635 replies to this topic

[mminson]

Hello Everyone:

This being my first post to this forum, I beg your patience. I have read every post in this thread and have ordered materials to build my first ball mill. I have not decided on the size of my jar or the size/composition of the media. I am leaning toward 1/2" brass rod, as I can acquire that locally (Salt Lake City) and don't need to pay shipping. And BTW, if anyone would like some brass rod, I am picking up 24 feet of it this week.

Is there any data that suggests spheres are more efficient than cylinders?

Thank you Burlhorse for your excellent use of mathematics in relation to the size and RPM of the jars. Did the AFN article offer and clue as to how the OPTIMAL speed is calculated? I am torn between 6" pipe for the jar and a 3-5 gallon plastic bucket. I certainly do not need the whole 5 gallons, but given the option why not use a larger container?

Thanks for your thoughts.

Since Mark is already being used, you can call me Mince.

[phildunford]

Just to confuse matters, I sometimes use spheres and cylinders!

I added a few cylinders to my normal spheres and found the mill worked quite a bit more quickly. I think this may be because the speed of the mill is not optimal and the spheres can sometimes 'slump' on the wall. The cylinders seem to mix things up and make them tumble better.

In theory I would think that cylinders would not be so good, as there would not be so much contact/grinding surface. However in the real world theories don't always count for much!!

[sasman]

The AFN IV was an excellent 6 page article on ball milling..i wish i had read that before i bought my ball mill
Optimum RPM is 65% of the Critical speed
Critical Speed= 265.45 divide By Square Root of (jar inner diameter" - milling media diameter") Sorry I dont know how to use mathmatical symbols on this pc ....
EG.. 265.54 divide bySquare root of (6" jar - 1" balls)= 2.236)= 118.712 RPM
So 65% of 119rpm =77 rpm optimum speed for 6"jar with 1" media..

My Beech Ball Mill Ran at 33 rpm I had some pulley changes which took the speed up to 90rpm which i was going to put up with but having spent so much money i decided to do another pulley change and have now got My 30 lbs of lead media spinning at 72rpm ..
My optimum speed for my 6" jar and .690" media is 75 rpm
I would definately go the Brass media route..
Also Dont forget if you have optimum rpm you need to charge your jar correctly 50% Media 25% charge(Volume Not weight)..
Bigger Diameter jars grind Faster than smaller Dia jars..Use lifters bars to make sure your media is not slipping..
I would Buy the book By Lloyd E Sponeburgh on Ball mill making for lots of tips Etc..

sasman

[mminson]

Excellent stuff, sasman. Thanks for the data. I may just go out and buy that book before I invest too much time and resources into this venture.

Mince

[BurlHorse]

Hello Everyone:

This being my first post to this forum, I beg your patience.  I have read every post in this thread and have ordered materials to build my first ball mill. I have not decided on the size of my jar or the size/composition of the media.  I am leaning toward 1/2" brass rod, as I can acquire that locally (Salt Lake City) and don't need to pay shipping.  And BTW, if anyone would like some brass rod, I am picking up 24 feet of it this week. 

Is there any data that suggests spheres are more efficient than cylinders?

Thank you Burlhorse for your excellent use of mathematics in relation to the size and RPM of the jars.  Did the AFN article offer and clue as to how the OPTIMAL speed is calculated?  I am torn between 6" pipe for the jar and a 3-5 gallon plastic bucket.  I certainly do not need the whole 5 gallons, but given the option why not use a larger container?

Thanks for your thoughts.

Since Mark is already being used, you can call me Mince.

Mince,

Glad the math helped, as to a 5 gallon bucket, use the math formulsa and you decide. The Afn Article did not give the determining factors for optimal vs. criticle, but ti's quite asy to figure out mathmatically, by using the weight of the media and the linear wall so to peak of the ID of the mill.

Brass rods, or Bronz should be avoided when milling Amon. Perc as the the presence of copper sensitizes the AP, just a reminder. As to rod vs round media, depends on how often you want to replace liners/jars. Just as thought would be to use a bench grinder to bevel the edges of any rod media.

