The smaller ring (for @fiz) is 2mm wide and the large one (for me) 3mm. Using my widest saw blade (yes widest) I have cut a grove round the circumference of the rings. I started with the large ring and it's a bit rough, off centre and wobbly in places but the practice has paid off and I did a lot better on the small ring where it is going to need to be spot on.
Tomorrow I will start again and make them without all the dents.
