RS PRO, M12, Plain Nylon Insert Lock Nut

  • RS Stock No. 521-973
  • Manufacturer RS PRO
Technical data sheets
Legislation and Compliance
RoHS Certificate of Compliance
COO (Country of Origin): CN
Product Details

A2 Stainless Steel - Metric

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

Features and Benefits

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

There are various metric sizes available:

521-917 is an M3 stainless steel self-locking nut • 521-923 is an M4 stainless steel self-locking nut
521-939 is an M5 stainless steel self-locking nut
521-945 is an M6 stainless steel self-locking nut
521-951 is an M8 stainless steel self-locking nut
521-967 is an M10 stainless steel self-locking nut
521-973 is an M12 stainless steel self-locking nut
275-692 is an M16 stainless steel self-locking nut
275-709 is an M20 stainless steel self-locking nut

How to tighten a 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.

How many times can a self-locking nut be used?

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.

Attribute Value
Thread Size M12
Type Nylon Insert
Stainless Steel Type A2 304
Finish Plain
5 : Next working day (AU stock)
33 : 5 working days (Global stock)
Price (ex. GST) 1 Bag of 100
$ 106.85
(exc. GST)
$ 117.53
(inc. GST)
Per Bag
Per unit*
1 - 4
5 - 9
10 - 29
30 +
*price indicative
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