How to Install a Locknut: A Straightforward Guide

For over 40 years, Lok-Mor has helped engineers and manufacturers secure critical joints in some of the world’s toughest environments. One of the most frequent questions we receive is how to properly install different types of locknuts.

While each of our 18 locknut styles has unique features, the installation process generally falls into three straightforward categories.

Here is our expert guide to installing your locknuts correctly:

Installing Free-Spinning Locknuts 

Free-spinning locknuts are designed for speed and ease of use. These nuts turn freely on the bolt threads until they are firmly seated against the base surface.

• Step 1: Threading. Manually spin the locknut onto the bolt until it makes contact with the bearing surface.
• Step 2: Seating. Use an appropriate wrench to tighten the nut until it is firmly seated against the base.
• Step 3: Locking. Apply the final specified torque, which varies by design. For designs like the DBL-LOC®, this final tightening deforms the nylon insert in the nut to create a seal around the threads. For the SPN-LOC®, this step engages serrated elements that bite into the mating surface to prevent loosening.

Unsure if you’re working with a free-spinning locknut? Read our blog on free-spinning locknuts or browse our free-spinning collection.

Installing Prevailing-Torque Locknuts

Unlike free-spinning types, prevailing-torque locknuts provide constant frictional resistance the moment the locking element engages the bolt threads.

• Step 1: Engagement. Manually thread the nut onto the bolt. You will feel resistance as soon as the deflected threads or nylon meet the bolt.
• Step 2: Tightening. Continue tightening with a wrench. Because these nuts are “self-locking” through thread interference, you will need tools for the entire installation process.
• Step 3: Final Seating. Ensure the nut is firmly seated. The deformation of the locking element (such as the collar on a C-LOC™) provides a secure, maintenance-free connection.

For more information on prevailing-torque locknuts and how they work, read our blog on the subject or see our complete prevailing-torque collection.

Mechanical Precision: Pin and Key Locknuts 

For applications where structural integrity or permanent security is the highest priority, we offer specialized mechanical locking designs.

The ANCO® PN-LOC® (Structural Pin)

Our award-winning flagship product, the ANCO® PN-LOC® is the industry standard for structural integrity. To install, thread the nut onto the bolt like a standard heavy hex nut. As you tighten it, the stainless-steel ratchet pin slides over the threads and engages with a unique controlled-lock indentation. This provides a consistent locking torque for a permanent lock.

The KEY-LOC™ (Security Key)

When your assembly must be permanent and tamper-resistant, the KEY-LOC™ is the answer. This nut installs as a free-spinning fastener until it is firmly seated against the base. Once seated, you activate the “locking key” mechanism by striking it with a hammer. Once this key is engaged, the nut becomes non-reversible and cannot be removed, deterring unauthorized disassembly.

Installing Two-Piece Locknuts

Specialized high-vibration applications may require two-piece locknuts like the DRAKE™. As the name implies, these locknuts come in two pieces, a top nut and a bottom nut. This allows two-piece locknuts to be positioned anywhere along the threaded section for a versatile, vibration-resistant solution.

To install, first secure the bottom nut to reach the required clamping load. Then, thread the top nut onto the bottom nut and tighten it firmly. This creates a powerful “wedging action” that ensures a positive lock without damaging mating threads.

Made in America. Made Right.™

Every Lok-Mor locknut is manufactured, locked, and tested at our state-of-the-art, A2LA-accredited lab in Mansfield, Texas. Whether you need 100% domestic quality or custom-manufactured locknuts, our expertise ensures your joints stay secure under any condition.

Need technical specs or a custom quote? Contact a Lok-Mor expert today by emailing us at [email protected] or filling out our contact form.