Ball Mill Safety?

[FieryCreations]

Hi all. Getting into rocketry and just bought a 6lb dual drum ball mill. After reading through this site I'm concerned about having the proper safety knowledge for this and I have some questions.

First off, am I completely stupid for considering ball milling in my backyard in a residential neighborhood? It sounds like if done correctly it's fairly safe, but not 100%, and you should barricade your mill and operate it from a distance. I could stack bricks or concrete bags around it in the back but a sidewalk is about 50' away (through the fence).

For a mill this size, what kind of BP explosion are we talking about? Enough to be a safety concern for harming someone even if properly barricaded? Shake the neighbors hours, get the cops called, etc.?

I've continually read on this site that you should never mill a metal (or any components together outside of BP). The site I bought my mill from says use lead media only if milling rocket propellant. KNO3 is metal...? So you shouldn't actually mill it?

Is there some sort of down and dirty guide of what is and isn't ok? I wanted to get into pyrotechnics and make flash powder and all the other fun stuff, but every day I read about a big no-no I probably would have done if I hadn't read it. This sounds like a case of "You don't know what you don't know" and I want to be safe.


Thanks. 

 

 

[MicroGram]

I'm not going to tell you what is safe or not regarding the proximity to public and stuff because I'm not qualified to do so. However if you do decide to set up your mill I'd stay away from bricks/concrete for a barrier. Just more potential shrapnel IMO. Sand bags would be way better. That's what I use. I've got the same small mill.

Regarding size of explosion if something goes wrong, there's a member here named BurritoBandito who basically almost blew his hand off from shaking one of those 3lb rubber jars with BP in it. He was using glass marbles and its suspected the force of the marbles hitting each other with BP grains in between ignited it. You can read the whole thing here on the forum. Pictures and all; it's not pretty.

I'm not an authority on any of this stuff but I never mill any mixed chems/comps besides BP and I use hardened lead media for BP. Not milling metals its referring to milling actual metals, like aluminum, magnesium etc because of the danger of a pyrophoric reaction. Basically it can ignite/explode when you open the container allowing air in. Potassium nitrate while having potassium in its name is an inorganic salt, and totally fine to mill.

Also if possible install a remote switch for the mill instead of just straight unplugging it. If you unplug it the device is no longer grounded.

Edited December 8, 2023 by MicroGram

[FieryCreations]

Thanks for the reply and advice- Sandbags are easier anyway. Good point, last thing I want is a cinderblock going through my fence into a house or vehicle. 

It's hard for me to picture the magnitude of that explosion. Anything you can compare it to? A large caliber gunshot? M67 frag? It sounds like he was milling by hand for some reason with glass marbled? I'm not screwing around with anything but lead media in a mill a company constructed.

 The ONLY thing I'd like to mill together (beside BP) is rocket candy, but I'm seeing conflicting info on whether that is a death sentence or completely ok. KNO3+fuel should be pretty safe from impact/friction ignition right?

 

Is the rule for not milling metals referring to compositions, or that any SINGLE metal by itself can self ignite? Meaning I cannot mill my pure chunky aluminum down to fine powder? 
 

Edited December 8, 2023 by FieryCreations

[cmjlab]

For milling you want non-sparking media if anything you are milling is flammable (B.P., or B.P. based stars without metal, Rocket Candy, etc); OR becomes pyrophoric when finely milled (Magnesium, Mg/Al, Titanium, Aluminum, etc).

Lead media is one of the generally agreed on, truly non-sparking media.  But it won't work, or won't work well, for milling metals (which carries a great many other risks and isn't recommended), because it's too soft.

Lead media will work perfectly for B.P. and Rocket Candy propellant.  One drawback of lead media is that it slowly breaks down over time tinting light colored chemicals a grey, but it's more of a visual flaw, not really a practical issue (though you probably shouldn't be inhaling lots of smoke that contains the lead for obvious reasons).

There are other media which are supposedly non-sparking, and which have pros and cons, but generally speaking Lead is the right media to use for beginners IMO.

BLUF - Ball mill safety is something you need to read up on, then adhere to generally safe practices, and ask questions for what you don't know (like you did here). The more safety precautions you add, the less likely an issue happens, and the less likely of injury or death of something does happen. 

