RS PRO, Plain Lock Nut, DIN 985, M20

Self-locking nuts with glass-filled nylon inserts. These are designed to remain secure despite conditions of severe vibration.

To DIN985
A2 grade 18//8 stainless steel (Type 304 S15)

Unlike conventional fasteners, lock nuts, sometimes known as self-locking nuts, contain a plastic insert that deforms to the thread of the fastener and prevents loosening without the aid lock threading adhesive. As such, they are often used where security in fastening is required. They are useful when joining soft materials such as wood and plastics where high surface pressure might damage the material, or when there is a short clamp load. However, their principal advantage is in applications where there is a high degree of vibration. Locking nuts resist loosening over time in dynamic load conditions. As such they are often used in;

• Domestic appliances such as washers and dryers
• Industrial machinery
• Automotive industry

• 521-917 is an M3 stainless steel self-locking nut

Locknuts can be applied in much the same way as conventional nuts. It is recommended to finger tighten as much as possible, and then tighten with an appropriate tool until the required torque is reached.

While a locking nut can be removed in much the same way a conventional nut can, their nylon inserts deform and degrade with each use. Therefore it is not recommended that self-locking nuts be re-used if it can be avoided, as their primary characteristic- the ability to dampen vibration and stress from dynamic loads- lessens in efficacy with each use.

RS PRO aims to be your go-to brand for reliability and value for money. We source great parts at great prices and test everything with our in-house experts to ensure the quality you need.

When it comes to tools and fasteners, we know that versatility and dependability are what you need. As such, we stock a variety of mainstay and specialist fasteners and couplers to suit any application. Whether you're a professional electrician, plumber, builder or DIY enthusiast, RS PRO is here to support you.