Hard Lock Nuts are innovatively designed to withstand loosening from vibration longer than any other fastener on the market. Ideal for critical mechanical applications, the Hard Lock ensures a secure connection for enhanced safety and reduced maintenance and inspection costs.
New to the U.S. market, and a leading choice for engineers in Japan, the United Kingdom and Europe, the Hard Lock Nut incorporates a unique wedge principle to create a powerful self-locking force. A small curve in the sliding part of the convex top of the lower nut acts as the wedge. When the concave upper nut is tightened, the effect produced is exactly the same as that produced by a hammer driving in a wedge. Because the Hard Lock Nut maintains the initial axial force, or tightening strength, it not only prevents screws from coming loose and bolts from breaking, but also dramatically cuts personnel and maintenance expenses, as well as costs related to claims that can seriously threaten a company.
 
Hard Lock Nuts have been proven effective in a variety of tests. Passing the American Vibration and Impact Test NAS 3350/NAS 3354 (National Aerospace Standard) by a substantial margin, these nuts outlasted nylon nuts, nuts with tongued washers, double nuts and many other specialty lock nuts by up to three times. Hard Lock Nuts also retained their grip longer than competitor versions in a series of Junker Horizontal Screw Looseness Tests. These studies, as well as Tensile Strength and Torque / Axial Force Tests confirm that Hard Lock Nuts maintain a stable tightened condition, regardless of the type of impact to which they are exposed. Even when loosened by 45 degrees, more than half of the tightening torque remained. What’s more, when a vibration test was performed in this condition, no loosening occurred, indicating that a self-locking effect is present even if the nut is not fully tightened.
Hard Lock Nuts are ideal for use in aircraft, automotive and construction applications. They are available in a variety of materials with a range of surface treatments to meet the needs of varying applications. Shapes include standard, semi-thin, thin and round, with custom shapes available as an option. Semi-thin and thin Hard Lock Nuts are also available.

The two-piece Hard Lock Nut is easy to install, requiring only the use of a wrench. Because there is no abrasion between the concave and convex, the nut is reusable.