272 replies to this topic

[shadowpyro]

Wow! whoever using those media would get a huge shock when they got back!

on the subject of ceramic milling media, what size are your ceramic balls? (not goin there!)-or more to the point, what size woul dbe most appropriate for ceramic milling media? as the last i remeber ceramicware is rather low in density...

Edited by shadowpyro, 15 August 2006 - 05:53 PM.

[Andrew]

I use 20mm ball for my mills upto 6 litres, and 40mm balls for the jars above 6L in volume.

There is a rather interesting thing about the density of the ceramic balls I use. It works out that 1kg of balls take up about 1/2 litres of volume in their most compact arrangment. This means calculations are really simple for the amount of milling media required. A 3L jar needs 3kg of ceramic media to half fill it.

Lead works out at about 3kg per Litre of mill jar volume.

The other consideration that has to be made is the poor motor that is meant to turn all this media in the jar. For ceramic media in a 6L jar (i.e. 6kg of media and either 2.5kg of a salt, 800g of bp or 200g-600g of something hard to grind up) a 250W motor just about surfices. If I were to use Lead media I would need a 750W motor, and 1hp motors are pretty heavty and expensive. If Tungsten media were to be used you would need a 2hp motor for a 6L jar.

[EnigmaticBiker]

In my search for cheapest pyro tools/materials, something occurred to me last night.

I found some unused imperial sockets which might make useful milling media.

Chrome vanadium hardened steel should work well for single materials, even metals.
(I'll assume they will produce some sparks, so no compositions)

Guessing that powders trapped within them will move in and out as they are used.

[Spudgun]

Is 10mm brass rod too small?
I would be using it inside one of the 1.3L inoxia jars
I don't know why Im asking this actually because I've just gone and bought a load of it, o well...

[EnigmaticBiker]

Is 10mm brass rod too small?
I would be using it inside one of the 1.3L inoxia jars
I don't know why Im asking this actually because I've just gone and bought a load of it, o well...

Seems a bit small, the smallest diameter I've heard of being about 12mm (on this thread). It'll probably still work for most materials, just inefficient.

Update on the Chrome socket idea, it mills Al foil and tough AlMg alloy fairly well with very little wear to the sockets; only scuffed after about 2 days use.

[Wyvern]

i found these solid brass bars on ebay the today, much better than filling pipes with lead

http://stores.ebay.c...9QQftidZ2QQtZkm

Edited by Wyvern, 30 November 2006 - 07:13 PM.

[hoarp001]

Silicone casting rubber can take the heat of molten lead. (sounds stupid, but it can)

You could get some appropriately sizzed ball bearings, epoxy a stick onto them, hang them upsie down above an old lunchbox or something and pour silicone into it. Then all you have to do is remove the ball bearings and pour the lead into the hole at the top...

You could make a re-usable mould that could make 10 at a time...

This rubber on the tiranti site is suitable...

Rubber
The site

[cooperman435]

If anyone is still wanting milling media in the uk I have now made myself the tooling to make my own lead ball castings.

PM me if you want some .

I can do 1, 2, 3 and 4 ounce balls in quite large numbers

(1oz = 17mm, 2oz = 21mm, 3oz = 24mm and 4oz = 26mm)


Its cheaper to make them from straight lead but I could do them in hardened lead if really neccecery. Im using straight lead and the wear on them is tiny if at all after weeks of milling.

Hope this helps someone.

[lew]

I too have just started casting my own media.

I have quite a large mill. its 15 litres with a hexagonal rubber insert.

So far i have made 50 2oz lead balls that i have used for milling BP and they work very well.

I have also made some 'jacketed' media for grinding harder single chems.

I got a length of 22mm copper pipe and cut off about 50 1 inch sections (using a pipe cutter). i then stood these upright on a sheet of tinfoil (on a concrete floor) and poured moltern lead into them. these should last longer because of the harder copper jacket.

