Almost free DIY ball mill/rock tumbler/rotary case tumbler

How to jerry rig a ball mill/rotary case tumbler for almost no money. Some metal working or wood working skills required!

Post build note: The rotary can (paint gallon) had raised edges on the both ends which was digging into the rollers so I had to wrap several loops of duct tape near top and bottom end of the can. The rolling force is now transferred through the duct tape which protects the powered roller rubber coating. And yes, this baby can do some serious milling!