This is my affordable rock tumbler designed to tumble 3D printed parts, printed with ColorFabbs metal filled filaments (BronzeFill, BrassFill, CopperFill). It is also possible to add a 'golden' shine to regular PLA when the parts are tumbled with brass screws. It should be possible to build this tumbler for less than € 40.- which makes it much more affordable than 'professional' tumblers that can do nothing better than this one ;-)With the 110mm drum it turns with approx. 22rpm - feel free to adjust the speed using different gear wheels (see note below).You can go with a drum of your choice (i.e. old tins, etc.) but I found that PVC pipe couplings that are sold in hardware stores are perfect and cheap. This tumbler is designed to run with either diameter of coupling like 110mm, 125mm or 160mm (latter not tested yet). The 110mm drum is large enough for most of my parts and should be the starting point for your first try. For those who like a rubberized drum it is a good idea to print the inset for the drum with flexible filament.Full instructions here: http://www.instructables.com/id/Affordable-Rock-Tumbler/