Slotted & Castle Nuts

Trojan Special Fasteners Ltd can manufacture all manner of slotted and castle nuts.

Castle nuts are typically hex nuts with usually 6 slots (60 degrees apart) in a reduced diameter round section above the wrenching part. When a castle nut (or any radially slotted nut) is applied to a threaded section, it is tightened so that it's slot is aligned with a predrilled hole in the bolt or threaded rod, into which a cotter pin, split pin, a lock wire or a spring pin is typically inserted to stop the nut from rotating.

These kind of nuts are unsuitable when a specific preload is required because the torque can't be fine-tuned - a result of rotating a nut to align it with a hole for pin insertion. Additionally, such nuts require an additional component and alignment time.

Typically split pins, cotter pins, R clips or safety wires can be used to stop the castle nut from loosening.

Castellated, slotted and castle nuts are commonly used on axles and are even called axle nuts in some applications. Sometimes they are used on trailers too. They are also used as hub nuts which hold the driveshaft within the wheel hub assembly.

In addition to standard preferred sizes, we also manufacture non preferred and non standard or special thread and nut forms and sizes. If you have a drawing, or a sample Trojan Special Fasteners Ltd will make what you want.

We can manufacture from single quantities all the way up to the thousands.

Predominantly these forms exist:

1. Radially slotted nuts

Slotted Nut

Castle Nut

2. External groove slotted nuts
These are also known as roller bearing nuts and are fastened with a hook spanner. They have one washer bearing face and depending upon the size, they can have between 2 to 8 equally spaced external slots.
Hook spanners are defined by DIN 1801A standard which give specific internal diameter, hook size and wrenching length, in order to apply the correct amount of torque for nut application and removal.

3. Axially slotted nuts

Axially slotted nuts (like those pictured above) are typically used as all metal prevailing torque type nuts, where the axial slots are used to create a section that can deform the thread by pressing the top parts down. This increases friction between mating threads and thus increases the application and subsequent removal torque of such nuts. Being all-metal these nuts are not subject to chemical and temperature limitations of their nylon insert counterparts.

There is frictional interference between the threads of mating components which creates resistance that is called prevailing torque. This type of nut can be reused, but only a limited number of times.

These are very useful in applications where there is a degree of vibration that would loosen regular nuts that have not had their threads locked by another mechanism. However, this axially slotted type of nut is typically only one-way.

Please note that Trojan Special Fasteners Ltd does not manufacture trademarked fasteners unless by order of the trademark holder.

Trojan Special Fasteners can axially slot and deform nuts to provide a prevailing torque feature on your nuts - as no open standard for these exists we would ask that you provide your dimensions or a drawing and we can manufacture to that. Additionally, we can torque test most of your nuts for you, just provide us with the female threaded part and we'll take care of the rest!

Frequently Asked Questions

What are slotted nuts used for?
Castle and slotted nuts are primarily locking nuts, which means that once they are fixed they are designed to lock into position. This is achieved by using a cotter, split or taper pin or wire which winds around the castle or slotted portion of the nut and through a pre-drilled hole in either a bolt or portion of threaded rod. In this way, the pin stops the nut from moving free by virtue of it impeding the nut's movement due to the slots it passes through.

What is the difference between a castle nut and a slotted nut?
The primary difference is that castle nuts have a turned-down (turret) portion on the slotted end. With a castle nut, a pin can be wound round and pinned against the turret portion in order for the pin not to stick out too much. Otherwise castle and slotted nuts are effectively the same thing.

Why do castle and slotted nuts have slots?"
Castle nuts and slotted nuts have slots so that they can accommodate a cotter, split or taper pin or wire, which prevents the nut from loosening.

We can manufacture to the following specifications:

Standard Description
ASME/ANSI B18.2.2 Heavy hex slotted nuts, table 11
ASME/ANSI B18.2.2 Hex slotted nuts
ASME/ANSI B18.2.2 Hex slotted nuts, table 5
ASME/ANSI B18.2.2 Hex slotted nuts, table 7
ASME/ANSI B18.2.2 Hex thick slotted nuts
BS 1083 Hexagon castle nuts
BS 1083 Hexagon slotted nuts
BS 1768 Hexagon thick slotted nuts - unified threads
BS 1768 Thick hexagon slotted nuts
BS 1768 Thin hexagon slotted nuts
BS 1769 Hexagon black slotted nuts - unified threads
BS 1769 Hexagon heavy black slotted nuts - unified threads
BS 3692 Hexagon castle nuts
BS 3692 Hexagon slotted nuts
BS 7764 Hexagon castle nuts
BS 7764 Hexagon slotted nuts
DIN 1804 Slotted round nuts
DIN 546 Slotted round nuts
DIN 70852 Slotted groove nuts nuts
DIN 935-1 Hexagon castle nuts
DIN 935-1 Hexagon slotted nuts
DIN 935-3 Hexagon slotted nuts
Standard Description
DIN 937 Hexagon thin castle nuts
DIN 937 Hexagon thin slotted nuts
DIN 979 Hexagon thin castle nuts
DIN 979 Hexagon thin slotted nuts
DIN 981 Slotted round lock nuts
ISO 13754 Hexagon slotted nuts
ISO 288-1 Hexagon castle nuts
ISO 288-1 Hexagon slotted nuts
ISO 7035 Hexagon castle nuts
ISO 7035 Hexagon slotted nuts
ISO 7038 Thin hexagon castle nuts
ISO 7038 Thin hexagon slotted nuts
NF E22-111 Heavy series slotted round lock nuts
NF E25-411 All metal prevailing torque hexagon nuts with slots - HFR
NF E27-413 Slotted round cylindrical nuts
NF E27-414 Hexagon castle nuts
UNI 5593 Hexagon castle nuts
UNI 5593 Hexagon slotted nuts
UNI 5594 Low Hexagon castle nuts
UNI 5594 Low Hexagon slotted nuts
UNI 5595 Hexagon castle nuts
UNI 5595 Hexagon slotted nuts