Benefits of Thread Rolling

Do you need precision threaded components for critical applications in the aerospace industry (e.g. fasteners, aerospace bolts, nuts, screws)? 

If you are used to choosing thread cutting for critical components, you should be aware that these components have a much higher failure rate in destructive laboratory tests than rolled threads. This is because only a thread rolling service can provide the excellent tensile, shear and fatigue strength your components require. 

Thread cutting vs thread rolling 

Thread cutting involves physically cutting the part to remove material, which can weaken the structural integrity of the component. Thread rolling, on the other hand, is a cold forging process that actually changes (and strengthens) the physical properties of the material without removing any material.

Sharp Tail Screw Die

The procedure replaces the malleable material of the component with a hardened steel die formed to specification. Unlike the weakening effect produced by removing material during thread cutting, thread rolling actually moves molecules into the thread form. This results in a denser thread and thus improved quality and strength. As an added benefit, polishing the steel tooling used for thread rolling produces an excellent micro finish, which reduces wear and further extends component life. 

Benefits of thread rolling 

The benefits of thread rolling include 

Quality of finish. Thread cutting often leaves cut marks and tool lines, producing a rough surface and fragile threads that are prone to breakage. Thread rolling, however, leaves parts smooth and strong, eliminating the need for secondary polishing and finishing operations. 

Speed. Thread rolling machines can run more than three times faster than thread cutting machines, which can significantly reduce lead times.

Self Drilling Screw Dies

Strength. Thread rolling increases the tensile strength of the part due to material compaction and work hardening. The displaced material forms dense layers which are packed tightly together to form a stronger thread. In thread rolling, there are two main forms of thread that provide different levels of strength. 

Basic Uniform National Threads (UNR classification). These standard threads are typically used in commercial applications where strength is important but safety is not necessarily a critical factor.

J-shaped threads (UNJC or UNJF). These threads have a large root radius and will produce a very strong thread when rolled. They are ideally suited to critical applications where people's lives depend on their functionality. J-threads can be found in most aerospace applications. 

Tool life. Cutting tools are known to wear easily, but a set of precision rolling dies can roll thousands of precision threaded parts without any problems.

Combined centreless grinding and thread rolling for internal quality and testing

In all cases where threaded aerospace components are rolled rather than cut, a higher percentage of threaded aerospace components will pass destructive laboratory testing.

The process involves cutting the threads transversely to view their cross-sectional views, then mounting them in wax, polishing them and etching them in solution to examine them under a microscope at over 500x. We check for fatigue, material flow, density, cracks, laps caused by excessive rolling and any thread defects that are not visible on the surface. 

Send them to Fengfeng Moulds for a professional thread rolling service. Contact us today for a free estimate!