DIY Ball Mill

First of all I must point out that the basics used in the construction of my ball mill were taken from Cardew's "Pioneer Pottery". Cardew states that if the design for drum rotation is correct there should be almost zero wear on the drum - I have found this to be the case after over 30 years of using the same 5-gallon plastic drum.

The classic industrial approach with massive porcelain jars (which by their very nature makes sealing the materials inside difficult) is really taking a sledgehammer to crack a nut, as is often the case with old (tried-and-tested" traditional designs - who in their right mind would use a cone wheel when you can have thyristor-controlled DC motors for full torque at 1rpm?

I set out to design my ball mill using basic materials, minimal woodworking skills, and minimal reliance on outside help. Essentially it is just a rotating box (cage) with a lid, inside which is snugly fitted a standard 5-gallon plastic drum. The drum should be about one third filled with flint pebbles between 1" and 1.5" diameter. This will hold 20lbs of dry material with 2 gallons of water. The drum is filled with dry material via a funnel, and the whole thing can be lifted in and out of the cage easily. When milling is finished simply unscrew the lid and pour through a 40s mesh sieve - the pebbles remain inside the drum.

Unless you can weld the bits you will need to get made are two 6"x6" plates with a shaft welded to the centre point of each and dead true. The shafts should be the same diameter as the pulley holes. I found that with a standard 5-gallon drum with a diameter of about 10" I would need two 2.5" and two 12" pulleys; this steps the motor speed down to around 60rpm for the drum which is about right.

The whole machine can be made from an 8'x4' sheet of (ideally) 1" ply - I used shuttering grade rather than best WBP - and several feet of 3"x2" softwood. The first part to make is the cage - which should take the 5-gallon drum as exactly as possible - too loose and it will thump about in use, too tight and it will be difficult to get the drum in and out. I use a recycled screw fitting to keep the lid closed, but any quick-release device would do. The two 6"x6" plate/shafts are bolted to each end ensuring that they are as true as possible ie in line.

The rest is so simple I feel the picture tells you everything you need to know - it's really just a case of making measurements to suit the parts you are working with and cutting appropriately. I would recommend the belts which are made up of multiple segments for coarse adjustment.

The most extreme use I have made of this machine is a 72-hour session with porcelain clay for David Winkley - apart from the background noise, no problems. I always mill all my glazes for about an hour, mainly to get a really thorough mix rather than reduce particle size substantially.

Updated 5th February 2009