18 replies to this topic

[smiley]

Hey all.

I'm building my own ball mill however i'm not sure where i can get the lead non-sparking balls from in Australia. If anyone could point me in the right direction, it would be greatly appreciated.

Cheers

[RegimentalPyro]

Try looking for bullet moulds on ebay. You can make all the media you need then.

Edited by RegimentalPyro, 10 January 2006 - 07:55 AM.

[Frozentech]

Hey all.

I'm building my own ball mill however i'm not sure where i can get the lead non-sparking balls from in Australia. If anyone could point me in the right direction, it would be greatly appreciated.

Cheers

Do the automobile repair shops there use lead weights for balancing tires ? If so, ask them for the discards when the change tires, and cast your own. A google search should turn up a lot of instructions on how to cast lead. They do not have to be balls, short cylinders work very well also.

[alany]

I've used fishing weights from "$2 stores", they work fine but are expensive compared to buying scrap lead and casting your own. The local metal bloke has scrap lead flashing for < $1 kg, him and I get on real well now, I buy all his Magnesium scrap too.

[minalth]

Lead is easy to cast, you can even make your own moulds by drilling holes into a piece of wood, being sure to dampen the wood but not make it wet. This makes short cylinders which work fine.

[koobee]

Perhaps I am alone here but I personally discourage the use of lead media. I use ceramic cillinders as the lead has presented me with problems. Often the media would break and small particles of lead would scatter in my comps. Maybe thats just me but I strongly recomend ceramics. I have been told that gem stores would carry something like this. I got mine from my pyro teacher.

[Frozentech]

Perhaps I am alone here but I personally discourage the use of lead media. I use ceramic cillinders as the lead has presented me with problems. Often the media would break and small particles of lead would scatter in my comps. Maybe thats just me but I strongly recomend ceramics. I have been told that gem stores would carry something like this. I got mine from my pyro teacher.

Hmmm... well, Mr. S.B. ( a seller of fine Paulownia charcoal and other pyro goodies ) would beg to differ after blowing up his mill. He had a mill explosion using ceramic ball media. I'll ask him if I can post his story here. Many pro's recommend ceramics *only* for milling pure chemicals, no fuel/oxidizer mixes. They *can* spark.

I generally use brass for milling BP. I bought brass as 3/4" hex bar stock and cut it into 1" long pieces. Works great.

[Frozentech]

OK, I found the earliest post about the ceramic media / BP milling accident I referred to: I've spoken to the 'anonymous' person in email and asked about (some of you probably have purchased materials from him) and to this day he won't use ceramic media for black powder.

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

From: "Lloyd E. Sponenburgh" <llo...@Bridge-City.com>
Subject: Explosions from milling BP??
Date: 1997/06/03
Message-ID: <339427CD.5CA3@Bridge-City.com>#1/1
X-Deja-AN: 245812544
Organization: Bridge City Enterprises, Inc.
Newsgroups: rec.pyrotechnics


The person who had the ball-milling accident wishes anonymity, but
really wants to share with you what happened, so you can benefit from
the safety lesson. The event was described to me thus:

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


The ball mill was home-made with a wooden drum. The sides and lifter
bars made from maple and the top and bottom made from veneer core birch
plywood. It was believed to be airtight, and had been used several
times to mill black powder. The media were ceramic balls about 3/4" in
diameter, purchased from a ceramics supplier. The mill had quite an
aggressive lift and drop action ( Ed note: This is contrary to modern
industrial milling practice -- L.S.) This was before publication of
Lloyd's book, and information on ball mills was scanty and
contradictory.

At the time of the explosion, the mill had been running for about an
hour.

It was 100 feet away from a dwelling. The load was several pounds of
black powder made from agricultural ingredients. The explosion shook the
house, and fragments of the mill were found up to 70 feet away. I do
not know what caused the explosion, but I no longer use ceramic media
for milling BP.

----------- end recounting -----


And there's an implied statement here that since the person switched to
lead milling media there have been no more explosions.


Lead does not mill as _fine_ as ceramic, but it tends to mill a bit
faster until it reaches terminal particle size. That's because the lead
balls are so much more dense that they whack into one-another with
tremendous force, even over the fairly large contact area afforded by
soft media.

Ceramic media grind much more slowly than lead because of two issues:
One, they are less dense, so fall with less kinesis than lead. Two,
they are very hard. Ceramic media make contact only at TINY spots
because the balls are so hard -- the balls do not deform upon impact.
This means less material is between the points of contact.

It also means that the contact pressures of ceramic can actually be
much higher than lead. At very high impact pressures, heat can be
generated by friction and crystal fracture faster than it can be
dissapated by the media or material. The high 'lift and drop' action of
the mill being discussed would have worsened that effect.

Very likely, this was the mechanism which caused the explosion.

Some people have speculated a piezo-electric effect may have caused it,
but there is no evidence to support that. Most commercial ceramic media
are sintered aluminum oxide and porcelain. That material is not well
known for its piezoelectric properties. Certain titanium-bearing
ceramics (like Barium Titanate) do manifest very energetic piezoelectric
effects, but I surmise from the story (perhaps incorrectly) that these
milling balls were not 'special' ceramics in any fashion.

LLoyd

[smiley]

Fair enough, my only concern is the purity of the lead i obtain. Is there much chance of sparking if there are other contaminents in the lead.

[Frozentech]

Fair enough, my only concern is the purity of the lead i obtain. Is there much chance of sparking if there are other contaminents in the lead.

Well, if you cast your own ball or cylinder media from the lead you will not have any contaminant problem, certainly nothing that would spark anyway. A certain amount of antimony is desired in media, as it hardens the lead so it will last longer and not 'smudge' off and discolor any pure chems you mill. Wheel balance weights contain antimony, as does linotype metal.

If you cast your own, when you melt the lead, you will add flux, ( beeswax usually ) to it. All the contaminants including any stray iron or steel bits, will float to the top of the lead, along with oxides and dirt. Skim that off, and what is left will be clean, shiny lead alloy perfect for casting ball mill media.

It's identical to casting bullets, which I used to do on almost a weekly basis.

If muzzle-loading rifles are an allowed hobby where you are, you can buy melting pots, lead alloy, ladles, and molds at a shop which specializes in that hobby.

[koobee]

I withdraw my prior recomendation. I had no idea that ceramics could spark. I will do some looking into this. Although it seems that it could have been a number of other things that perhaps caused the ignition, I will most likely be changing my media. Thanks!

[smiley]

Thanks frozentech, now i've got a bit more of an idea on what to do, well ill try get some wheel balances from the mechanics and take it from there.

[Pepsi]

Hey all.

I'm building my own ball mill however i'm not sure where i can get the lead non-sparking balls from in Australia. If anyone could point me in the right direction, it would be greatly appreciated.

Cheers

Why not use 1/2" or 3/4" round lead sinkers, available at Kmart... ..cheap :-)

p

[maximusg]

Yeah I can vouch for the sinker idea I went to the local crazy clarks ($2 shop) and bought out all the sinkers. They were $1 a packet... you got about a dozen of the little tiny ones in a packet, half a dozen of the 12mm ones and 4 of the larger elongated ones. I spent about 20 bux and got heaps.

[smiley]

cool, if they're that cheap, for sure!