Throw away those nuisance locking washers – for ever!

1 min read

Thread locking nuts have been around for many years and generally offer very good results. However they have two significant drawbacks. First of all they are normally of the prevailing torque type which operate by putting a constant drag on the mating screw as it rotates to clamp the components together.This makes both starting the screw and then tightening it slower, more difficult and generally unsuited to power tools. Prevailing torque threads are also unsuited to setting with a predetermined torque setting or checking with a torque testing tool.

Secondly prevailing torque locking threads tend to become ineffective relatively quickly making them unsuited to any application where repeated removal of the screw might be required such as in an access panel for instance.

S-RT® nuts from PEM use a completely different system to create a thread lock which means that the mating screw can be spun in entirely without resistance until a clamp load is applied. Once suitably tightened a vibration resistant joint is created without the use of additional locking washers or messy thread locking compounds. Even better the screw can be removed and the nut reused as often as required without any loss in thread locking performance.

Screws can be installed using powered screw drivers set to a suitable torque load to ensure that all mating screws are tightened to a consistent load.

PEM S-RT® nuts are physically the same dimensions as standard S-Nuts and install into the same size holes using the same tooling. This means the change to thread locking nuts can be implemented seamlessly without any changes to components being required.

S-RT® nuts are currently available in M3 to M6 metric thread sizes and unified sizes 4-40 to 5/16-18

If you would like to know more about S-RT® self-locking nuts please call on 0808 123 1221 or email

About Zygology Ltd
With 40 years of experience Zygology is the country's largest distributor for POP Avdel and Southco; and main distributor for Penn Engineering in the UK. We are in addition the UK distribution hub for Masterfix fasteners and tooling. Zygology has also recently been appointed as an official distributor for Tesa assembly adhesive tapes. We have in-house repair facilities for POP Avdel and Masterfix tools. Zygology Ltd has an in depth knowledge of the products we sell and how they can be best incorporated into yours. We will always give the best advice we can - even if this sometimes means that we end up recommending a competing technology. We combine friendly service with competitive prices and excellent stock availability.