There are a couple of 28 gauge chamber reamers with rim cutter and pilot floating around the PGCA forum. The reason is that early 28 gauge Parkers had smaller than normal rim recesses that needed to be enlarged. I did my first 28 gauge Parker on a Bridgeport vertical mill, right angle setup. It was a nightmare that I don't want to repeat. A PGCA member responded to me and offered to lend me his reamer. I don't remember his name. The Clymer reamer I borrowed made the rim cut a five minute job.