A castellated nut, sometimes referred to as a castle nut, is a

nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Co ...

with slots (notches) cut into one end. The name comes from the nut’s resemblance to the

crenellated A battlement in defensive architecture, such as that of city walls or castles, comprises a parapet (i.e., a defensive low wall between chest-height and head-height), in which gaps or indentations, which are often rectangular, occur at interva ...

parapet of a

medieval castle A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars debate the scope of the word ''castle'', but usually consider it to be the private fortified r ...

. Castellated nuts are sometimes referred to incorrectly as castigated nuts. While castellated nuts are often referred to as slotted nuts, from a technical perspective, slotted nuts differ slightly from castellated nuts. Castellated nuts are formed with a round section at the top where the slots are located. Slotted nuts do not have this rounded modification. The flat sides of slotted nuts extend fully from the top to the bottom of the nut. Both castellated and slotted nuts are designed to use a pin (usually a

Split Pin A split pin, also known in the United States of America as a cotter pin or cotter key, is a metal fastener with two tines that are bent during installation, similar to a staple or rivet. Typically made of thick wire with a half-circular cross s ...

) that fits through the slots and through a hole in the screw to which the nut is attached. This pin prevents the nut from turning and loosening. Compared with slotted nuts, castellated nuts allow the cotter pin to be confined closer to the margins of the nut itself, providing added secureness. The bolt has one or two holes drilled through its threaded end. The nut is

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

d properly and then, if the slot is not aligned with the hole in the fastener, the nut is rotated forward to the nearest slot. The nut is then secured with a split pin/cotter pin,

R-clip __NOTOC__ An R-clip, also known as an R-pin, R-key, hairpin cotter pin, hairpin cotter,. bridge pin, hitch pin clip or spring cotter pin, is a fastener made of a durable but flexible material, commonly hardened metal wire, resembling the shape of ...

safety wire Safety wire or locking-wire is a type of '' positive locking device'' that prevents fasteners from falling out due to vibration and other forces. The presence of safety wiring may also serve to indicate that the fasteners have been properly tigh ...

. It is a positive locking device. Castellated nuts are used in low-torque applications, such as holding a wheel bearing in place.

References

Nuts (hardware) {{Mech-engineering-stub