Backyard Ballistics (tm)

Ball Mill

I built a Ball Mill. Of the type commonly known in the hobby as a "Sponenburgh Mill". I bought the book "Ball Milling Theory and Practice for the Amateur Pyrotechnician" by Lloyd Sponenburgh from American Fireworks News. Or was it Harry at Skylighter. (both Excellent sources). I highly recommend the book. You can likely ferret out the minimal required information off rec.pyrotechnics, but it's useful and instructive to at least be exposed to, if not comprehend, the contents of the book.

Here's my ball mill:



The top electrical plate houses two switches - one for the motor and the other for a fan. I typically set the switches and just plug/unplug the extension cord remotely. Think Safety. The fan is handy in summer to keep comps & the mill cool. The cord end stows in the bottom cover.

This mill is capable of running two 1 gallon milling jars, each with 40 lbs of lead and ~ 1kg of composition. Perhaps only once have I run two jars, and I'd suggest that, unless you are really going into production, you only need one jar's capacity. Your mill will be lighter and less cumbersome! I also found that for me it's difficult to keep up with such a fast mill unless one is in serious production mode - either stocking up or granulating comp or cutting stars inbetween batches. I'm not that young (!) and find that I quickly have enough comp for future projects in mind and can backfill in a hurry if necessary.

 I can mill 1kg batches of pulverone in 3 hours that is comparable to 24-48 hours in a rock tumbler mill. 15 minutes or less to powder oxidizers, 5 to mix in dextrin (different jars!). So, if you can, build a Sponenburgh Mill, and consider building a single jar model (though I highly recommend the capacity of the 1 gallon jars - mixing 1kg batches in 3 hrs is sweet).

I've built 1 gallon jars out of 6" PVC and quart and half gallon jars out of 4" PVC. The smaller jars are useful for powdering  smallish amounts of  oxidizers. I had trouble finding Sch 40 6" PVC so settled for DWV PVC and it's been holding up fine.

 Cutting lifting bars on the radial arm saw. Watch your fingers!

Here's a gallon jar cylinder with the lifter bars being glued in place. I used PVC cement, but you haveto clamp it as it's a solvent weld and you need tight, intimate contact, for the bars to glue properly and not come off.



Here's that  gallon jar cylinder with the lifter bars in place.



I melted down wheel weights and cast these 3/4" slugs. Melting wheel weights is messy & smelly, but they're free. I got a whole bucket of them free for the asking from a tire shop. It took a whole bucket of wheel weights to melt down to the 100 lbs of lead you see in the next picture.

Casting alloys are expensive unless you can find them surplus. The best deal I've heard of, and my next target for when I need more media, is to pick up lead alloy bird shot at the local skeet/trap range. It's cheapest when bought in large bags (eg 25 lbs) and when they've paid shipping in bulk. I think it works out to less than $1.00 a pound - a price I'll pay to avoid the mess/smell of wheel weight cleaning. And the alloy will be known.


This is about 100 lbs of cast lead. It took a full bucket of wheel weights to cast down to this. Each 6" jar takes 40 lbs of lead.