Hi Neil,
Yes the side is 90 degrees to the face. One thing I forgot to mention is that we cut the stainless discs just slightly over the finished size. All the caps have the 1/2" skirt so we cut the discs to the required finished diameter + 1+ and give an additional 1/8" per side for finishing.
Example on the 4", we cut the disc slightly over 5 1/4" in diameter and once mounted we machine the diameter true to 5 1/4".
The tool we use is a bearing mounted wheel, 2" diameter x 5/8" thick. I have tried 2 different type of wheels. The first one we used had a large corner radius and a second one with a 1/32" corner radius.
The larger radius wheel leaves a smoother finish and the smaller radius wheel gives a tighter size. After we adjusted the mandrel by the additional .020" we achieved a 4.00" opening with the large radius wheel. When I used the small radius wheel we got a size of 3.98" opening. but both have this .020" taper over the 1/2" skirt length.
The cap on the left was done with the larger radius tool and the one on the right was with the small radius tool.
