What's the deal on lead media?

[Frozentech]

Pipipi, it's nothing more than 3/4" round brass stock, cut into 3/4" lengths. For larger jobs, I cut some 1" diameter rod into 1" lengths. I used a metal-cutting bandsaw, which made short work of it, but with some effort, a hacksaw will do. The cost of brass is insane, but at least it'll last essentially forever.

 

Comparing my attempts so far with lead vs. brass, I like the brass MUCH better. The lead balls seem to gather the chemicals to themselves and hang on tenaciously, whereas the brass media separates very cleanly, and washes much easier than the lead. I am going to go all-brass for future milling projects.

I also use brass media for BP, charcoal, and a few other chems. Remember NOT to use brass for milling Ammonium perchlorate though. My media is 3/4" hexagonal bar stock from www.onlinemetals.com, cut to 3/4" lengths. I haven't even used my lead media, which now sits in a bucket outside my garage someplace, for 2 years now. I know what you mean about the initial cost, but like you said, it's a once in a lifetime investment, and cost far less than my average Skylighter order !

[KinneticEnergy]

I need to get some lead media myself, I think I'll get the stuff from pyrocreations...Unless you want someone to take/buy that media off your hands FT

[InRainbows]

Kinnetic, your much better off with eBay. I got 200 .562 cal balls for 21$ with shipping. And 200 of those would be around double that at pyrocreations.com.

 

Or a lot of people get it from gun shops, if you live near one.

[mormanman]

I'm not sure but I don't think anyone has. Anyway, I heard on this forum that the most efficient shape for media is a cylinder and cut at a 45 degree angle (flat top of course).

[KinneticEnergy]

Kinnetic, your much better off with eBay. I got 200 .562 cal balls for 21$ with shipping. And 200 of those would be around double that at pyrocreations.com.

 

Or a lot of people get it from gun shops, if you live near one.

That sounds like a decent price... Do you know of they are antimony-hardened(Assuming they are lead of course)?

[Swede]

I will NEVER AGAIN use lead media after today - here's why.

 

I was using a small jar + 400 round lead balls to make BP. These balls were brand new, and I made exactly 750 grams of BP with them. As I was washing out batch 2, I noticed how pitted and worn the balls were, and decided to weigh them. Each ball lost an average of 0.3 grams; they were worn from 11.5 to 11.2 grams after only TWO batches of BP.

 

More math - 400 balls, X 0.3 grams =

 

120 grams of lead in my 750 grams of bp!!

[edited: the math here is NOT correct! The correct number is 12 grams. I figured this out after FrankRizzo replied, and decided to leave this post intact rather than fudge it.]

 

 

That didn't seem right. I double-checked it, triple checked, and yes the balls lost 120 grams of weight. That is nuts. Before I go completely ape-$hit, can someone corroborate this? Weigh 10 used balls with a good balance or scale, and then weigh new ones OF THE SAME BRAND.

 

I don't know where the lead went. I'm guessing 90% of it is in my BP, and the rest lost as waste, highly toxic waste at that. If you've got hardened balls, wonderful. Maybe you'll only get 30 grams - OVER AN OUNCE OF LEAD - per kilo of BP.

 

This hobby carries enough risk of toxicity and/or maiming without adding lead poisoning to it. That is an insane amount of lead. It burns in the BP, making Lead oxides that drift in that pleasant smoke cloud everyone is sniffing.

[FrankRizzo]

Yes, you will always lose a bit of lead to the mill charge. One way to reduce this contamination is to use a harder alloy of lead (one with antimony or tin) instead of the dead-soft musket balls. Another is to cast the balls yourself and quench them in cold water right after they begin hardening..this will add a few brinell hardness points.

 

Also, check the RPM of your mill jar to make sure you're milling in the optimal range and not slower. Slower RPM's encourage excessive media-on-media friction.

[Swede]

I am so embarassed - mea culpa - I made a basic math error. The lead loss was 0.3 grams per 10 balls, NOT 0.3 grams/ball, so the 400 balls' loss was 12 grams, not 120. I was tempted to edit my post, but it had been up for a while.

 

I thought that seemed a bit much! Tin or antimony in the mix would certainly help, but it's too late for me as I bought the balls pre-cast. FR, thanks for the pointers.

 

I tend to be a real safety nanny and the thought of people inhaling significant amounts of lead was disturbing. It is up to everyone else to decide if 10 to 20 grams of lead per kilo of BP, if using soft lead, is a danger or not.

[marks265]

Swede

 

 

I feel better now. Also if this was your first run for the media I would check again after a second run and see what your losses are.

[justanotherpyro]

I've been told that it is a good idea to dry run new media a few times. This might be a reason why. A few dry mill runs probably packs the lead a bit or loosens up areas of the ball that weren't cast the best.

[moof]

Would these be good enough to use as milling media : http://cgi.ebay.com/50-1-2-solid-brass-bea...4QQcmdZViewItem

 

If it is, does anyone know a cheaper source?

Sorry if this in the wrong section.

[Swede]

Moof, those would rock for a ball mill, but look at the cost - $28 per 50, or over 5o cents per ball!! 500 of them would barely do for a jar that's 4" in diameter by maybe 6" long. It is amazing how many balls you need for even a small jar.

 

The cheapest brass you are going to find is going to be round or hex bar stock that you'll need to cut, and even then it'll be expensive.

