Types of Nuts and Their Features

Nuts are fasteners in the form of a metal block with a hole in the middle. This hole has an internal female thread, allowing the fastener to lock against the male thread of a bolt or screw. 

There are many types of nut designs for a range of applications. Take a look at this quick guide to the types we stock online at BOLTS.co.uk. 

Full Nuts 

Full nuts are usually hexagonal, and are the most common nuts used with bolts and set screws. 

Because of their popularity, they are available in a wide range of sizes and finishes, making them suitable for almost any and every project. 

Nyloc Nuts 

'Nyloc' is an abbreviation for nylon insert self-locking nut. 

The main feature of nyloc nuts is the nylon collar in the top portion of the nut that locks it in place by squeezing the threads of a bolt or screw as the nut is tightened. This creates friction, which prevents the nut from loosening. 

Nyloc nuts are reusable to an extent - their efficiency decreases with every use and they will, over time, become ineffective. 

Nyloc nuts can also be used at temperature extremes of between -40C to 120C.  

The thread on this type of nut can often be identified by the colour of the nylon insert, with blue signifying metric and white for imperial threads. This is not always the case though, so be sure to double check before purchasing the wrong type! 

Flange Nuts 

A flange nut is a combined hexagon full nut with an integrated washer. The flange provides an additional surface area to spread the load, reducing pressure in one spot. This greatly reduces the chances of damage. 

The underside of the flange has angled serrations which prevent the nut from turning in a loosening direction. 

Lock Nuts 

Lock nuts are also known as half nuts, jam nuts and thin nuts. 

Lock nuts are used to keep a full nut in position, and stop it from working loose as a result of vibration. They are commonly used on car wheels. 

Dome Nuts 

Dome nuts, also referred to as acorn nuts, are nuts that cover the exposed threads of a bolt or stud. They feature a dome styled head and are available in a variety of finishes including brass, nylon, BZP and stainless steel. 

Wing Nuts 

Wing nuts, as the name suggests, have two 'wings' protruding from the side of the nut which allow them to be tightened just by using finger pressure. 

Metal Self Locking Nuts 

There are many notable brands of self-locking nuts, such as Aerotight, Cleveloc, Philidas, Philidas Turret, Stover and Binx nuts. 

These nuts increase friction between the threads of the two mating faces, which causes a slight distortion of the threads. They are often used when vibration is likely to be an issue and are also called stiff nuts, jam nuts and bent beam nuts. 

Self-locking nuts can be re-used, but they will lose their locking ability after a few uses. 

Cage Nuts 

Cage nuts, also known as captive nuts, are square nuts held inside a spring steel cage. The cage has two wings which are compressed together to allow them to be installed in a hole. The wings are released, and the outward pressure of the spring holds the cage nut solidly in position. 

Cage nuts are favoured in the automotive industry. 

Castle Nuts 

Castle nuts, or axle nuts, are slotted hexagon nuts with turrets on the top, resembling a castle wall - hence the name. 

Castle nuts are used specifically with bolts that have holes in the end through which a locking pin can pass through to lock the nut into position and prevent rotation. This pin is usually either a split cotter pin, and R clip, spring pin or a safety wire. 

Slotted Nuts 

Slotted nuts are often referred to as axle nuts. They are similar to castle nuts in that they feature the 'turret' top. 

They work in the same way as castle nuts, however whilst the diameter of the castellated section of castle nuts is slightly smaller than that the main wrenching section of the nut, this diameter is exactly the same for slotted nuts. 

Durlok Nuts 

Durlok nuts are high-grade hexagon flange nuts. They feature a serrated mating surface that stops any loosening from jarring or vibration. 

Most commonly used in engineering applications, they have a property class of 12, which is one of the highest grades available. 

Square Roofing Nuts 

Square nuts are used most frequently with roofing bolts. Square roofing nuts are available in metric sizes only and in a zinc plated finish. 

Shear Nuts 

Shear nuts are permanent fasteners that cannot be removed mechanically once their hex head has sheared, making them ideal for anti-theft purposes. 

They are a hexagon on top of a cone shaped nut - and only the cone shaped part is threaded. 

When the nut is installed, the hex sections breaks off at a predetermined torque, or when the nut is tightened fully. 

Once the hex section has sheared away from the conical base it can be removed and discarded, leaving just the tamper resistant cone in permanent position. 

Tee Nuts 

Tee nuts are nuts with 3 or 4 prongs attached to the flange on the top of the nut. This is to help ensure the nut can be set into wood and give a flush finish. 

Wood is pre-drilled to the size of the main body of the tee nut, and then the nut is set into the hole. The nut can either be hammered to create a flush finish or have a bolt and stud inserted. 

Both options will then require a nut and washer on the opposing side to the timber, pulling the prongs of the tee nut into the timber to give the flush finish. 

Weld Nuts 

Weld nuts are nuts that are welded onto another object. To install, pressure is applied to the projecting pins of the weld nut and a strong electric current is passed across the points of contact. This raises the surface temperature enough to weld the nut in place. 

It is crucial to remember that these nuts should not be plated, as the plating can interfere with the welding process. 

Spring Nuts 

Spring nuts are also referred to as Zebedee nuts, and they are rectangular headed nuts held captive within the Unistrut channel support system. 

Unistrut is a popular metal framework used in various construction applications, consisting of metal channels secured by threaded rods. 

Spring nuts slide along the inside of these channels and are used to connect threaded rods are multiple different pre-drilled points along the channel. 

We stock three different types of spring nuts at BOLTS.co.uk, long spring (the most common), short spring, and no spring. 

Threaded Connector Nuts 

Stud and connector nuts are extended hexagon nuts which connect two lengths of studding or threaded bar. They are often used in situations and applications where longer nuts are required. 

The length of our studding connector nuts are always 3x the diameter. 

If the nut you need is not on this list, or you cannot find it in the size or finish you require, get in touch with our team who can source of fabricate this to your need.