I needed to grind up some cat little to test if it would be suitable as a source of bentonite clay, I needed a ball mill but I didn't want to spend a lot of time making a decent ball mill if the cat litter wouldn't suit my needs.
Step 1: What you will need
a plastic tub ideally with a screw top
a cordless drill
1 nut or wing nut
and some lead balls, you can make these using the following instructable