Harrison M300 Change Gear Calculator

This tool can calculate possibly alternative gears that can be used to cut a particular thread on a Harrison M300. It is heavily based on the work of Al Harral; I just thought it would be nice to have a web-based alternative for those (like me) who don't use Windows very much.

I haven't done a lot of sanity checking on this calculator yet, so if you notice any mistakes or problems, please don't hesitate to get in touch.

I am a hobbyist metalworker and woodworker. I work as an electronic design engineer and spend most of my working days in front of a computer so I enjoy having the opportunity to use my hands and make things in my spare time. I particularly enjoy making tools as I can then use them on other projects. This website showcases some of the things I've made.

This website is free and ad-free, but costs me money to run. If you'd like to support this site, please consider making a small donation or sending me a message to let me know what you liked or found useful.

Please do get in touch if you notice any issues on the site or can think of anything that would be a helpful addition or improvement.