What is the function of a castle nut?

• A. To secure a load-bearing joint
• B. To prevent loosening by using pins
• C. To connect different materials
• D. To cover the end of a screw

Answer: (B)

A castle nut is specifically designed to secure a fastener in place, often in conjunction with a cotter pin or wire. This combination prevents the nut from loosening due to vibrations or movement, which is particularly important in high-stress environments like machinery and automotive applications. The notched design of a castle nut allows a pin or wire to be inserted through the hole in the bolt, effectively locking the nut in place.

This feature is crucial in maintaining the integrity and safety of mechanical assemblies where connection failures could result in severe consequences. While the other options relate to general functions of various fasteners, they do not capture the unique security feature of the castle nut that specifically prevents loosening.