The Evolution & Use of Metric Kep Nuts

Some things have been around so long that it’s easy to forget that there was a time they didn’t exist. These items fill their need so easily and so completely that we can’t imagine a time when people had to get by using other means. One of these items is the “kep” nut. This nut has been around for nearly a century, and many assemblers couldn’t imagine life without it.

metric kep nutsA Little History
The kep nut was invented in 1923 by Shakeproof Screw and Nut Lock Company. The “kep” in kep-nut comes from the name Sha(kep)roof. Now owned by Illinois Tool Works (ITW), the kep nut revolutionized manufacturing and assembly just as assembly lines were taking off.

Before the kep nut, washers would be placed on bolts before nuts were placed on threaded fasteners by hand. In the high-paced environment of an assembly line, some washers were invariably omitted. That resulted in assembly failures and jeopardized emerging industries. That is when Shakeproof and ITW came in.

Acquisition and Growth
ITW made Shakeproof their first acquisition based on the strength of the kep-nut design. With its integrated washer, the kep nut eliminated the need for hand assembly. Large numbers of nuts could be installed rapidly, without the risk of forgetting a washer or fumbling to put one on. This increased both the speed and the quality of the assembly line, assuring its place in manufacturing history.

Metric Kep Nuts 4Metric Kep Nuts in Action
The toothed design of the washer provides a firm grip on the mating surface, preventing loosening of the bolt during use—hence the name “Shakeproof.” The toothed washer spins independently of the nut, allowing the teeth to bite into the mating surface at a single point. Pressure from the nut then drives the teeth deep into the mating surface, making for a secure assembly.

Kep Nuts Today
While the “kep nut” name is a trademark of Illinois Tool Works, the name has become synonymous with any nut that features a free-spinning attached washer. Metric kep nuts are in use in every manufacturing industry, and are used to assemble just about anything imaginable. From washing machines to space shuttles, these nuts are used everywhere in and out of this world.

Similar to their advantages in 1923, today the metric kep nut:

  • Boosts the speed and efficiency of assembly processes.
  • Eliminates the need to slip the washer into place by hand.
  • Simplifies your inventory by combining two in one.

The Metric Kep Nut You Need
At Mr. Metric, we carry kep nuts in a variety of styles and materials. Whatever you’re trying to put together, Mr. Metric has the metric kep nuts you need to keep it together.

Contact us for help finding the metric kep nuts you need to ensure your assemblies stay assembled.


About the author

Mr. Metric is the spokesperson for, an online store for metric fasteners. Get $7.50 flat shipping with no minimum orders, plus advice and best practices for using metric fasteners in any application.

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