Author Topic: Ball Mills & Gear  (Read 545 times)

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Offline Bismuth

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Ball Mills & Gear
« on: January 25, 2014, 09:20:11 AM »
My thumlers tumbler I inherited from my grandfather who genuinely used it for gem polishing is coming to the end of its life. It's time to salvage the motor for a star-roller and build a bigger, more optimised ball mill. I looked at buying another one but they are pretty expensive for what they are and I just don't want the motor near the jar anymore.

So I am going to build one. I'm going to try out that new http://www.stainlesstumblingmedia.com/rebel-17-drum.html drums. PVC is loud, and I've always had clumping issues living in at the bottom end of Australia and these are meant to help with the rubber liner.

Looking at getting a thermally protected motor, and building an enclosure for it.

My question right now is what do people use for media? I used a combination of brass bearings and lead fishing sinkers. Some people say that fishing sinkers are crap because they erode quite easily if they're not hardened. I'm not sure if the sinkers I got are a different story or my rpm being so low made it not an issues/drum size, but they always worked for me. 5 years and not noticeable wear.



However, with an optimised system and larger 15lb drum I might have an issue so I'm all ears for a better alternative. What are people using?

Offline leedrill

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Re: Ball Mills & Gear
« Reply #1 on: January 25, 2014, 01:20:47 PM »
i will say i bought 20lb of lead media of leadballs on apc he was a pleasure to deal with and happy to help us aussies his media i can say is truley amazing its hard to beleive its lead i even tried hitting a sacrificial one with a hammer and ill be honest its crazy hard for something that is lead hard i will say go that option with out a doubt but 20lb is just under what is needed for a 1 gallon 3.785L drum so depending on the volume needed its not a cheap option

well it is almost the cheapest option apart from brass rod or brass or copper lead filled tube

this would be cheaper but bloody shipping for 20lb of lead was like $60 so

hope this helps to you finding the cheapest option but bismuth its hard to go past this lead

Offline ANARCHY_08

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Re: Ball Mills & Gear
« Reply #2 on: January 25, 2014, 06:08:13 PM »
well, you are a pyro, soo you dont mind spending your time on misc hobbies.
go to Tyre places and gather their old wheel weights, they get a 10L+ bucket easily per day. sort through them with a magnet and sort out the steel/zinc misc ones and the rest will be lead. go on ebay and buy a set of ball fishing sinker cast plates. youll also get to quench them this way.

this will be your cheapest and least time consuming way for decent media, brass media for larger jars will bankrupt you.
I went down the 'cast lead into brass tube' way and it took forever to cut, even with an electric metal bandsaw. excluding the brass tube I made 19 Kg of lead ingots from wheel weights that cost me nothing. in my 2 mill jars I can make a total of 1.4 kilos of bp in 40 mins. that will give you something to strive for.

as for the rest of the components, your going to build one so go heavy (you have a wasp) 16mm steel rods(heater hose will fit for rubber rollers that way) heavy pillow block bearing and a nice 1/4 horsepower motor. 
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Offline leedrill

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Re: Ball Mills & Gear
« Reply #3 on: January 25, 2014, 07:01:27 PM »
^^^^^^^^^what he said   $114 + $60.   that was the price for 19lb of steve {leadballs media }  so its not cheap at $6 a lb   but if there was no shipping id never consider making it my self to be honest but if you do make it your self do as steve does and quench it in ice water he has told me is the secret to getting the hardness he obtains with the ingots he uses the little bit of antimony and ice water goes a long way

but i digress who is really indeed of it i mean with anarchys setup im sure the media will be lucky to see more than 2000hours in his life and will probably last that long too i mean 2000 hours means if he left the bp in for 1 hour he would have 2800kg of bp id like to say ill use that much in a life time but holy crap ill need a bigger shed haha so yeah

the hardest lead possible is not really a factor just the hardest you can make

Offline Bismuth

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Re: Ball Mills & Gear
« Reply #4 on: January 25, 2014, 09:50:10 PM »
I need 35lbs of media to half fill one of those drums for a model B thumler tumbler so I'm told.

Thanks Anarchy, and I've seen what you did with your ball mill in the tutorial section so it'll end up looking similar to that. That roller idea was nice.

I'll ask to see how much it costs to get the hardened lead from "leadballs", leedrill. I have a decent chunk of lead at work which can help me meet the quota but I'm not sure if I can be stuffed adding casting to my project list. I'm still waiting to finish my press, damn it. I might end up trying both since I have about 5kg of lead, and two drums to fill. I personally never want to use ceramic.

