BIG Surface grinder. Shop in Minneapolis did 3 of em for us. Hardox 400 plate. They hated it too. lol. 3 days on a vibratory stress reliever to get it to finally stop moving around. Had to whack .045" off the faces. I chose this stuff because its nice and tough. Very abrasion resistant. Great for a sub plate in a dynamic shop where fixtures are on/off daily.