A couple of my 4" or so angle grinders have 10mm spindles and one or two have 5/8-11 spindles. I wanted to use 5/8-11 threaded wheels on the smaller ones, so I made some adapters. Then I found you can buy them ready made (they use a different approach from mine). Take your pick.
My webpage on the subject:
http://www.spaco.org/MachineShop/AngleGrinderSpindleAdapter.htm
Hey Pete. Great tip on these adapter. It is not something I personally have had to worry about as all my grinders have had the 5/8-11 spindles, but good to know.
I did notice a typo on that page though, and only that page. Up at the top you have links to your main sections. The “Blacksmithing” link is missing its “i”. Links go: “Home”, “My Machine Shop”, “Hole Tapping Tips”, “Blacksmthing”, and “Contact Us”.
On any other page, the link is spelled correctly.