What two factors determine the sizing of cotter pins?

The sizing of cotter pins is primarily determined by their length and diameter. These two factors are critical as they ensure that the cotter pin fits securely within the application it is intended for, whether it be for securing nuts, bolts, or other fasteners.

Length is important because it needs to be long enough to fit through the hole of the fastener and still allow for effective bending or securing of the pin's ends after insertion. If the pin is too short, it won't hold securely, while if it's too long, it could protrude excessively and create a safety hazard.

Diameter is also crucial, as it must match the hole size in the fastener to maintain a secure fit without being loose or overly tight. A proper diameter ensures that the cotter pin can be inserted easily but still provides enough friction to hold in place once it is installed.

In contrast, factors like thickness and strength, weight and length, or diameter and color do not directly influence how cotter pins are sized for specific applications. Thus, the focus remains on the length and diameter for proper fitting and functionality.