Anyway, thnaks, Stay green,

Bear

[Prodigy]

Guys, I've got a bit of a problem with my mill. It's a Beach tumbler that can take 1.5kg.

However, I've loaded it up with 800g media and 100g BP but it's only a small portion of the barrel size unfortunately. I'm in the process of making some more media (I melt my own lead) but I'm going to be way, way over the weight limit if I fill the barrel up half full. Will this be a problem?

At the moment it sounds like all the stuff inside is doing is slipping around in the bottom of the barrel, am I right in thinking this is going to produce rubbish BP?

[Yugen-biki]

...am I right in thinking this is going to produce rubbish BP?

Yes, most likely. Try using another tumbler or some other media. You may also try using less balls and see it it works. It?s not optimum but there will be no grinding done if the balls don?t move.
If overloaded the mill is sure to stop working. More cooling will help it survive longer but the solution is a bigger motor.

I?m using a rock thumbler with steel balls. It?s not full but works fine! I never mill ingredients together and I wash it every time I have used it. I?m thinking of a new mill for sulfur?...

[Prodigy]

Well the tumbler doesn't seem to have any problems at the moment, it turns fine although it's not a continuous motion, it's more like it does bits at a time, a bit stuttery but not in a struggling kind of way.

The media I'm using is basically bits of cut up lead bar, about 0.5 inch diameter. so they're like squares basically but I've hammered the edges a bit.

Would lead balls be better?

[adamw]

Yes, because then the mill wouldnt 'stutter' as the media can roll over itself.

[Phoenix]

After it's been running for a while the lead cylinders/cubes or whatever they are will probably hammer themselves fairly round. Mine did.

[LuMpY]

I've been thinking about make my own ball mill for a while now. I read on the forum that someone had a used a windscreen wiper motor. I reckon this a good idea as im only wanting to make 100g batches, but i dont really know where to look for a 220v - 12v transformer with enough amps to move it. Has anyone got any ideas, i have looked online but havent found anything at a senseble price. (apart from a car battery)

[alany]

It will cost you way more than just getting a mains motor.

My small mill uses a 50 W electric fan motor, and is just fine for doing 100 g batches of meal or other experimental compositions. It is definately the smallest I'd recommend going though. The fan motor was rebuilt after the ceased in service (as a fan) and has worked flawlessly ever since. It is an capacitor start induction motor so while it has a low starting torque it is also sparkless and inherently safe for explosive atmospheres.

Good bearings are the most expensive part of a ball mill. The motor is almost always available surplus for next to nothing. The belt and pullies often come with the motor. I used booker bolt for my rollers, and covered them with some PVC pipe to grip the rubber on the jars better. I use bearings that are designed for roller blade service, but were purchased surplus for about $1 each, they nicely fit some saddles for mounting.

[Stuart]

I've been thinking about make my own ball mill for a while now. I read on the forum that someone had a used a windscreen wiper motor. I reckon this a good idea as im only wanting to make 100g batches, but i dont really know where to look for a 220v - 12v transformer with enough amps to move it. Has anyone got any ideas, i have looked online but havent found anything at a senseble price. (apart from a car battery)

I have made many ball mill's from wind screen wipers. I don't think that it is really worth bothering with one if you are going to have to get a transformer and would be far better off going to your local scrap yard and getting a car battery from there. They are good motors, can run hours and hours and take quite a load. When using my straight through design, I mill 500g batch's using it and it weighs about 2kg although I intent to add another kilo of media.

If you look at the ball mill page in the temporary directory on my picture's site, you can read about my staight through design.
Stuart

Edited by Stuart, 07 March 2004 - 04:58 PM.

[LuMpY]

I didn't want to use a car battery because i thought the charge wouldn't last very long, and i would take a long time to charge. Getting a car battery would be a lot easier though. :-)

[Stuart]

A normal sized car battery will give you about 4 hours milling, maybe a bit more. Big batteries will last a good 7-10 hours. Charging time depends on the charger but I just put my batteries on for charge over night.

Stuart