Logan Oplinger on wed 17 dec 03
On Tue, 16 Dec 2003 17:43:07 -0500, wayneinkeywest
>Never having seen a ball mill, I was,er, um, stunned
>at the price various companies wanted.
>Thinking about how a ball mill does what it does, my
>father's spirit kicked me in the butt and said
>"you can do it cheaper", so I started thinking.
>I often have access to electric clothes dryers that
>have burned out elements, but still turn just fine.
>Even a used one that still works is only $25-50 here.
My little gem tumbler just couldn't handle anything larger than a 2 qt.
porcelain ball mill jar, so this past weekend I built a ball mill from
scrounged, surplus, recycled, and hardware store materials for under $30.
The power source now is my heavy duty 1/2 inch variable speed drill, which
has been doing nothing most of the time. When I attach a drive wheel to
the mill I will also be able to power it with my Shimpo wheel (it is
quieter :^D ). The mill is about 2-1/2 inches high, 2-1/2 feet long and 10
inches wide. I don't have the space for a recycled electric clothes dryer.
I cannot diagram it in perfect detail, but I can describe the materials and
how it is put together. The bearings (25 cents ea.) were made for roller
blades or razor scooters, and are attached to the ends of the rollers. The
rollers are 1/2 inch aluminum electrical conduit covered with 3/4 inch I.D.
clear pvc tubing. The rollers are 15 inches long. The rectangular frame
is made of 5/16 and 3/8 inch threaded rods. The "pillow blocks" which hold
the bearings are made of high strength sched. 80, 3/4 inch pvc water pipe
fittings, 3 elbows & 1 tee. The elbows & tee also form the frame corners
to which the threaded rods are attached, with holes drilled into the elbows
& tee at 90 deg. The connection between the ball mill drive roller and
drill is made with a 6 inch length of 9/32 inch aircraft cable with
a "coupling nut" epoxied to each end. This cable acts as a flexible
connector so that the drill does not have to be in perfect alignment with
the drive roller. A short piece of compressed air hose may also work.
To view the diagrams below, all text should be in a monospaced font such as
The pillow blocks: 3/4" sch. 80 pvc elbow & tee. Side view showing elbow.
| . | ___|
| o / << two 5/16" holes drilled opposite through each side, below "ear".
o_____o << two 3/8" holes drilled opposite through "throat" and "neck".
|___| << 1" section of 3/4" pvc pipe inserted before drilling holes.
Notes: I used the raised lines on the fittings as guides for marking and
centering the holes.
I inserted the 1" section of pipe to raise the assembly a little, and to
add strength where the 3/8" holes are drilled. NO adhesive, or pipe cement
The tee has one end branch cut off, and looks similar to the elbows from
the side. The holes are drilled in the same positions.
The rollers: Side view & partial cross section at wire spacers.
\_______________|_ << 3/4" I.D. clear pvc, 16" to 17" long.
/ wire spacer> ~~~|__<< 1/2" alum. cond., 15" long.
\ |__| << 5/16" coupling nut, 1-3/4" long, CENTERED IN COND.
/ |__|\\\\\\\\ << 5/16" threaded rod, 2 feet long.
\ wire spacer> ~~~|__|
/_________________| << JB WELD epoxy packed in space between nut & conduit.
\_______________| ^ Coupling nut extends out 1/2".
*/ \* * = wire positions around coupling nut
Notes: The easiest way to fit the clear pvc tubing over the conduit is to
cut it into 2" or 3" lengths, heat the conduit & tubing in boiling water,
and force the now flexible tubing onto the conduit from both ends toward
the middle. Extra length is needed because as the diameter expands, the
length decreases about 10%. Lubricate the conduit very lightly with WD-40,
and wear cotton gloves, it's HOT! Trim of any excess tubing.
Coupling nuts are made for connecting threaded rods. Here I have used 4 of
them, 1-3/4" long, epoxied into each end of both rollers for centering the
threaded rod in the conduit. For each coupling nut, inserted in the space
between the conduit and nut, three equally spaced wire sections 1/2" long,
made from 14 or 16 gauge wire hold the coupling nut centered, and should
fit snugly. The threaded rod passes through the conduit and holds the
coupling nuts in each end in alignment until the epoxy has set. The
threaded rod must be PERFECTLY STRAIGHT.
The inside of the conduit, and the coupling nut MUST have all grease and
oil removed so the epoxy will adhere. To prevent epoxy from passing down
into the conduit, the end of the coupling nut which fits into the conduit
is wrapped with a couple turns of heavy string, tied, and held in place
with super glue. The conduit is held vertically, and epoxy forced into the
space between the conduit and coupling nut using the sharp end of a bamboo
shish-ka-bob skewer. JB Weld Epoxy needed for each end is about 1" each of
resin and hardener. Let the epoxy cure 2 hours before doing the other end,
over night before attaching the bearings.
\____|_ | __ | |
/ |__ _| |__ | |
\ |__|I|_| |__\ | |
/ |__|I|_| |__|\\\\\\\\\\\\\\\\\\\\\\\\ |__|I|_| |__/ ^
/______|^ ^ ^|__|^ ^
\____| 1 2 3 4 5 6
1.) Coupling nut. 2.) 5/16" lock washer. 3.) 5/16" nut. 4.) Bearing.
5.) 5/16" self locking nut. 6). 5/16" Threaded rod.
Notes: On the drive roller, the 5/16" threaded rod must extend through the
tee, so an additional 5" is needed on one end. This is where the flexible
cable coupling attaches. Otherwise, the threaded rod extends 1" beyond the
end of the rollers.
If the bearing fits loosely over the threaded rod, then a shim may have to
be inserted between the bearing and threaded rod. This shim can be made
from a strip of aluminum can cut 1/4" wide and 15/16" long and wrapped
around the threaded rod. The bearing fits over the shim.
Bearing Inserted Into End of Pillow Block (elbow or tee), tee shown in
***** >>>>> |_______________________|
I|__| |__\ flexible coupling
I| |__| | attaches here.
I| |__| |\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\I|__| |__| ^^^^^^^
| | _________ __
***** >>>>>_________| | | |
^ |________________ | | |
***** = Cloth packing. \ | O | |
| | ^ | |
| | 5/16" | |
| | hole | |
| | | |
| _|_ _|_ |
| | | | | |
3/8" holes>> _ __ __ _ <<
|_| | | |_|
| | | |
1" pipe section >>| | | |
3/4" pvc | | | |
Notes: The cloth packing allows the bearing to fit snugly into the block
and move slightly to allow for slight mis-allignment. Here I used a three
inch length of outside seam cut from an old pair of blue jeans. A 1/2"
strip, about 10-12" long of any heavy cotton cloth will work.
Layout of Frame: Viewed From Above, Minus Rollers.
*****|_____|*************************************|_____|* << tee.
+ ****** = 3/8" threaded rod. +
+ ++++++ = 5/16" threaded rod. +
Notes: All rods are held in place with either 5/16" or 3/8" nuts, and
threadlock. No threadlock is used on the 5/16" nuts marked with "A".
These are adjustable.
The 3/8" rods hold the pillow blocks in place for each roller.
Layout Showing Rollers in Place:
+ + ^ Flexible
+ + coupling
+ + attachment
+ HHHHH = Drive roller. + point.
+ XXXXX = Idler roller. +
+ +++++ = 5/16" threaded rod. +
Because I am using threaded rod, I can adjust the spacing between the
rollers depending on the size of container I am using as a ball mill jar.
I hope this helps in some way.
Another Tropical Island