Introduction: Cheap and Simple Ball Mill
Last year for the Fourth of July, I wanted to make some black powder to celebrate American freedom with a bang. However, one step in the manufacture of black powder is running it in a ball mill to grind it into a fine powder. I was not in possession of a ball mill, and Independence Day was quickly approaching, so I decided to make my own.
Step 1: Parts and Tools
- 1 length of PVC pipe (I used 6" of 2" diameter pipe)
- 1 PVC flat end cap
- 1 PVC male screw adapter
- 1 PVC female screw cap
- PVC cement (I didn't use any, but I would next time)
- 1 threaded rod (I used 5/16"-18 threads)
- 3 nylon locking nuts (5/16"-18)
- 1 wing nut (5/16"-18)
- 1 coupling nut (5/16"-18)
- 1 hex bolt (5/16"-18, make sure the bolt is only threaded about halfway)
- Balls for the mill (ideally lead balls)
- 5/16" drill bit (or whatever the diameter of your threaded rod is)
- Wrench for the locking nuts
- Vise-Grips / locking pliers
- Small rag
Step 2: Cut the PVC and Threaded Rod
First, cut your PVC pipe to your desired length with the hacksaw. I cut mine to 6 inches.
Then cut the threaded rod with the hacksaw based on the length of your pipe. It will need to be about 3 inches longer than the pipe, leaving room for the adapter, screw cap, and wing nut on one end, and the cap, nut, and half of the coupling nut on the other end.
Step 3: Drill the Caps
Using a drill and drill bit the same diameter of the threaded rod, drill holes through the centers of the PVC caps.
Step 4: Thread the Nuts Onto the Rod
Wrap the small rag around the threaded rod, and clamp the locking pliers around it. This serves to hold the rod still while you work the locking nuts onto the rod with a wrench. The rag is simply to protect the threads from getting disfigured by the pliers. You'll probably have to play around with how thick the rag is and how tight the pliers are to keep the threaded rod from rotating inside.
Start one of the nylon locking nuts onto the end of the rod, and use the wrench to work it down the length of the rod. You'll want to go down just far enough so that you can fit the screw cap over it and have just enough room for the wing nut to tighten over the cap.
Start another nylon locking nut on the opposite end of the rod. This nut will need to go down a bit farther, so that the flat cap will fit over it, and so that there's enough rod left to thread a second locking nut and half of the coupling nut.
Step 5: Assemble the Shank End
The shank end of the mill will have the shank used to rotate the mill.
Note: I changed my design after the initial build and I neglected to retake the pictures. The images are slightly inaccurate and show the screw cap instead of the flat cap on the shank end of the mill, but just pretend it's the flat cap.
Feed the long end of the threaded rod through the hole in the flat cap.
Using the same technique as in the previous step, thread a second nylon locking nut over the cap and tighten it down to hold it in place. Then thread half of the coupling nut onto the remaining portion of the rod.
Step 6: Create the Shank
Now you'll need to make the shank that allows a drill or something with a chuck to hold the mill and rotate it.
First, install the hex bolt into the coupling nut with a wrench until it's very tight. All the threads should be inside the coupling nut, with just the bare rod of the bolt exposed.
Then clamp down the mill and use the hacksaw to cut off the hex head of the bolt, leaving behind the smooth rod of the bolt.
Congratulations, you made a shank! (But not the kind you kill people with in prison.)
Step 7: Assemble the Body
Note: If you decide to use PVC cement, now is the time to get that out.
Slide your PVC pipe into the cap on the shank end. If you choose to use cement, apply it here.
Then slide the male screw adapter onto the other end of the pipe. (This is your second chance to use the cement and smell those fumes.)
Step 8: Assemble the Mouth End
For lack of a better term, I'm calling this end the mouth. It's the end you open to put in and empty out your powder (or whatever you choose to mill).
Screw the female screw cap onto the male screw adapter until it butts up against the locking nut on the rod.
Then thread the wing nut onto the remaining length of rod and tighten it down to hold the screw cap in place.
Step 9: Use It!
Now you get to put your new ball mill to use. Try to find some lead balls, since they are heavy and won't spark. I was unable to get lead balls at the time and tried using plastic BBs, but those are much too light to do any work. I was able to have some success using glass beads though (marbles would work too).
First, remove the wing nut on the mouth end, then unscrew the cap. Load up the mill with some balls and fill it with your material to be milled.
Note: Don't fill up the mill all the way, or it won't have any room to do it's job! Use plenty of balls and leave plenty of room for tumblin'.
Screw the cap back on and reinstall the wing nut, fit it to your motor of choice, and let it grind!
Step 10: Improvements
- Use a wider and shorter pipe.
- Use PVC cement for a better seal and stronger hold.
- Find some actual lead balls to do the milling.
- Implement some sort of screen in the mouth to prevent the balls from falling out when emptying the mill.
- Create a mount so the mill can be stationed on a table while spinning.