Ball mill media

[otto]

Yep. Lead ain't what it used to be.... I've got a pretty good pile of soft and foundry waiting for reuse. Precast ingots are a crap shoot. Might have zinc mixed in among other stuff. Unless you're tight with your supply you'll never know until you melt it down.

 

I don't do the kind of volume you do Caleb so sacrificing a mold here and there doesn't hurt so much. I'm currently considering casting lead cylpebs in a home brew mold. Not hard to make and easy to replicate.

[dynomike1]

Is there any reason you couldn't use Zinc?

[lloyd]

1) You'd lose the density advantage of using lead. (look up their relative densities)

2) Zinc is a pretty active fuel, and not desirable as an additive to most color comps. For BP... I don't know.

 

Lloyd

[dynomike1]

What i am finding is the specific gravity of Zinc is less than Lead, but more than Ceramic. What i was thinking that there might be a contamination problem with Zinc since it seemed like everyone was dodgen it.

[passgas]

This is what I am doing . I am smelting wheelweights and adding 1.5 to 2 percent zinc. While still molten in my pot I will stir in some Zep rootkiller . This is suppose to change it into a hard lead/copper compound. Go to CastBoolits and do a search for Zep rootkiller. This is all new to me so I will do a 10# test batch and cast. If it works I may do another test batch and try raising the zinc percentage 1 to 2 percent. If it fails I just do the old fashion way and buy some linotype/wheelweight mixture. I will cast plain wheelweights to compare against. I will be casting 60 cal balls. Still waiting on my mold to come in. By the end of the next week I should get something going.

[MrB]

Why would you add zinc, just to then add rootkiller, and try/hope the sulfur parts of it burns of the zinc? At least that is what i think they are trying to do. Also, they use it as a copper medium for plating a copper "jacket" on to the bullets. At which point you got a copper contamination problem, and shouldn't use the copper coated milling media for fireworks.

Lead is good since it doesn't affect the fireworks effects. Copper is bad, since it's used to color shit in the sky, among other things. At that rate, casting lead in to copper pipe, and cutting it up is a better choice, at least the copper is think enough to be structural. Brings a whole different issue with lead working it self lose, and so om, but...

 

Anyway... Don't intentionally ruin lead by adding zinc to it.

B!

Edited March 6, 2017 by MrB

[MB3]

I use Alumina ceramic cylinders 1 pack of 13/16 $16 and 1 pack of 1/2 $7 from pyrocreations.com I mix the 2 togeather and its enough to fill 2, 3lb mill jars more the half way. In 4 hours they make very fast bp I have tried alot of diffrent media types and these are by far the best I have found. the only down side is they make the ball mill run a little louder and rougher but its well worth it

[lloyd]

"I mix the 2 togeather..."

---

<sigh>

L

[MrB]

As far as i can understand, he's using the same supplier, and 2 different sizes. It should be "safe" if either media can be considered safe to start with. They have similar optimal RPM, even if not identical, due to having the same density.

What are your objections?

 

I have no idea, hence asking. I've read recommendations for using different size media as a means to speed up the milling, where people claim it's more efficient, but it's countered by the claim that the smaller media will wear faster. Never really tested either claim, but faster wear seams... logical. And if the wear accelerates, the same effect should actually make for faster milling as well, so it sort of makes sense, i guess.

B!

[a2l]

I've got a small question but there's no need to make a new thread.

I've got a 1.5L (0.4 gallons) drum which I'm looking to buy lead media for. The diameter of the jar is just shy of 6".

Now I'm a bit torn on what size balls to buy. I know Lloyd recommended at least 1/2", but up to 1" would work as well. Yet more balls means more grinding, and lead is the heaviest media so I guess the ideal size is more towards 1/2"?

What are your thoughts?

[OldMarine]

I use ½" hardened lead in my 6" mill jar as well as in my larger one and achieve excellent results. Dave Forster has used smaller stainless media with good results but it requires longer milling times.

[a2l]

Thanks. And between 1/2" or 11/16", which would be the better one?

Hmm maybe I'm getting too hung up on this minor issue.

[OldMarine]

The ½" hardened lead is the gold standard and though Lloyd could give a more informed answer,I think anything larger would reduce milling efficiency due to larger spaces between the balls.

That said, I was just reading of a fellow with a 24" mill who uses billiard balls for milling charcoal. I think the media size is related to jar size but not sure how.

[lloyd]

"...I think anything larger would reduce milling efficiency due to larger spaces between the balls."

-0-

This is a hard one to explain to some folks. With smaller media, the spaces are smaller, but there are more of them, and the total amount of open space in the mass of balls remains the same, regardless of their size. It is approximately 60% solid, 40% open space.

 

The smaller media mills more efficiently (when each ball is heavy-enough to give the desired impacts), not because of the smaller space, but because there are more contact-points in a mass of small balls than in a mass of large ones.

 

As an extreme example, take a 6" i.d. mill, and put TWO 3" lead balls in there. There will be but one contact point between the two.

