It's pretty hard to find anyone who can bore a drum because the axle is so
small at the small end and most brake drum lathes have a big enough shaft
that it won't go through. A good machine shop with a big lathe could
do it for you but it would probably be pretty expensive unless they did it
regularly and had the appropriate fixtures.
If it is just scored around and not too rough, I'd seriously consider using
it as is.
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George Downs Bartlesville, Heart of the USA!