How to Use Lock Nuts: A Guide
Using a lock nut is pretty straightforward; all you need to do is place it against the threaded end of the bolt, fasten it in place, and actuate its locking mechanism. However, not all locking mechanisms are the same, and in this article, we’ll discuss how to use lock nuts.
How Does a Locking Nut Work?
All locking nuts share one common functionality, to prevent, or at least minimize, the chance of accidental unfastening due to vibrations or external forces. However, each locking nut type has a different locking mechanism, and this functions slightly differently.
Nylon Insert Lock Nut
Nylon insert lock nuts are threaded fasteners that have a nylon insert on one end of their threads. When they’re fastened onto the bolt’s threaded shaft, the bolt passes through the unthreaded nylon and displaces it within the nut. The displaced nylon exerts pressure onto the threads, preventing vibrations and accidental unfastening.
Unlike standard hex nuts, these self-locking nuts are nearly impossible to screw onto a bolt by hand. Instead, you’ll have to rely on tools, such as a wrench or a spanner, to fasten the nylon insert nut into place.
Jam Nut
Jam nuts work just like typical hex nuts; you can easily fasten them onto a bolt by hand, but further fastening or tightening would require hand tools. These are used in conjunction with one another; simply fasten the first jam nut and secure it using the appropriate hand tool.
Next, fasten the second jam nut over the first one, and secure it in place. The nuts are jammed against each other, bearing in the opposite direction, and when the thread in the jam nut moves as a result, the two nuts provide a clamping force. You can use two jam nuts with one another or one standard and one jam nut.
Castellated Nuts
The castle nut, or castellated nut, is typically used with a bore that has a pre-drilled through-hole. Once the nut is fastened, it’s further secured by slotting a cotter pin between the notches in the nut and the through-hole in the bolt.
The pin’s tines are then bent backward, preventing the nut from turning. Unfortunately, these aren’t really adjustable once fastened, so they’re best used for low-torque applications such as the automotive and aerospace industries.
Stover Nuts
Stover nuts, also called prevailing torque lock nuts, rely on a distorted thread located in the conical end of the nut and the prevailing torque. The prevailing torque refers to the tongue necessary to overcome the distorted mating threads within the cones that perform the locking action.
The cones provide orientation during automated assembly. They come in flanged or unflanged varieties; the flanged variety offers more security. These metal lock nuts are adjustable, which also makes them reusable, at least to an extent.
How to Tighten a Lock Nut
Tightening a lock nut is pretty much the same as with standard nuts and bolts, with the added step of securing the locking nut. Place a spring washer or a split lock washer onto the bolt, and fasten the nut using spanners, torque wrenches, and ratchets to secure the nut in place, and actuate its locking mechanism if necessary.
Securing Lock Nuts
Using lock nuts is really easy as long as you know which type of nut you’re fastening. If you want to learn more about various types of lock nuts, visit our engineering resources and check out our library of downloadable materials.