there is a huge amount of force compressing the surfaces together. It appears as if parts of the bolts or nuts have been torn out or forcibly removed and the torn lumps of the removed material will be visible. Fasteners that have fine patterns are more open to having a broken thread. Another characteristic that promotes metals welding together is because some materials are ductile and have crystal structure that enhances cohesive attraction. So when friction, ductility and cohesion are all existing together, cold welding has a high chance of happening. But the good news is that this could be avoided with proper maintenance! 

So here’s how you can avoid this

  1. Lubricate! Use anti-seize or anti-cold welding lubricant to clean the material before starting the installation. This is the most effective way to avoid repairing threads caused by metal bonding. 
  2. Slow down your installation speed. The installation process can increase heat and build up of friction. So make sure to tame your speed to allow the heat to cool down. It is suggested to not use power tools for installation to prevent the need to fix a thread in the future, especially for stainless steels and other fastener materials that are prone to this problem.
  3. Use two different material types. If applicable in your situation, use one softer grade material and one harder grade material for installation to avoid having too much pressure on the surface and surely prevent metals sticking together.
  4. STOP when a fastener begins to bind. When you see that the fastener is beginning to bind before you are actually tightening it down, STOP for a moment. You wouldn’t want to push this through because it can get tough when fixing threads damaged caused by galling. Just wait for a minute or two to allow any heat to dissipate before you can take the fastener off. Check if there is any damage that occurred and then if everything’s clear, try again with a new nut.
  5. No prior damage. Make sure that the teeth of the fasteners have no prior issues before proceeding with the installation. Prior damaged thread can increase friction that will bring more problems. So better fix those initial stripped grooves in seconds using our thread repair kit and proceed to the installation afterwards.
  6. Controlled Environment. As we mentioned, too much heat can cause the grooves on the bolt to weld together so try to keep your fasteners in a cool and controlled place. Don’t leave them in the sun or in a hot room for too long to avoid increasing the chance of cold welding.
  7. Bolts with Fewer Grooves. While bolts with fine grooves are awesome tools, because of its design, it normally needs to have many more turns per inch. This results in producing greater friction per inch. So if possible, use coarse bolts with fewer grooves.
  8. Installing Under Load. When tightening a nut onto a bolt, a broken thread may occur if there is increased load because it will force the materials to push against each other during the installation process. So make sure that there is no to minimal load in the assembly.
  9. Extra Care. When you are using locking nuts, especially nylon lock nuts, this tool is prone to generating higher heat and friction during installation so extra care is a must. Always remember to not rush the process and slow down so you won’t have any bigger problems.

Use these tips to avoid thread galling and always remember that if you need to repair a thread, you can always count on our thread repair kit to fix the problem in seconds. It is the only US Patented and Engineered tool you will ever need to fix inside and outside threads of any kind. Rotary Thread will restore any thread galling on stuck bolts and nuts in a bind. 

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