Drums have been ordered so will do a photo tutorial when it all comes together.

Offline Jessoman

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Re: Ball Mills & Gear
« Reply #5 on: January 25, 2014, 11:55:23 PM »
I also can vouch for Steve aka leadballs around 20lbs for $174. Extremely solid media! Highly recommended and he's very professional.
Jess

Offline JayDee2

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Re: Ball Mills & Gear
« Reply #6 on: January 26, 2014, 10:48:44 PM »
I use 2 standard 4 inch Loretone barrels running at 80RPM and Zirconia is my media of choice, after experiencing horrendous wear rate using hardened lead from Pyrocreations.  Zero wear with the Zirconia to date. It's about 75 percent the density of lead and I use the same milling times as I did with lead. 2 small barrels of Zirconia was affordable (just), but anything larger would soon become prohibitedly expensive   :-[

Not sure if the problems I had with lead  was just crap lead, or whether the 80RPM rotation really worked the lead to its limit.

Offline Bismuth

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Re: Ball Mills & Gear
« Reply #7 on: January 27, 2014, 09:48:22 PM »
Yikes! I'm surprised at the rate of wear some people are finding on lead. I find it bizarre I have been using fishing sinkers without noticing any wear at all. At least, compared to the 1/2" brass bearings that run with them, they at least erode at an equal rate.

I found a post on fireworking by Ned who records his results for his wear as:

Start, 0.50" diameter, 11.58 grams per ball

9/11/12, 0.495" diameter, 11 g each

12/11/13, 0.485", 10.4 g each


with Steve Young's media. Given, since emailing Steve, he told me he adds an additional 2.5% antimony to lead media going international since his "warranty" (he'll re-cast the media at 1/2 cost when balls reach <10g) is not financially viable to take on-board. Ned would use his mill more than any of us ever would in a year, but it doesn't seem like it's a life-time with the standard alloy.

On the other hand, brass is too expensive. I just don't feel comfortable using ceramic from documented accidents where they have been a common factor. Stainless steel is used by some, but people fear that its impacts are too hard with one another. Never thought you could hit black powder with enough force to ignite, but I don't fancy being the first person to prove that wrong when milling.

Offline JayDee2

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Re: Ball Mills & Gear
« Reply #8 on: January 28, 2014, 08:13:46 PM »
Bismuth, can you send me any links to accidents related to ceramic media?  Was the media normal ceramic as sold by a few of the pyro suppliers,  or Zirconia?  Obviously I am interested !!!!!!!
Cheers,
Jay

Offline Bismuth

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Re: Ball Mills & Gear
« Reply #9 on: January 28, 2014, 09:10:08 PM »
Hi Jay,

No accidents have struck me in particular without digging around. Since starting this hobby, rumors of ball mills exploding with the common intersection being that they all used ceramic media have floated around. There is a thread on APC (http://www.amateurpyro.com/forums/topic/8045-how-safe-is-it-to-ball-mill/) where Mumbles vaguely references some occurrences he has heard of. Unfortunately, with the nature of ball mills exploding it is never clear why they exploded. It may be powder falling into the motor or accumulating, residual metal in the charcoal source or whatever.

There's an article on Passfire that delves into ball mill media. I'm going to take an excerpt from it in regards to the safety of ceramic media. Not within the rules, but for the matter of safety, I'd be surprised if someone cared. 

The most commonly raised concern about milling with ceramic media is the risk of sparking. There are many types of ceramic media, and some may contain silica particles which could produce sparks, but for the most part this is not a problem. The key is to know the type of media that you have and purchase it from a well known manufacturer such as CoorsTek, who claim that their media does not spark.

Even when using a non-sparking type of ceramic media, milling metals such as titanium or steel could result in impurities becoming lodged in the ceramic pores, contaminating the media with impurities that introduce a sparking hazard. While used ceramic media can be purchased for under $3/lb from some suppliers, the lack of knowledge about prior use would raise concerns in this area.

Another test you can perform is to take your media into a dark room and strike it against each other to check for visible sparks. Some people have reported orange sparks during this test, while others report nothing. Note that some forms of light output known as triboluminescence actually produce "cold sparks" that are incapable of causing accidental ignition. However, any visible sparks should cause concern.


