Thread: Case tumbler

Have been thinking of making my own case tumbler. Instead of making up platform, rollers, bearings etc, I thought I might just make an adapter to stick a wee plastic tub on my brake lathe that I use for work(one of my flatmates empty whey containers is looking good, with a couple of agitators in there..). It's obviously quite capable of spinning a drum full of water and brass as it usually has brake discs on it (up to 380mm OD, 30mm thick sometimes).. My dilemma is that it's a fixed speed jobbie which I've timed at roughly 50rpm, and I've been told that tumbling at speeds over 30rpm potentially damages the brass.

Is this true? Or just go for it and be careful how long I tumble for..