Some precautions are: keeping people away, milling single component chemicals, non-sparking media, remote turn on/off milling machine, barrier for your mill, remote placement of your mill (find somewhere remote to mill and bring a power source), using jars that are well sealed during use, etc.

Ball mill safety is something where you always plan for the worst.  Though real works mill explosions are infrequent, i believe they occurred because of complacency leading to cutting of corners to save money, save time, etc.  for example, milling with marbles leads to glass shards being broken off into your comp.  If that comp is an already flammable comp, like B.P., you just added a friction sensitizer to it.  If it's something like single component chemicals, where milling it with marbles doesn't present an issue at the time, you still added a friction sensitizer to something that will be combined later and increase risk of an accident.  Another milling incident happened because of milling metals which becomes pyrophoric and when the jar was opened and emptied and the inevitable could of fine metal dust floats around, either the oxygen caused spontaneous combustion OR the stainless media bouncing off each other created a spark or friction enough to ignite the cloud of metal floating around (i.e. fuel/air explosion).  

Hope this helps some.

[Arthur]

The presence of lead in BP is a marker for home made powder. 

[Guest]

2 hours ago, Arthur said:

The presence of lead in BP is a marker for home made powder. 

You would then suggest what? Brass at $1 a piece? Or maybe zinc?

Zinc melts @ 786F. I believe my lead pot can reach 800 or 900F.

Edited December 9, 2023 by Bbqjoe

[FieryCreations]

4 hours ago, Arthur said:

The presence of lead in BP is a marker for home made powder. 

A marker? Am I supposed to be worried someone knows I'm making BP?

[Arthur]

Whether it matters depends on where you live in the world. Ask a California resident and a Nevada resident. The state boundary line marks massive changes in the regulation of DIY/ possession/ powder etc. Real commercial BP has no lead content, DIY powder using lead balls contains easily detectable amounts of lead.

If you live where DIY BP is totally OK legally then it doesn't matter.

[FieryCreations]

14 hours ago, Arthur said:

Whether it matters depends on where you live in the world. Ask a California resident and a Nevada resident. The state boundary line marks massive changes in the regulation of DIY/ possession/ powder etc. Real commercial BP has no lead content, DIY powder using lead balls contains easily detectable amounts of lead.

If you live where DIY BP is totally OK legally then it doesn't matter.

Oh. Yeah I'm not messing with anything I'm not supposed to be. I moved to a free state for that very reason.

So is it 100% not ok to mill any metal like aluminum by itself? I bought a bunch thinking I could do that as long as it wasn't mixed with anything else. 

 

And just to confirm, KNO3/sugar mixtures are ok to mill together with lead media? Pretty much that and BP are it? I'm still unclear if that response saying rocket candy as ok meant individual components or after mixing. 

Edited December 10, 2023 by FieryCreations

[cmjlab]

Yes you can mill KNO3 and sugar together using lead / non-sparking media.

Milling metals is dangerous (edit*: when I refer to milling metals, yes I mean just milling AL by itself is dangerous)  You need to understand what pyrophoricity is, and how to avoid it, as well as how to take precautions in case you open the jar and the metal ignites because of pyrophoricity.  Some examples are a welders apron, long sleeve cotton apparel, thick work boots, a welders helmet / full face shield, and welders gloves, remote starting & stopping your mill, cracking the seal slowly and leaving the mill jar alone to allow slow influx of fresh air, etc..  Without understanding why some those things are needed, it is NOT a good idea to mill metals on your own.  

Additionally, it is cheaper to buy milled metals than it is to make them.  It takes a long time to mill Aluminum down to "dark" pyro grade (3-4 weeks).  I'm not even sure that lead would be hard enough to mill it down without significant wearing of your media.  

Edited December 10, 2023 by cmjlab

[cmjlab]

That's my the extent of my understanding of milling metals.  What you do is up to you.

[FieryCreations]

Whoa ok, even if I wanted to learn and get all the proper techniques down I'm not trying to run something for that long. 

Thanks for the replies! 

[Richtee]

You cannot mill anything that’s harder than your media efficiently- not to mention the other hazards.

[DavidF]

Is the 6lb dual drum ball mill a rock tumbler with the rubber jars? If so, it won't run two jars when using lead media. Also, it would benefit from being sped up to mill faster. Folks do that by increasing the diameter of the drive roller. My guess on the result of an accidental ignition on one of these baby mills would be a large poof or maybe a 'whoomp', a large puff of smoke, and lead balls all over the ground near the mill.

