Locking Nut Fundamentals
Ever found yourself asking the question "Which Locking Nut should I use for my project?"
In this video, we're taking a look at some of the most popular type of Locking Nuts in our engineering component range. We discuss the advantages and disadvantages of each type and talk about some examples of applications and industries they're used for. We also briefly discuss the problems that can occur when using Locking Nuts, such as Thread Galling, and tell you some of the most common ways to prevent these types of issues.
Locking Nuts can be used to help prevent some of the most common factors of loosening, such as shock and vibration.
Locking Nuts, also known as: lock nuts, prevailing torque nut, self-locking nut, stiff nut or elastic stop nut and they are almost always used in conjunction with a mating bolt to fasten components together. The two components are kept together by a combination of their threads' friction (with a slight elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together.
Avoiding Thread Galling When Using Locking Nuts
When using Locking Nuts, it’s important to ensure that the threads of the components are free from obstruction and as clean as possible to successfully fasten together. This will help to prevent issues such as cold-welding (also known as Thread Galling) which is where, owing to increased build up of friction during the installation process, the surface oxides begin to temporarily break down, with the pressure causing the two materials to bond together.
Galling is a type of adhesive wear and is particularly problematic if further pressure is continually applied to the fasteners. If this continues once galling has started to occur, this can cause the threads to seize together and strip from either the male or female threaded fastener. When selecting a locking nut, it is recommended that a different material or alloy is used, as this is one of the simplest ways to avoid thread galling.
What Are The Differences Between Each Type Of Locking Nut?
A hexagon nut is a standard fastener and one of the most basic fastening solutions. It's not technically a locking nut, but by using two nuts together (typically one standard hexagon nut and a thin hexagon nut) they act as a type of locknut, but have limited resistance to loosening under vibration. The thin nut is often referred to as a Jam Nut as it is ‘jammed up’ against the standard nut.
Nylon Locking Nuts
Nylon Locking Nuts are also very easy to install, but offer excellent resistance to loosening. The thread of the screw cuts into the nylon insert, then as this cools down, it contracts over the threads to lock into position.
A nylon locking nut is very difficult to remove after installation, but is vulnerable to high temperatures and certain chemicals.
Nylon locking nuts are available in various materials, such as stainless steel and aluminium. The nylon insert is available in different colours such as red, blue and grey. They are available in the following variations: nylon dome locking nuts, high nylon locking nuts and flanged nylon locking nuts.
Metal Locking Nuts
A metal locking nut is a basic but effective design, the triangular mark on its side is formed by a special stamping tool, which warps the top threads of the nut. This creates very tight threads which provide a locking mechanism, making it resistant to loosening.
These components are available in A2 and A4 stainless steel as well as Duplex stainless steel.
An aerotight nut is simple to install. The nut can be threaded onto the bolt by hand, but tooling is usually required for tightening.
The unique design and all metal construction of this nut makes it resistant to vibration, while also remaining resistant to temperatures and harsh chemicals.
The locking mechanism of an aerotight nut makes it reusable, and also allows it to be effective when not fully tightened.
A shear nut is a permanent fastening solution that is installed like a standard hexagon nut, and only requires a regular spanner to install.
Once the nut is tightened, the head can be sheared off by continuing to tighten the fastening.
This particular nut takes between 7 and 13 Newton Meters to shear. This type of locking nut is designed to be resistant to tampering, but does not offer significant vibration resistance.
Note: The bare metal left exposed by the shearing action is minimal, and the finish of the fastening is neat and tidy.
Alternative Locking/ Anti-Vibration Fastening Solutions
Other anti-vibration fasteners such as Locking Washers, including the popular Nord-Lock Washers, which feature an innovative wedge-locking solution, are also an option when attempting prevent self-loosening.
AccuLock Thread Locking Patches are another anti-vibration solution, designed to increase the friction between the threads of the fasteners, increasing effectiveness and longevity of the components and can help to reduce thread wear and galling.
For more information on locking nuts, check out our How To Use Locking Nuts video below. In the tutorial, we look at some of the applications and industries the components are used in, and discuss the advantages and disadvantages of our most popular types of locknuts.