I should probably speak up here as I mentioned a 52mm ring. I've measured some of my medium sized cutters and the vast majority are 41 - 46 mm. I use a few though (Wealden's tenon cutter, sash cutter and kitchen door set) that are 49mm, so I thought increasing the second ring by 2 mm would be useful. I'm OK with buying more blank discs to cut my own rings if everyone else prefers 50mm though and the 30mm disc is fine.Dibs-h":2z4my5q6 said:p.s. If folk think the 30mm & 50mm dia holes aren't quite right and feel that 2 other sizes would suit better - speak up. Can't really do different sizes for different folk - we'd have to settle on 2 sizes (probably).
Agree entirely with ijam's reasons for choosing steel plate and aluminium discs as well.