[Arthur]

The "Black" of dark aluminium is likely the small amount if charcoal added to scavenge oxygen in the jar as more open aluminium surface is exposed. However simply don't play with aluminium and ball mills together to avoid fires.

[FieryCreations]

On 12/10/2023 at 12:06 PM, DavidF said:

Is the 6lb dual drum ball mill a rock tumbler with the rubber jars? If so, it won't run two jars when using lead media. Also, it would benefit from being sped up to mill faster. Folks do that by increasing the diameter of the drive roller. My guess on the result of an accidental ignition on one of these baby mills would be a large poof or maybe a 'whoomp', a large puff of smoke, and lead balls all over the ground near the mill.

I bought it from a chem site specifically for milling powders. It's supposed to run both jars. They are sealed water tight.

[DavidF]

Well, if the site says it can run both jars, each one half full of lead media, then you're good. The 6 lb tumblers commonly used by hobbyists can't. They can run 2 jars with rocks and water. They can run 2 jars with ceramic media and powder. 

[Arthur]

I doubt that the mill will properly turn two loaded drums with lead media. Look for Alumina media or zirconia media, both hard and robust and much lighter than lead. 

inoxia.co.uk/products/ball-mill/media/ceramic-balls-20mm  Yes he ships if you cannot find alumina media locally.

[FieryCreations]

https://unitednuclear.com/ball-mills-c-25_35/6-lb-capacity-ball-mill-p-607.html

Did I get screwed? It says simultaneously run two barrels and each requires 100 balls of 1/2" lead.

Each barrel is about 1/4 loaded with the amount of media they say to use and it seems to turn fine. Can't comment on the final product since I haven't put up my sandbags yet to run a full load of BP. 
 

Edited December 12, 2023 by FieryCreations

[DavidF]

Maybe not 'screwed', but the general rule most pyros use is to fill the jar 1/2 full of media with 1/4 load of powder and 1/4 'air'. I was basing my comments on that. The guy in the toilet paper BP thread is using 2 jars but with brass media (expensive! But not as expensive as zirconia). He's probably using less than half full jars of media, I suspect. 1/4 jar of lead might be just fine but take quite a bit longer.

[FieryCreations]

1 hour ago, DavidF said:

Maybe not 'screwed', but the general rule most pyros use is to fill the jar 1/2 full of media with 1/4 load of powder and 1/4 'air'. I was basing my comments on that. The guy in the toilet paper BP thread is using 2 jars but with brass media (expensive! But not as expensive as zirconia). He's probably using less than half full jars of media, I suspect. 1/4 jar of lead might be just fine but take quite a bit longer.

In that order? Meaning after the media, you fit in as much as you can in the gaps until only 1/4 of the jar is air?



Ok so I know doing this in a garage isn't advised or ideal, but it seems like people do it. I feel like it may be safer than in my yard especially with rain and snow coming.


If I did it in my garage what is the biggest danger if I encase it in sandbags? Would it be the resulting fire from an explosion? Definitely remove fuel sources. I'm guessing I should also extinguish the pilot light on my water heater? 

[DavidF]

Lots of folks mill lots of different ways. 10 pyros will have 12 opinions on it. One general rule is to fill the jar half full of media, and powder until it just covers the media, and leave the rest empty. I don't think anybody here would say milling in a garage is a good idea. There is a lot of ball mill talk on this forum in old threads. Reading through those old threads will help give a better feel for what other pyros do. The biggest problem with milling in a garage is the risk of fire if it ignites, and the next biggest problem (if there's no fire) is the slimy, stinky fart-smelling residue that will be all over everything.

[FieryCreations]

Appreciate the replies. If I do it I'll be as safe as possible and wont make it a regular habit. 

[FieryCreations]

Wow. They sold me a "ball mill" that looks like it's the identical rock tumbler from harbor freight with their sticker on it hahaha

[Guest]

IMO, I think ball milling simple, non reactive ingredients in your garage is just as safe as doing a deep fried turkey in there on Thanksgiving.

Some folks know exactly what they're doing, others listen to people who don't, and burn their house down.

If you feel a lack of information, don't ever put all your eggs in the same basket.