Sorry for the lame duck post. Let me explain my procedure. This is for us poor folks who can't afford +$35 dollars for a little chip of metal.
I took a glue stick and made an impression of the slot the key sets in and then found a drill bit that closely fit the radius of the key impression on the glue stick and then cut steps into the ditll bit. See photos. And then cut it off and cut the offset. And there it is.
I made sure to cut it double wide to give myself a little room to work with and bring it into spec.
Use a long fine file to hune it down and needle files to fine tune it. When you get it close enough to use the needle files go one or two passes and mic it. Keep monitoring all surfaces that are in contact with the file. It can quickly get away from you.
Be patient and use good light and magnifying glasses if you got them.
I'm making this one for my friend and isn't quite done but you get the idea. I hope these help to simplify it for you.
