pics
Made a 1 " collar for my old Belsaw mower blade sharpener then used a variety of stones (and files and hacksaw blades etc.) hand-held against the sprocket as it spun at high rpm ... whee
Took about 2 hours of work, but finally got it down to fit 520 chain. for the final inside radius that i couldn't get a grinding stone into I fired up the angle grinder with a cut off wheel, hit the switch and lightly ran it into the sprocket in the opposing direction of rotate ... "don't try this at home"
Didn't blue out the sprocket at all, gave it a lot of breaks to cool down, hopefully didn't loose much of the hardening in the teeth.