I have an Oregon Blade Maker, Bader Style grinder and just bought a 4" rubber coated contact wheel with a 1.18" (30mm) inside bearing bore. I'm in a bit of conundrum as to how to attach it to my tooling arm, which has 1/2" and 5/8" threaded holes. I thought a 30mm diameter shoulder bolt that stepped down to 1/2" or 5/8" would be the answer, but can't find anything close to that online. Any suggestions? Thanks.