Castellated Nuts
Castellated nuts, also called castle nuts, have slots cut into the top so a cotter pin or safety wire can pass through a drilled bolt and lock the nut in place. They're used where a nut must not loosen, such as on control linkages and other moving joints that would otherwise loosen a nut. Monroe Aerospace stocks AN310 castle nuts for tension loads, AN320 shear castle nuts for shear-only loads, MS17825 and MS17826 self-locking castle nuts, and MS14144 and MS14145 castellated locknuts. Stainless versions, such as AN310C, are also available.
Castellated nuts are slotted to accept a cotter pin or safety wire. See how they're used in our nut guide. Pair them with drilled-shank AN bolts and the correct size cotter pins.
