Copper "nuggets" for milling cems or BP

[hanabi]

Anyone ever try copper for milling chems or BP?

Found these recently:

 

https://www.rotometals.com/copper-plating-balls-99-99-min-oxy-free-1-pound/

 

Been using my own cast linotype balls for a long time and they have worked just fine.

When I mill an oxidizer by itself the result is grey oxidizer. Thought, maybe, these would work.

 

Joe O

 

[SharkWhisperer]

Interesting. Never heard of anybody milling with copper alone, likely because of cost. Lead is softer than copper on the Moh's scale, but is more dense (something like 11 g/cm³ vs 9 g/cm³; approximate values). Although harder, a little copper will eventually erode from your balls, but likely not to the same extent as linotype media. Grey oxidizer doesn't really bother me too much. Should be essentially non-sparking. But consider costs (including shipping). Your 5 x 1" diameter huge Cu balls cost about $10, not including shipping (I see the website offers free shipping over $99, so free if you buy 11 pounds). You have a mill the size of Texas and are using 1" milling media? Or you're going to melt these down and recast them as more typical 0.5" (13 mm) balls for milling? Given that halving the volume of a sphere approximately reduces volume 8-fold, that means you'd get, with no casting loss, 40 typically-sized milling balls from each 5 copper balls in a pound, for $9.35/pound, plus shipping, plus fuel/time costs for casting. For a slightly harder but less dense milling media than lead.

 

I don't know much about casting metals, but I do know that lead melts at a waaaay lower temperature than Cu, so that might be consideration (memory spits out like 620F vs 2000F--close but definitely not exact).

 

I recall paying about $16 per 100 of .50 cal unhardened lead musket balls last year (couple of pounds), plus tax but no shipping from a sporting goods store nearby. Didn't do much comparison shopping but antimony-hardened media is also widely available. Woody's sells 10 lbs of assumedly hardened lead balls, 1/2", for $60 and shipping. A buck/lb more if you want half that. Available elsewhere, too. Before shipping and (recasting?), your 1/2" copper ball-equivalent would cost around $23.40 per hundred. Sounds kinda pricey. If recasting, that company also sells 99.9% copper wire tidbits for $7/pound--a little more reasonable (and maybe faster/easier to melt/cast)?

 

Now wait a second: you might need to inquire further into that advertisement because it says "approximately" 5 balls/bag that are "about" 1" in diameter and equal a pound. If specs were spot-on, 5 x 0.5" balls would equal exactly 384.4 grams, which is 84.7% of a pound (volume of sphere = 4/3 x pi x radius³; mass = volume x density). But metals are their biz, so I'm sure their pounds are true pounds...

 

Guess it boils down to how much your grey oxidizer bothers you and your conscience, whether you plan to recast yourself (1" media?!!?), and cost.

 

Curious what you decide.

Edited June 16, 2020 by SharkWhisperer

[SeaMonkey]

Those copper balls are very high purity since they're made

for use in certain electroplating operations. Therefore, they're

quite expensive.

 

Copper is one of those metals that "work hardens" as it is

used. The more it is stressed the harder it gets until it

reaches its maximum hardness level. Therefore it would

be a good choice for a chemical grinding ball mill.

 

If one could find, or even make themselves, a heavily copper

plated lead ball, that would be much cheaper and near ideal.

 

I may just try that because I have a good supply of lead balls.

 

Although it is very difficult to melt and cast copper on a small

do-it-yourself scale, if the Copper Wire Tidbits that Shark Whisperer

mentioned above are No. 10 or larger in size a several pound mass

of those might work quite well as a grinding media.

 

After taking a look at the specs, 1.6mm diameter pieces are quite

small though. Has anyone here ever tried milling with tiny pieces

of metal?

 

Back in the early 90s I ordered some Brass Balls from this vendor.

They've gone up in price since then, but for grinding BP and other

chemicals they're really durable and clean.

 

A package of 25 1/2" Brass Balls runs presently $38.84 which isn't

cheap but they will last a very long time. They offer a wide selection

of sizes to suit whatever purpose one has in mind.

Edited June 17, 2020 by SeaMonkey

[snapper]

nitrate and charcoal will eat the copper up, nitrates chemically and charcoal physically..you would have to wash and dry after every use or risk patina growth as well. Brass, certain stainless types or hardened lead are the ideal choices..your lead neds more antimony if the oxidiser is coming out grey.

Edited July 16, 2020 by snapper

[Mumbles]

My impression is that it was usually the sulfur that goes after copper so hard. Copper and silver are chemically related. Anyone who's been made to polish the good silverware might be aware of the effect sulfur has on silver.

 

In any case, copper is fine from a sparking stand point. Brass is usually chosen since it's a little harder and tends to be a little less reactive. That said, both with get dull with time due to oxides/sulfides. Brass bar stock and a horizontal cutoff bandsaw is usually the economical way to do it.

 

As far as milling with smaller media, I do have some experience. There are trade offs, and I suspect there is a minimum acceptable diameter/weight. Smaller media will obviously have more balls per unit weight and per appropriate mill jar loading. The benefit to this is substantially more collisions per rotation. Most of the grinding and pulverizing in a ball mill happens between the balls from media on media impact. This results in a faster milling time, or given the same duration, a potentially finer grind. Think of it like accomplishing a traditional 8hr mill run in 4hr. Those are just for illustrative purposes, and not any real or approximate values. On the downside, smaller balls have substantially less weight, so there is less force delivered from each impact. This results in a reduced crushing ability. I find this is most evident in it's ability to crush larger chunks. Using smaller media requires a finer grind of chemicals going in in my experience.

 

I was using 00 buckshot as a milling media for a long time, which is about 0.33" in diameter. It's a pretty economical source, and hardened. The black powder was excellent coming out and very fine. The trade off is I had to pre-grind all of my charcoal and nitrate going in. I was using prilled nitrate at the time, which was not ground effectively. If you cook your own charcoal and get lump out, it required pre-processing. I used a meat grinder with fairly good success. I passed it through a window screen, and it seemed okay. Using straight lump charcoal, it would grind some of the softest pieces, but generally leave larger rounded off chunks. Granted my charcoal source at the time was not optimal. Using soft lump from home cooking probably would work. I'd bet the thinner flakes from ERC would also be just fine.

[CrossOut]

Probably get more value selling the copper off and buying lead! Lol.