I used the same tumbler, most of them will at one point need a little bulletproofing. Like tightening screws and having attentional belts. Now that the two original belts that came with the tumbler have broken I use a large 0-ring or what the call preformed packing.
You can see my recipe and results at tumbling coins and a few other items at this link: http://forum.treasurenet.com/index.php/topic,60777.0.html
You can see my recipe and results at tumbling coins and a few other items at this link: http://forum.treasurenet.com/index.php/topic,60777.0.html