Perfect Circle Jig for the Wood Lathe

This is a metal working and wood working project
This is a jig that I had thought about for a long time and then I had a job to make a lot of round top posts for a musical instrument maker and so I got serious about making one. I saw that Carter sells one and it is quite expensive. I remember my toolmaking boss said that "you appreciate it more if you make it yourself "....so I did!

I used some of Carter's ideas in my design. The base arm with the bearing is made of aluminum. All the rest of the parts are steel and finished with gun bluing The big knurled knob on the back of the cutter arm is for fine adjustment of the carbide ring cutter from Arizona Carbide. It has an infinite  range of radii that it will cut.. I have  5 post positions in the swing arm so you can set that up first for the range you will need to swing.  One of the positions is for concave cutting but that seems to chatter too much.
The hardest part is setting up the center the jig to the center of the radius to be cut. Some times it does not matter and you can be within 1/32" and that is okay. This jig is built to cut on the center line of my Nova Galaxi lathe which is 8" off the bed. Other posts could be made to use on different size lathes. The cutter arm has 3 flats milled on it so I can adjust the attitude of the cutter for a better finish - like scraping with a bowl gouge on the last cut

This  jig comes apart in 4 main parts and I made a  box to store them all in one place. The box is made from1/2" Baltic Birch and all the corners are lock mitered.
Cheers, Jim