Close. I don't have the time at the moment to do the math but... A 1" wide blade needs a 1/4 thick spine. Go from there. 4 to 1 is the magic number. So you're in the ballpark. I read a lot of folks use 4 to 6-inch wheels for grinding. But I have never made one so its just what I remember reading. A Razor Maker will be along shortly.