Flange Hex Locknuts vs. Hex Locknuts – Benefits of the Flange

In the vast majority of threaded fastener applications, there are valid reasons for opting for nuts or locknuts with flanges instead of using the “un-flanged” nut with a washer. If the application calls for a deflected-thread all-metal locknut, there are additional reasons. This blog entry will identify those reasons and provide supporting arguments. READ MORE

Torque-Tension Repeatability of Prevailing Torque Locknuts

For prevailing torque locknut applications where assembly and in-service performance are critical, it becomes appropriate to enhance the requirements and qualification tests of the locknut, beyond what may be called for in a consensus locknut standard. One common requirement enhancement is Torque-Tension Repeatability. Though the concept of this performance metric is easy to understand, defining limits that relate to the success of an application is as difficult as it is important. READ MORE

Prevailing Torque Locknuts - What Zinc Flake Coatings Do to Prevailing Torque

Since RoHS became effective in the European Union in 2006, there has been a global push to eliminate Cadmium (among other substances) from use in fasteners. Cadmium plating provides a level of lubricity that helps prevent galling in all-metal locknuts, and contributes to a more consistent torque tension characteristic in threaded assemblies... READ MORE

Prevailing Torque Locknuts - Nylon Insert Locknuts

The prevailing torque is developed when the male (bolt) thread interferes with the nylon ring and forms the complimentary female thread into the ring with a combination of elastic and plastic deformation. The outside diameter of the ring is constrained, so the inside diameter must allow this deformation without overfilling the mating thread, or the ring can be pushed out of the nut... READ MORE

Prevailing Torque Locknuts - When They Don't Work, What Happened?

You can't be in the locknut business very long without encountering someone having problems with locknuts in their applications. When a locknut manufacturer's registered quality system includes rigorous quality controls, their parts pass the qualification tests, and there are still problems on the customer's assembly line, what happened? The short answer is that sometimes there are misapplications of locknuts... READ MORE

Prevailing Torque Locknuts - How They Work

Localized plastic deformation - Some of the starting threads need to be able to accept the mating part (bolt, say) before the prevailing torque begins. The interference is therefore localized to not include the immediate start of the assembly. For nylon insert locknuts, the interference is only in the nylon ring, and the metal part of the nut is free-spinning... READ MORE

Prevailing Torque Locknut Testing and Qualification

In addition to inspections common to all internally threaded fasteners (nuts), prevailing torque locknuts are inspected for prevailing torque performance. Prevailing torque is the resistance to assembling or disassembling the locknut and mating part when the assembly is not clamping (not developing tension in the mating part)... READ MORE

Prevailing Torque Locknuts - What to ask for (Part 2)

Sometimes there is no standard locknut that will satisfy the requirements of an application. In these instances, a locknut fulfilling special requirements should be defined in a controlled document that specifies the characteristics listed in Part 1. That requirements document (an engineering drawing, for example) should reference standards for as many characteristics as possible.... READ MORE

Prevailing Torque Locknuts - What to ask for (Part 1)

There are several characteristics of prevailing torque locknuts that should be included in a complete specification. For many of these characteristics, it is equally important to define how the characteristic is measured... READ MORE