This method came to me in a rare flash of inspiration triggered by the happy coincidence of having materials to hand. I needed to polish 1" bores, 3" long in bronze, following a lapping operation. In casting around for ideas I found an old roll of nylon pile draught excluder strip, 6mm wide and 6mm deep, the self adhesive backing of which was long-dead, but that didn't matter as it turned out. I also had some broom handle available, from which I soon turned a mandrel around 3/16" smaller than my bores, 5" long. Still in the lathe, I drilled two transverse holes, one near the end, the other close to the chuck. By doubling the end of the nylon backing strip I persuaded it into the first hole, pulled some through, and trimmed off, then wound the strip tightly onto the mandrel in touching turns, and finished by tucking through the second hole. The resulting brush looked the business, as they say, so it was lightly dosed with a paste made from green buffing compound and light oil. A casting was carefully threaded onto the brush as it was a tight fit, but a trial run at low revs built confidence and in a short time I'd polished all three bores . Result !! For the benefit of anyone having a similar need I've found a source on eBay, to which I have no connection whatsoever :-

The Culley Family Shop, info@thehairyworm.co.uk, tel 0560 3449596 Five metres of 6.7mm wide, 6mm deep will cost you just £5.79, broom handle you can source for yourself, but be prepare to explain why the housebroom is suddenly shorter.