Thread Galling Basics

Nuts and bolts are the most essential part of machinery design and assembly. Without fasteners, the most important structures of our daily lives would crumble. Therefore, the quality and application of nuts and bolts are of the utmost importance. And yet despite our advances over the years, fasteners are still issue prone. The biggest problem for hardware is thread galling. Learn all about this problem and how to solve it.

What is Thread Galling?

One of the most prevalent issues when installing fasteners is called thread galling (also known as cold welding). This is when the bolts are twisting off and the bolt’s threads are seizing to the nut’s thread. During the tightening process, pressure and friction build between the two surfaces. As a result, protective oxides are broken down and possibly wiped away. The high points between the two lock together, causing an increase in adhesion. In severe cases, thread galling leads to the actual freezing of threads together wherein if the tightening is continued, the fastener can be twisted or its thread can be ripped out altogether. Once thread galling has occurred, it’s nearly impossible to remove the fastener without cutting or splitting the nut.

Preventative Action

Obviously, thread galling is not ideal for such an important contribution to structures that make up our houses, bridges and garages. Luckily, there are several precautions you can take to prevent corrosion, galling, seizing and stripping of bolts and fittings during disassembly and reassembly.

Nut and Bolt Quality

Without quality fasteners, your constructions are not only prone to issues but, as a result, can create unsafe environments for everyone. Inferior nuts and bolts can lead to an onslaught of issues that can range from an annoyance to a safety hazard. Low-quality hardware breaks, rusts and cracks easier. It also deteriorates quicker, which results in increase costs due to a constant need for replacements. Purchasing high-quality fasteners will save time and money, both short term and long term.

In addition, make sure you perform a full quality check before installing new fasteners. Assess your products to ensure that they are clean and undamaged. Defects and debris can increase the possibility of thread galling. But with the right, high-quality fasteners, you can ensure dependable, safe performance.

Lubrication

Even with the best-made products, you can still run into some problems. Nuts and bolts experience regular friction, especially in large, steel structures. Lubricating the internal and external threads can help actively reduce the chance of thread galling. Anti-seize compounds can offer the lubrication needed to reduce friction and prolong your equipment’s life. These solutions can be applied at the point of assembly or pre-applied to eliminate future issues.

However, keep in mind that lubrication is not a one-size-fits-all. For example, stainless steel is a commonly used material for food-related structures, so certain lubricants could be harmful. Make sure to choose a food grade compound for applications involving incidental food contact. The same goes for various industries with particular conditions such as marine environments or high-temperature situations. Personalization will aid in preventing issues and improving efficiency.

Installation Speed

Heat and friction typically go hand-in-hand. As a result, temperature plays a huge role in the possibility of thread galling. As a precaution, try to slow down the installation of your nuts and bolts. Use hand-operated tools because the heat generated from power tools can increase your chances of galling. Keeping things cool by slowing down the installation process will reduce and sometimes even solve a thread galling problem completely.

Compatibility

In construction, there are countless components working together, so if one piece isn’t right, the integrity of the structure is at risk. Thread galling seems to be the most common with fasteners made of stainless steel, aluminum, titanium and other alloys. These materials produce an oxide surface film for protection against corrosion. However, during installation or use, this surface can wear away, putting the materials directly in contact with one another and causing friction-induced thread galling.

Be sure to consider the type of material used for your structural projects. For instance, you may want to consider using a different grade of stainless steel for your nuts and bolts if the same one hasn’t been successful. Find the specialized threaded nuts and bolts in the right size, finish and grade to ensure compatibility and effectiveness.

Stainless steel fasteners like nuts and bolts are prone to thread galling. However, by taking the necessary precaution and action you can prevent issues from arising and avoid further problems, costs and labor down the road.

Sources:

www.pencomsf.com/wp-content/uploads/2012/08/galling_stainless_steel_fasteners.pdf

http://www.estainlesssteel.com/gallingofstainless.html