PS. I also found a thread on Passfire where there's a topic of someone who had his mill explode and recently got some new ceramic media (http://www.pyrobin.com/files/img_4008.jpg). I tried to find info on zirconia but didn't find much at all.  Someone asked Lloyd S about it, but he made only the comment that he uses ceramic for individual chemicals, but sticks with lead for milling black powder. Others claim they have been using ceramic for years with no issues. It's one of those topics...

Offline Bismuth

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Re: Ball Mills & Gear
« Reply #10 on: January 28, 2014, 09:35:56 PM »
http://www.pyrobin.com/files/the%20explosion%20of%20a%20ball%20milling%20jar.pdf - good read on what to expect if a mill did explode.

By the way, JayDee, not trying to turn you against your media and make you feel it's unsafe. There are innumerable factors at play here. In that thread on Passfire where a mill exploded, there are many speculations. Some are convinced that powder leaked from the jar. Others believe it is PVC drums due to their static potential. Lloyd seems to think large media may be crossing the line of activation for impact sensitivity. Too many variables at play.

So long as a mill is started from a distance and turned off, with something between it and the operator, then there is no physical danger in the end of the day.

Offline Falcon

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Re: Ball Mills & Gear
« Reply #11 on: January 28, 2014, 11:29:07 PM »
I can add a bit further to the discussion on mills exploding based on my research of gunpowder mnufacture.

The british were fairly concerned about using "fresh" charcoal for grinding into gunpowder. Properly made charcoal can be so reactive it may even sometimes be considered pyrophobic, spontaneously igniting sometimes days after removing from the retort due to oxidation by the air.
The response was to only use charcoal that had been stored in air for at least 10 days before any milling was done. I believe even Mumbles incident on APC involved only charcoal milling, but I'm not sure as to the cause.

Another thing to watch out for is where you obtain the wood for your charcoal. The Swiss powder mill runs their wood and finished charcoal through metal detectors due to the common occurrence of nails in the wood used for charcoal! I would not want to be near a mill that has even 1 nail in it!

As for the general topic, I'm a fan of lead balls, plain and simple. I'm using the same batch of balls I was when I first started my mill and they're still fine. Plus I'm in muzzle loading rifles, so I have all the gear for casting them. As an added benefit, used range lead is free or can be sold for $1/kg at the recyclers; and 1kg of lead is not much! I even once sold over 100kg of melted down range lead!
The only problem for larger capacity mills is it takes hours to cast the many kg's of lead required, and you need good bearings to handle the load, but it doesn't cost anything in shipping as it can all be locally obtained!

It might even be an idea to use a TEFC motor - totally enclosed fan cooled motor, to avoid any dust issues - but that shouldn't be a problem with a proper sealing jar. Just an added safety feature and they don't cost much more than a normal electric motor.

If you want to see how a lead ball spalls off material, place it between two sheets of flat perspex or possibly even glass. Then press down gently and roll the top sheet. This is one way cast balls can be rounded and the casting sprue removed. I know on pure lead the spalling is quite a bit, with little sheets (like foil) peeling away from the edge. I haven't tried this on the hardened lead, but the harden lead in my mill looks the same it did when I started using it. This is fairly hard lead though; roughly 20 Bhn, composed mainly of lead and antimony with some tin (typical scrap range lead)
« Last Edit: January 28, 2014, 11:39:19 PM by Falcon »

Offline Astroboy

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Re: Ball Mills & Gear
« Reply #12 on: January 29, 2014, 07:24:43 PM »
Have a search around eBay, you can usually find 20 mm round sinkers for around $10 kg. An easy way to clean them up is just run them in the mill on their own for a few hours, this also serves to anneal or harden them a little and further milling will close up the holes(can take a while longer), Ive got 2 jars with around 15 kg in each jar which have been in use for a few years now and haven't noticed any major wear. I also have ceramic media that i use for single chems but I only use lead for milling BP as I just don't wont to take the chance with ceramic, also lead is a lot heavier for its diameter and seems to mill faster and I figure less time in the mill reduces risk
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Offline stinger

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Re: Ball Mills & Gear
« Reply #13 on: March 01, 2014, 08:26:38 AM »
I've been milling bp with alumina media from diverse hobbies for 3-4 years. They aren't sold there anymore and i cant remember exactly what it said but it did mention non-sparking in the description. I've dropped them on top of each other from a meter and reviewed in slow-mo footage and they've never sparked so i consider them pretty safe to use in my 160mm jar