272 replies to this topic

[fishy1]

Why add risk? What if someone uses the steel ones to mill a composition?? Brass is not as expensive as the damage caused if something went wrong.

Well if someone is stupid enough to use steel media to mill a comp, it's their own fault. If you're milling up something like charcoal which is going to be used in a comp, I can't see a problem with it. He never said he intented to mill comps with it.

[karlfoxman]

I didnt say that either, I said if it was used for it. And what if someone does not know that steel will spark?! They will think, cool they are heavy and will be great for milling my bp. Dont forget some people on here have never ball milled anything. I regard using and steel in a milling jar is asking for trouble, contamination can occur . Some of that steel will go into the charcoal when its milled then if they happen to use that charcoal to ram a rocket or something then you have higher chance of an accident. Take the advice all of you.

[shadowpyro]

I already asked the guy at the metal works shop and somehow they dont have brass at all, only bronze-and that woulda cost me and extra ?10 which i didnt have!
i will be using separate componets when milling with the steel and not BP, it is only a tempory media until i can get hold of some brass or lead shot (the local gunsmiths didnt have that either!-unbeliebvably huhn?!).

[starseeker]

Hi guys,
a fix for the problem of the lead cast in copper pipe working loose is easily fixed by fitting copper end caps to your media,easily soldered on with blowlamp,not sure what size pipe your using but endcaps avallable in 15,22,28 mm from your plumbers merchants,

hope this helps,

[karlfoxman]

Get a 1/2" lead ball mold and make your own, thats what we did. Use roofing lead and melt it down in small crucible. Using heavy gloves and correct ppe gear pour the molten lead into the mold. You have to pour at constant fastish rate or you will get crap lead balls. To clean up the edges you can stick the lead media into the mill and just let them round themselves off. We made a good 1-2kg in 2 hours this way. But the best thing to use is brass as its non sparking heavy and very hard wearing.

[Andrew]

Steel rods makes a good job on Al foil, makes flitter and powder very quick.

However, NEVER even consider using steel to mill bp. (Or any comp for that matter, except maybe thermit!).

[shadowpyro]

lol i wasnt planning on it!
Though how long do you mill your aluminium powder for? and how often do you open the mill up to let oxygen in order to prevent "pyrophoricity" (if thats even a word heh heh...*ahem*)

[Andrew]

Here is a little advice on such a problem.

For the thread click on this link.

We have a 15 Litre mill which we keep in a hole in the ground. The primary reason for putting it there in the first place was because a 15 Litre mill is very loud. It actually hurt your ears if you were next to it. Just by having it in a hole, the noise envelope was shaped into a better but still unacceptable form. We put a 1 ton sack with about 200kg of earth in it on top of the hole, smothering the gap. Now you can not actually hear it unless you stand a couple feet away.

On a pyrophoric point, you can?t really avoid it as such, unless you stop milling well before it is down to a useful size. You can take steps to turn a pyrophoric material into one that is not though. You can add a coating to the milling jar contents part way through the batch. If you don?t do this and you suspect that the contents are pyrophoric, you should at least take the following steps.

Take the jar and shake it while upright.

Wait about half an hour.

Shake upright again, but considerably less vigorously this time.

Leave to settle for at least a few hours, over night is probably a good idea.

Open the jar very very slightly. Leave for an hour or so.

Repeat until the lid is off. You?re not out of the woods yet!

Leave for at least 24 hours as it is, without disturbing.

Put the lid back on and roll the jar a few times, until free flowing.

Leave to settle.

Open again, with caution!

You should be ok-ish by now.

If at any point the jar feels warmer than ambient, stop what you are doing, tighten the lid and place in a container filled with water, and then place all of this well out of the way, maybe in a hole if you have one!

There are tell tail signs that you can look out for. Like if the jar is warm, or the walls have collapsed inwards. The warmth is from the material reacting with the oxygen in the milling jar. If the jar is airtight, this will cause a lower pressure inside the jar, if your jar is not airtight the oxygen concentration will become slightly depleted but will replenish itself. For this reason, if your jar is not airtight, you will not really have to worry about pyrophoric material as much. If your jar is airtight, you will have a negative pressure on the inside, which makes the opening it in a controlled manor difficult.

On our 15L jars we are going to add an air tap, to allow us to raise the oxygen concentration at a controlled rate. Remember if it is pyrophoric, any oxygen will have already been consumed, assuming the jar is airtight, and the pressure inside will only be about 790mBar.

Edited by Andrew, 10 August 2006 - 04:55 PM.

[shadowpyro]

You mentioned that the pyrophric materials can be coated in a substance while in the jar, what can i use for it? stearic acid? or maybe something a little easier to get hold of!?

[Plays with Fire]

This seems like the most appropriate thread for my question I've been pondering...

What would be the ultimate milling media if you had infinite money to spend on it?

The first thing that came to mind was an extremely dense (maybe more than lead) core with a thin diamond layer...just a thought!

I'd like to know what ya'll think because I've been arguing with my friends (well, I would be if I had any ...) about this...

[shadowpyro]

Now im no expert on milling media, but my dad is and he deals with nanosize particles of stuff like aluminium etc (wow nanoscale aluminium powder!)
Anyway id probably say something like that as well, a really heavy core with an extremely hard surface-heh heh depleted uranium core with a tungsten carbide surface or something like that.

[Andrew]

The first thing that came to mind was an extremely dense (maybe more than lead) core with a thin diamond layer

Money no object, posible!!! but unless you are a millionaire I'd look else where.

depleted uranium core with a tungsten carbide surface or something like that.

Tungsten Carbide will wear away in time and you cannot have a thick layer as it is pretty brittle. On the Uranium note, unless you want a higher chance of developing malignant tumours I'd stay well clear.

You could use just Tungsten. It is the third or fourth most dence material known to man (I think), and is pretty hard. You could then have a carbide coating which would be posible to recoat when required.

Should you not have to money to buy a significant fraction of the world's total tungsten content, you could always use ceramic balls. There are many different ceramics, I'm sure some are really expensive for one reason or another.

[shadowpyro]

Heh heh so much for that creative notion!
...Though i dont recall tungsten being that rare! -or is it?
ceramics balls are rather efficient, though the ones ive heard of are very small.

[Plays with Fire]

Money no object, posible!!! but unless you are a millionaire I'd look else where.

it was a question to provoke thought and conversation and satisfy my curiousity. obviously, i have a cash flow limited by a lot of factors, but I mean the absolute best...if you literally had one trillion dollars and you could only buy milling media that can never be sold, what would it be?

I like your tungsten idea...

EDIT: tungsten's density is 19.25g/cm3; lead's is 11.34g/cm3

Edited by Plays with Fire, 14 August 2006 - 03:22 AM.

[Andrew]

I know of very big ceramic balls.

The coating the Tungsten Balls idea is a good idea thanks!!! lol. Although I'm sure it has already been done.

We use about 50 thousand tonnes of it a year, compair that to 5 million tonnes of Silicon per year. Granted Silicon is the second most abundant element on the planet, but it's not as if Tungsten is on any similar standing. It's not rare, just it's not overly abundant. Half as abundant as Uranium.

Estimated abundance in the crust is just 0.000125%
Uranium is just 0.00027%
Oxygen is 47%


I recon that the most exotic and expensive Milling balls would be made from Francium. After just 22 minutes they would be half the size.