Purple Pilot
If you want to stay away from the machine shop for the trimming of the fins on magneto...
I got a small metal cut-off wheel (3" dia and the mandral to hold it) and mounted it in my drill press. Set the table to desired height and started to slowly rotate the magneto. Cut those fins off nice and easy. It will not get the the center where the prop spacer would fit, but a larger diameter wheel would. I now have the tool for future use and save the trip to the machine shop.