I went to my local scrap yard and enquired about lead. I dont know how much it was, but i said to the guy "how much can i have for £20". I came away with a sack i could barley carry. It must of been well over 40 kilos!! enough to make media to last for decades!!!

[Steve]

I use 20mm ball for my mills upto 6 litres, and 40mm balls for the jars above 6L in volume.

I don't think the volume of the jars has any real relivence on suitable media size, it's really down to jar diameter.
Firstly I need to say that I have not run trials with different media in different jars and compared efficiency with time. My reccomendations are based entirely on placing balls in jars and watching how they move as the jar is rotated, assuming the ideal system would be the largest balls that still tumble easily without getting too jammed up as they try to turn over.
This is what I reccomend

100mm Jar : 20mm balls (Inoxia 1.3L ball mill jars)
200mm Jar : 30mm balls (This is the OD of my 3 and 6 litre jars)
275mm Jar : 40mm balls (This is the OD of my 10, 15 and 20 litre jars)

I know a range would be more ideal information but I've only worked with those 3 diameters so I don't know where the cutoffs are, I'm sure you can extrapolate the data yourselves.

Also, if you are planning a new mill, don't underestimate the help that getting a sheet of paper and a compass:
Draw a large circle equal to the ID of your intended Jar
Set the compass to the size of your intended ball and draw lots of circles, making sure you don't overlapp previously drawn balls and you don't try to order it too much. I have used this method before when trying to visulise the jar and it really helps. Also good for tubes.

[Caramanos2000]

I found, at a bakery supply store some 3/4" Ceramic Balls. There is close to 1 pound of them, there is allot, almost enough to fill a 3Lb jar completely. It was only about $5 US, I am testing them out on some sulfur.

[TheExplosionist]

Compiled from the combined knowledge of the internet forums and rec.pyrotechnics:

According to rec.pyrotechnics : ( 1 / 10th of jar diameter is reccommended by Lloyd Sponenburgh)
100mm Jar : 10mm balls (Inoxia 1.3L ball mill jars)
200mm Jar : 20mm balls (This is the OD of my 3 and 6 litre jars)
275mm Jar : 27.5mm balls (This is the OD of my 10, 15 and 20 litre jars)

- lead balls are dense but soft (>11g/cm3) and non sparking
- stainless steel balls lighter than lead but harder and non sparking
- ceramic balls harder still but lightest of all and non sparking
- mild steel rod is softer than stainless and sparking but is much cheaper
- brass rod is softer than steel but denser and non sparking

Heavier, denser media will have more impact energy and so will be able to grind course/tough materials.
Harder media will theoretically be able to grind materials finer than soft media because as media are impacted upon they deform at the microscopic level. Media that is deformed will have a greater surface area reducing the impact pressure.

For blackpowder anything that is sparkless is fine. For non-ferrous such as alumnium extremely hard media is desirable.
For aluminium heavy, spherical media that is very hard is preferable. According to one source 3/4" stainless steel will suffice, another suggests anything less than 1.5" is hopeless. The use of any other kind of media for grinding aluminium is unknown.

Regarding the use of brass or steel tubes filled with lead to gain the best qualities of each material:
It is not recommended.
The lead will not bond to the tube for long, even if the following are attempted:
1 - Attempting to internally thread steel/brass tubes to hold the lead. This is reported to not work.
2 - Bending in the ends of the tube to stop the lead falling out is doubtful.

[Steve]

According to rec.pyrotechnics : ( 1 / 10th of jar diameter is reccommended by Lloyd Sponenburgh)

What type of media is he using here though, becuse I would of thought that you would need a bigger ceramic ball than lead ball, shearly from a density point of view. A 10mm lead ball could have some weight and crushing power, but a 10mm ceramic ball is a measly little thing that doesn't seem heavy enought for the job.

[Caramanos2000]

If I were to use those .50 cal lead round balls for muskets how many would I need for a 3lb barrel?

[Mumbles]

I have 100, and it's a bit undercharged. 200 balls should do the trick with some to spare.