Answer :
Final answer:
The hardware item used with screws and bolts in the absence of a self-locking or castellated nut is the Cotter pin. This fastener is vital in preventing components from loosening, especially in machinery subject to vibration, by being bent around the nut or bolt once inserted. So, the correct option is A) Cotter pin.
Explanation:
The hardware item used with screws and bolts whenever the self-locking or castellated nut is not used is a Cotter pin. A Cotter pin (also known as a split pin) is a metal fastener with two tines that are bent during installation, similar to a staple or rivet. It is commonly used to prevent fastening components from becoming loose or falling off, especially in machinery where vibration is common. Cotter pins are inserted into holes of bolts or screw shafts that extend beyond the nuts. Once inserted, the two tines of the pin are bent outward, holding the nut securely in place and preventing it from unscrewing or loosening.
This method is widely used in various engineering and automotive applications, particularly in securing wheels, gear mechanisms, and other critical components. The term split pin is often used interchangeably with cotter pin, especially in the UK and Commonwealth countries, though the principles and function remain the same.
