yet another ball mill discussion

[Bender222]

I am about to construct a ball mill and I was thinking about something I read in Sponenburgh's book. He said the larger diameter jar the better because the media ultimately had a longer distance to travel. Wouldnt a short jar with a large diameter be more efficient than the ones that he contructed?

[Arthur]

From my experience a drum with a large diameter will mill faster than a small diameter drum. Milling largely happens where the layers of lead balls are rotating against one another so a deeper bed of lead balls will give a better faster milling.

[tentacles]

Bender, that's correct, a larger drum is more efficient. I think the standard "sponenjar" design is a compromise between a reasonable size and the cost of larger PVC fittings. Also, anything bigger than 6" PVC or fittings for such is not readily available at a hardware store. IE specialty shop needed.

[Swede]

Agree, and I like 6" as a good medium diameter that will still fit an average ball mill. Adequate media for an 8" jar is going to be a lot.

 

Companies like US Plastics will sell 6" or 8" fittings, but their minimum pipe order is 10 feet, and the prices for all of these is not cheap. I am always on the lookout for scrap PVC at construction sites. It is amazing what you can pick up off the ground on occasion. Most of the wide-bore stuff is used for drain, waste, vent applications, which use a different sized fitting that the pressure-rated stuff, so watch out for that.

 

A Specialty plumbing store, not Home Depot or Lowe's type stores, should probably have both pipe and fittings, and I'll bet they have short sections available as cutoffs.

 

For a really deluxe jar, I think one of my winter projects is going to be a 6" jar, doubled on both ends with cut-off caps, and 316 SS studs plus an o-ring on the lid, held down with nuts. About three of those should set one up nicely, with smaller jars dedicated to chlorates and such.

[dagabu]

I have a bunch of friends in the construction field, if you want to get some PVC and fittings let me know and I will see what I can get and ship it to you to glue together.

[Bender222]

Just a random thought, what about an empty Whey protein "jug"? I think you have misunderstood my words before when i was talking about diameter. I was commenting on using a larger diameter jar with a smaller length so that the volume would still be near the same of the normal jars. they would use the same amount of media and hold the same charge but the diameter of the jar would be greater and according to sponenburgh as far as diameter goes, bigger is better. Since i havent biult the mill yet I could possibly accomadate the increase. Or would the increase not make a huge difference?

[NightHawkInLight]

Just a random thought, what about an empty Whey protein "jug"? I think you have misunderstood my words before when i was talking about diameter. I was commenting on using a larger diameter jar with a smaller length so that the volume would still be near the same of the normal jars. they would use the same amount of media and hold the same charge but the diameter of the jar would be greater and according to sponenburgh as far as diameter goes, bigger is better. Since i havent biult the mill yet I could possibly accomadate the increase. Or would the increase not make a huge difference?

I understand what you are saying. A mill 8" in diameter, but perhaps only 4" in length. As opposed to a 6" jar being 6" in length. I have seen some commercial mills of the same design. I believe it could potentially work better, though perhaps not noticeably. I'm not entirely sure.

[QED4803]

As an utter novice, I'm trying to soak up as much as I can. It appears that a ball mill is pretty much a must, but I have a couple of questions and concerns, to wit:

 

What about electrostatic discharge?

It seems most of the containers used with ball mills, as well as many of the drive components, are traditionally made of plastics. Having spent most of my life in the electronics industry, this just screams "ESD" at me. Are there any known issues or recommended precautions in this regard? Even Napolean had ESD processes in place for his powder magazines!

 

To mill or not to mill?

In different places and at different times I see the following advice:

NEVER ball mill mixtures other than BP.

NEVER mill metals.

This certainly seems like good advice, but then I read about milling MGAL, etc. in posts by seemingly rational and cautious practitioners. I can only assume that there are rare exceptions for the well trained and capable that must be carefully researched and cautiosly practiced. Am I roughly on track?

 

Thanks for a great forum!

 

QED

[TrueBluePyro]

You are able to mill kno3, sulfur, charcaol and dextrin if you want.

As you said never mill metals, exspeiacly when in the presents of oxidisers.

 

Lets say you want to mill a glitter and it has these chems:

 

kno3

charocal

sufur

dextrin

Aluminium

 

If you wanted to mill that for a little bit, dont add the Al to the mix and mill it without the Al. After milling, add the Al.

 

Miling MgAl is an exception, as it will turn into a very fine powder fast and is easy to crush. If you are to mill MgAl, make sure you use a different mill jar and different media. You can use SS media for milling MgAl.

 

For milling BP chems you must use NON-sparking media.

[NightHawkInLight]

Here is the rule: *Any* individual pyrotechnic chemical may be milled, but only certain mixtures of chemicals may be milled together, such as black powder. MgAl may be milled because it is merely a fuel (more accurately a mixture of two fuels), it must have an oxidizer to burn explosively. In general that is accepted, though there are many precautions that must be taken when milling MgAl because it tends to rapidly oxidize when the jar is opened if milled continuously for to long at once. That would cause a brilliant and dangerous fire, but not a concussive explosion.

 

Be aware that milling metals or any individual chemicals not compatible to be milled with one another means having separate mill jars as well as separate media to prevent cross contamination.

 

Though your thoughts on ESD seem very valid, I have never known an accident to happen when opening a mill jar because of it. It could be because the only mill acceptable compositions such as black powder are rather tame, or for one reason or another static does not build well under the circumstances. Yet another possibility is that discharges do occur, but they are always relieved on the outside of the jar before opening.

 

Most pyrotechnics take the very wise precaution of only wearing cotton clothing rather than synthetics, both for static reasons as well as fire protection. Many will also ground their work table. That is as far as any usually go. I do not suffer from many problems regarding discharges due to high humidity during the seasons I usually build.

[QED4803]

Thanks to all for the clarification. I broke down and bought the rock tumbler from Harbor Freight--with sales and coupons they practically paid me to carry it home. I'll replace it with something more substantial when I have more experience and some appropriate parts.

 

Meanwhile, another batch of questions: Can I alloy the ton of lead in my scrap heap with Sb to harden. and if so in what ratio? Also is there an easy source for the Sb?

 

Thanks,

Smitty

[Mumbles]

You can try to alloy it, but it's easier said than done. The lead has to be heated a few hundred degrees above the melting point of lead to get it to alloy. 5% usually seems to be pretty good. They sell Sb on ebay I think. You'll have a much easier time purchasing high antimony lead for reloading and alloying it down. 1 5lb bar of 25% antimony will harden enough soft lead for a 1 gallon jar. I buy linotype personally.