 

I have some ceramic media coming that I will reserve for pure chemicals only, no mixtures, and the media will stay with the chemical - at least that is my plan for now, until I see how porous the ceramic bars actually are. But for BP, it'll be brass for me. I like it's performance and I love how easily it separates and cleans up.

 

I have hopes for the ceramic media. It's odd that we should have such trouble finding good media at a good price. Even if it's lighter, the ceramic media should work fine - I'll just have to run the mill longer. Electricity is cheaper than expensive brass stock.

 

If we knew (perhaps someone does know) of a stainless alloy that is 100% guaranteed sparkless, that would be great. But in industry, for spark-free tools used in dangerous environments, they alloy of choice is beryllium copper, and again, you're looking at major $$.

[JCrewPyros]

Swede how much was the brass stock that you had gotten? I figure since you work in a shop as such I can get the same prices here. I just haven't had the time to ask my roommate how much he can get it for.

[TheSidewinder]

FYI, I paid $36 for a 18 foot piece about 3 years ago. I paid a couple bucks extra for the supplier to cut it into 6-foot lengths so it would fit in the car.

I know the price has gone up, and I think a fair bit, since then.

[FrankRizzo]

You'll probably pay ~$4-$5/ft for .5" brass rod stock these days. Cutting will be the PITA. My suggestion would be to rig-up a miter box from a piece of steel channel and use a sawzall to cut it. Using a hacksaw would be brutal.

[tentacles]

Frank: speaking of brass stock, did that 1.25" rod arrive yet?

 

There's no reason you can't use stainless; as long as it's a 300 series alloy, 18/8 or 18/10. The 400 series is more prone to sparking, but even with that series, you would have a more than difficult time getting a spark in a milling situation. Even a grinding wheel surface moving at 64mph (3600 RPM / 6") throws only sparse sparks.

 

It's expensive, though - even at scrap prices you'd be looking at $1/lb - buying it as scrap from the source - at a scrapyard probably twice that, if they have it, and if they will sell it to you.

[FrankRizzo]

Not yet as far I know. I left the house this morning before the mail had come, and haven't been back since. It may be waiting for me when I get off work in a few though. Thanks again!

[tentacles]

Frank: I like the avatar, is that by chance one of those MgAl flash reports?

 

I picked up a new 10/14T bi-metal bandsaw blade today, and cut up like 7 feet of that 1/2" SS rod. Still have another ~5ft piece to do, and some 3/4" rods that need to be diced up more. Since I don't have a grinder, and don't approve of what grinding does to SS, I'm going to clean up the ends of each piece in my lathe. I actually think it's faster than grinding, too - it only takes about 15 seconds per piece.... times a few hundred pieces. I'll just watch a movie while I do it.

[FrankRizzo]

Very nice! It might be a bit of work, but I bet your media will last forever.

 

The avatar pic is a frame of video from that day we went out and launched those shells and leftover PGI rockets last year. It's one of the Windex-moderated™ rockets with 5g 70:30 + 10% MgAl that CATO'd. I was watching them again last night as I ran a backup and happened to pause just as it blew-up. Kinda reminds me of a nuke.

 

Edit: Still no sign of the brass today. You sent it regular post, right?

[tentacles]

Expedited, the lady said 9 days max. I have a tracking number at home somewhere. I'll have to dig for it after the cleaning the other day.

[Swede]

Tentacles, what stainless alloy are you going to use? And are you planning on using it for mixtures like BP, or are you going to reserve it for pure chemicals?

 

A quick google "stainless tumbling media" turned up these guys. Interesting stuff.

[tentacles]

Unsure of the specific alloys - probably all 304, though some may be the free machining 304 as it cut so much nicer on my lathe. I rounded the edges on every single piece cut so far... I have some pics..

 

ALL of my stainless is austenitic type - non magnetic, ie 18/10 or 304, 316. "3 series". The coffee can with more in it is the 1/2" the other is mixed sizes, 5/8-7/8". I will mix it all up in order to load my mill jar enough - hopefully if I combine all the stainless I have, I can load an 8" jar.

 

http://www.apcforum.net/files/DCP_2526.JPG

 

http://www.apcforum.net/files/DCP_2525.JPG

 

http://www.apcforum.net/files/DCP_2524.JPG

[Swede]

After looking at some of the commercially-made stainless tumbling media, I really want some. There must be a source for it in less than pallet-sized quantities. Perhaps a way can be found to obtain what they'd call a "professional sample!"

 

I especially like the ones that look like little flying saucers! I'd bet they'd perform spectacularly.

[tentacles]

Even if you can find it in less than pallet quantities, it probably sells for $3-5/lb. Stainless is an expensive material to begin with, and when you factor in the cost of machining this tough stuff... $_$

 

I've spent probably a good 6-8 hours cutting and rounding my media.. and I'll be lucky if there's enough to fill 1/3 of one of the 8" jars I've just about completed.

 

edit: Someone did ask earlier (Swede I think) what alloy stainless I was using - the 1/2" I am sure of at least, since I know where it came from. It is 316 stainless, sold as scrap by a company that supplies hospital grade metals, they have a "shelf life" on their products and everything that is over 18 months old gets sold as scrap, wastefully.

[Swede]

edit: Someone did ask earlier (Swede I think) what alloy stainless I was using - the 1/2" I am sure of at least, since I know where it came from. It is 316 stainless, sold as scrap by a company that supplies hospital grade metals, they have a "shelf life" on their products and everything that is over 18 months old gets sold as scrap, wastefully.

316 is great stuff and as unreactive as SS can get. But how the heck does stainless steel "expire?" That cracks me up!