Castle Nut

Castle Nut

A castle nut is a specialized type of nut featuring notches (or castellations) cut into one end. These notches give the nut its distinctive “castle-like” appearance. Castle nuts are designed to be used in conjunction with a cotter pin for secure locking. The defining feature of a castle nut is the slots or notches cut into one end. These notches are aligned with a hole in the mating bolt or shaft. For a castle nut to function properly, the bolt or shaft it is used with must have a drilled hole for a cotter pin. Once the nut is tightened, the pin is inserted through the aligned notches and the hole, then bent to secure the nut in place.