Ballmill

[seawolf]

I need some advice on building a ballmill. I have a piece of 1/2" wall steel pipe that I can cut a foot from, Several widths of flat bar, end cap from an old compressor tank, variable speed motor 3/4 HP.
I intent to cut a 3" hole in the center of the end cap and weld on a threaded half collar to load and unload the steel tank onto a screen over a bucket. Build a roller table to turn the tank.
My questions are.
Should I use just one flat bar to raise the balls to the top? Or use an odd number 3 - 5?
How tall of a flat bar for the riser?
What size balls would be best? 1/2 3/4 1 11/4 mixture of each?
How many balls to use?
Should I have a stand off under the flat bar/s to allow the material being milled to slide as the mill rotates?
I can adjust the RPM so the balls fall into the material. I know that 30 -35 RPM will be the starting point for adjustment.
I hope someone who has built or bought a ballmill can help me out.
Mark

 

[Barren Realms 007]

There are several ball mill threads by "mic" and "Rusty" that you can search for and get some of your answers.

 

[rusty]

What diameter is your pipe, the 1 1/4" balls would be my choice. I'm using six 3" balls, more would be better and faster.

My home made mill turns 60 rpm, with one lift bar, a stand off under the lift bar wouldn't hurt.

I don't care for your idea of a hole in the center for unloading your mill, this means that your homogenizing your material during the off loading, from my experience I have found that the gold and heavier metals tend to settle out onto the bottom of the mill - high grade if you skim the top powders off carefully.

Please note HOME MADE does not make me an authority.

Regards
G

 

[seawolf]

The pipe I have is twelve inch. You have given me another idea. A friend has a dry panning unit that he uses in the summer months while placer hunting. Might this be a way to seperate the heavier PMs from the ceramics?
Mark

 

[Harold_V]

Should I use just one flat bar to raise the balls to the top? Or use an odd number 3 - 5?

Do it right and you don't have need for any internal bars, nor do I recommend they be used. If they are a requirement, it's because the ball mill is running the wrong speed. That's already a bad idea.

Harold

 

[rusty]

Should I use just one flat bar to raise the balls to the top? Or use an odd number 3 - 5?

Do it right and you don't have need for any internal bars, nor do I recommend they be used. If they are a requirement, it's because the ball mill is running the wrong speed. That's already a bad idea.

Harold

We seem to be undecided on the lift bar, I use one and it works fine for me, after all it's only a hobby.

Re: Home built Ball Mill from junk yard parts

Postby 4metals » October 6th, 2010, 8:06 am
My experience with ball milling was heavily slanted towards jewelry sweeps and crucibles and slags. Because of this I found a lifter bar was needed. I too used a charge equal to half the volume of the mill. I also had 5 different size mills. One of the mills had no lifter bars, it performed admirably on the jewelry sweeps but they are rather easy to crush in any crusher. When it came to slags and broken up crucibles, the mill without lifter bars was woefully inadequate. It seems the lifting and dropping of the balls helped to crush the larger pieces of hard material.

Originally we used all of our mills for any crushing task based on the size of the lot, but over time we realized the mill without lifter bars would not crush hard materials as quickly as the others so it was not used for slags and crucibles.

If I were designing a mill myself, I would include a lifter bar so it would be more versatile and quicker. Larger pieces were ground up in a mill without lifters as Harold said, but it was a long process. Keep in mind that the lifter bars cause more impact on the mill itself so the walls have to be thick enough to take it. The commercially manufactured mills I used (generally Paul O Abbe) were built to take it.

 

[goldsilverpro]

With the right speed, no lifter is required. Ideally, the correct centrifugal force makes the balls cling to the side and then drop once they approach the top. That way, you get a desirable pounding action rather than a grinding action. The size of the balls is important also. Most of the balls I've seen used on the forum are too small for most materials

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=3107&p=27909&hilit=ball+mill#p27909

 

[Anonymous]

While I do agree with Harold and Chris,that you do not need a lifter bar to drive the media up to the optimum drop point,I will have to disagree about it not being needed in a mill.
At the optimum speed the ballmill will in fact create a "centrifugal" effect on the media inside......the problem is,it also creates a centrifugal effect on the media.Therefore a very large portion of the material will not be in the "sweet spot" on the bottom as the media drops.An elevated lifter bar like I created all but eliminates this problem by allowing the media to be lifter at a slower speed,yet allows the material to slide between the media and stay on the bottom of the chamber.There is one other element needing to be addressed though.The drop point still may not be in the "sweet spot".There is an easy way to fix this though,simply raise or lower your lifter bar.When you test your mill,use vice-grips to hold the lifter bar on the upright supports,then run the mill while watching where the media lands.If it lands behind the material,lower the bar......in front of the material,raise it.When you have decided on the best height,tack it in place,remove the grips and finish welding.
I have fine tuned my mill to the point where I can grind 15-20lbs of cpus into nothing but dust overnight.If I had better media,I could cut that time down,or run more at once.
Here are the specs:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=8247#p76888