Many types of watch band links are held in place with cotter pins. If you need new cotter pins for your watch band repair you can use this guide to learn how to measure a cotter pin to order replacements.
Take your old cotter pin and lay if flat on your work surface so you can easily access it. Start by measuring the length of the cotter pin. Take your digital gauge and open the jaws wider than the pin itself. Then pick the cotter pin up and position it between the jaws of your gauge. Carefully close them until they grip the cotter pin securely.
Repeat this measurement a second time to double check your results. This will give you the length of your cotter pin
Turn the cotter pin over on its side so that you can measure the diameter of the pin. Open the jaws wider than the pin again and position the cotter pin in between the jaws so that you are measuring the middle thickness of the pin. Close the jaws until they grip the cotter pin snugly.
This will give you the diameter of the pin. Repeat this measurement to verify your results.
Finally, with your measurements in hand, you can order new cotter pins for your watch band.