Bought a cheap drum sanding kit from ebay some months ago. Four drums and lots of sanding tubes to use on my bench drill. Worked OK but some of the tubes just would not fit well on the little drums - some too big others too small. So I've been taping up the too small barrels to stop the tubes slipping. Hey - it only cost a few bucks. Today I need the smallest drum radius and I can't get any of the smallest tubes to slip over. In frustration I thought I'd take the drum off so I see this little nut at the bottom of the drum on the shaft. I turn it counter-clockwise (universal loosen, right?) and what the hell - it doesn't loosen - it tightens up and the drum gets fatter! And the nut is reverse threaded so when I turn it clockwise, it loosens and the drum gets smaller.
Nobody ever told me you could make the drums bigger and smaller with this nut thereby making it easier to get the tubes off and on! DOH!