oh...hey...that's no big deal

what t-mar said, but i'd alternatively suggest stuffing a paper towel down the seat tube, use the rat tail/half round file, and then an extendable magnet (or whatever magnet on the end of your driver/chisel) to get filings out. just a thought

edit: alternatively, again, you might instead use an automotive brake cylinder honing tool. they insert into any drill and can be rented at most auto parts stores. might oil that paper towel, too, so filings will cling to it. and, again....magnet