Different Methods of Tightening Flange Locknuts

Flange locknuts are all-metal prevailing torque locknuts that have a large circular bottom with top hex section. As with all torque locknuts, flange locknuts prevent free-spinning and require torque and tension to tighten them.

With threaded internal structure, they create frictional interference when you tighten them over any surface. They can be used in different applications like truck manufacturing, lawn and garden equipment, wood and plastic surfaces, and more. However, they must be clamped properly to prevent insufficient clump load, damages, and loosening in the future. There are different methods of tightening these fasteners and you must know them for proper application.

Flange Locknuts

1. Torque Control Tightening

It is the most popular way of tightening torque prevailing locknuts. Torque is the maximum rotational force that can be used to tightly put a locknut in its place. For applications where you need strong tightening, you must use maximum torque. If you apply too high torque on the flange locknut, the nut may break. Therefore, it is necessary to understand the torque limits for tightening such locknuts.

Torque is often applied to overcome friction created between the two mated surfaces. Nominal torque for a locknut is often provided by the locknut supplier but it can also be calculated by using the relationship between torque and the resulting tension. With slight variations in the frictional conditions, torque-tension value changes drastically. It is important to use coated flange locknuts and the torque value mentioned by your locknut supplier to prevent failures.

2. Torque + Angle Control Tightening

Some flange locknuts come with torque + angle tightening specifications. In this method, the locknut is tightened first using torque and then the specific angle is used to tighten it further. Since flange locknuts can be reused for a limited number of times, determining that specific angle is very crucial. The angle is relative to the mating fastener and must be specified by your supplier.

3. Torque + Angle + Yield Control Tightening


This tightening method is used in critical application such as cylinder heads. It helps to achieve high preloads as it minimizes the influence of friction between two mating surfaces. Flange locknuts with torque + angle + yield control tightening specifications are tightened in the same way as in torque plus angle locknuts but the craftsman has to use his skill to determine the yield point for the best precision.

Flange locknuts come in two forms – serrated and non-serrated. Clamping serrated and non-serrated flange locknuts require different approaches. When you use serrated flange locknuts, they displace material on the clamped surface. You must work with your locknut supplier to determine which tightening method you should use for your specific purpose to avoid damages both to the flange locknut and the mating surface.