 

LLoyd

Edited March 16, 2017 by lloyd

[a2l]

Then it's settled, thanks guys.

[MrB]

The smaller media mills more efficiently (when each ball is heavy-enough to give the desired impacts), not because of the smaller space, but because there are more contact-points in a mass of small balls than in a mass of large ones.

 

Smaller media is most effective, as long as it's heavy enough to break whatever you are milling. There is something of a relationship where larger media is more effective at larger particles of the same material and as the size is reduced, you gain efficiency with smaller media.

Pretty much, there is a optimum size for everything.

At least that is my understanding. Again, i have been wrong before.

I'm using 10mm lead balls cast from mainly wheel-weights, with some added tin scraps, and water quenched when cast. Not really compared the media to anything else, but it works.

B!

[lloyd]

"There is something of a relationship where larger media is more effective at larger particles of the same material and as the size is reduced..."

-------------

Not for a given "friability". Small media works as well on a given substance, almost regardless of the particle size, until you get into 'large chunks'. But usually, 'chunky stuff' like lump charcoal is broken down into manageable particles before being ball milled.

 

Sure... if the pieces are larger than the spaces between the balls, you create an efficiency deficit. But not much, if they're smaller.

 

Lloyd

Edited March 16, 2017 by lloyd

[Boophoenix]

I use ½" hardened lead in my 6" mill jar as well as in my larger one and achieve excellent results. Dave Forster has used smaller stainless media with good results but it requires longer milling times.

 

I'm not certain longer times are always required.

 

You are correct Dave does mill for a decent amount of time, but a lot of that is to keep his tests standardized as that is what he started at originally. He did do some time testing and saw better results with longer times, but I don't recall the media used.

 

At some point ya have to ask is the added mill time necessary for the end use since the gains are going up way slower than the length of time. For wicked rockets yes maybe. For lift not really. For a good break could be debatable.

 

My personal belief is to mill with as little time as is necessary to get the result you want. I'm sure Dave won't mind correct me if I'm recalling anything incorrectly. We've had more than a couple of lengthy conversations about milling and media.

[MrB]

Sure... if the pieces are larger than the spaces between the balls, you create an efficiency deficit. But not much, if they're smaller.

 

Never thought about it quite like that. But yeah, that may well be where the perceived milling efficiency comes from. But i don't think stuff doesn't need to be quite as large as you indicate. If you have a 5mm space between the balls, and 3mm material to be milled, then your going to remove a lot of impacts simply since there isn't room for more then 1 particle in every "hole". It would quickly become under-filled as well.

 

And 3mm stuff still isn't what i would consider "chunky" to start with. I wonder how much difference rod-milling does in comparison to ball milling.

 

At some point ya have to ask is the added mill time necessary for the end use since the gains are going up way slower than the length of time. For wicked rockets yes maybe. For lift not really. For a good break could be debatable.

 

There is always a point of diminishing returns. To some extent it comes down to what is "good enough" for the individual setting the standard.

B!

[PeteyPyro]

I used to cast my own bullets in .451(45 Colt), .356 (.38 spl. & .357 mag., and .429 (44 spl. & mag.). I found that I could take a piece of disposable pine and drill 5/8" holes about 5/8" deep, and ladle my hardball alloy mix into the holes, then split the wood, to get decent ball media. Not spherical, but close enough. I tried to use .356 balls, cast for my 36 caliber Naval BP revolver, but they were a tad too small.

[lloyd]

Petey,

 

I've made molds in many ways, but the simplest and quickest was to make tubular aluminum foil molds (around a dowel), GENTLY embed them in dry sand (gently, so as to prevent them from being collapsed), and cast long rods of lead, which I subsequently just cut to length with bolt cutters. The 'funnel' that forms upon cooling was simply cut off and re-melted for the next batch.

 

Yes, they had a 'nip' on each end, but that smoothed-out in just a few dozen minutes of milling with a little waste media like a bit of sanded sawdust. (I added a few tablespoons-full of sharp sand to the sawdust before milling, then with clean sawdust to clean-up their surfaces and prepare them for product milling).

 

Lloyd

Edited May 20, 2017 by lloyd

[saltflat]

I bought some from woodys rocks here in missouri. Reasonable price and they are hardened

[lloyd]

You'll be good with Caleb's media. He does a good job.

 

Lloyd

[PeteyPyro]

I got my newest .50/.58 caliber hard cast, high antimony (12%?) alloyed lead balls from hqhandcast, or maybe handcasthq, on Etsy. They are some of the roundest and hardest alloy ones I've seen, but somewhat pricey. I used to hand cast my handgun bullets, but got rid of all my Lee moulds years ago. I've noticed shrinkage in my old balls, and I'm only 60~ish <grin>. But seriously, it seems the charcoal really eats away at even the hardened lead over many, many runs.

[PeteyPyro]

On second thought, these are probably too pricey and too nice to use just for media. Lloyd's right about Caleb's ball mill media, and I defer to him, since he 'wrote the book' on this ...(literally!)