Making a mold for spherical ball mill media

[markx]

I had alot of scrap lead lying around (leftovers from "scrap metal age" )so I decided to cast my own spherical media for the ball mill. It turned out very good and I would like to share my method with the rest of the community. Also I can't remember having encountered a thread that describes the mold-making and casting process in detail, so i'll post my method.

 

First you take some play-doh or plasticine and form a number of spheres with suitable dimensions out of that material. They don't have to be perfectly round. In my case I made 14 of them (that's how many slots the final cast mold is going to have):

http://i111.photobucket.com/albums/n155/markx_01/IMG_0428.jpg

 

Then take a vessel into which the mold will be cast. I used the bottom part of a 5L PP canister:

 

http://i111.photobucket.com/albums/n155/markx_01/IMG_0429.jpg

 

Pour dry plaster powder into the mold and mix with water to form the slurry:

 

http://i111.photobucket.com/albums/n155/markx_01/IMG_0431.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0432.jpg

 

Now take the placticine spheres and tuck them halfway into the wet plaster mixture. Try to get them excactly halfway into the plaster because otherwise you will have trouble separating the mold parts. This step has to be performed rather swiftly because the plaster tends to set quickly, especially in colder environments:

 

http://i111.photobucket.com/albums/n155/markx_01/IMG_0433.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0434.jpg

 

Stick a couple of nails or pieces of metal wire into the bottom half of the mold too. They will serve as guidance rods to fit the mold halves correctly together afterwards:

http://i111.photobucket.com/albums/n155/markx_01/IMG_0435.jpg

 

Now let the plaster cure (about 30min). The bottom half of the cast mold is complete. The upper half will be formed out of a second batch of plaster poured over the bottom half. But to be able to separate the mold halves you have to apply a layer of separating substance between them before the upper half is cast.

 

I used spray-on mold wax, but linseed oil or lacquer also works fine:

 

http://i111.photobucket.com/albums/n155/markx_01/IMG_0440.jpg

 

Now a second batch of plaster is prepared and cast over the bottom half:

http://i111.photobucket.com/albums/n155/markx_01/IMG_0443.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0444.jpg

 

After the plaster has cured the mold is carefully separated from the plastic:

http://i111.photobucket.com/albums/n155/markx_01/IMG_0446.jpg

 

The two halves are separated by forcing a knife blade between them. Avoid excessive force in this step as the plaster may break and ruin the mold:

http://i111.photobucket.com/albums/n155/markx_01/IMG_0447.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0448.jpg

 

Now the cast mold is almost complete. The only operation left is to drill the holes through which the molten metal can reach the recess:

http://i111.photobucket.com/albums/n155/markx_01/IMG_0463.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0464.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0465.jpg

 

That's it.....the mold is complete

 

Now just melt the lead, assemble the mold and secure the halves with a string or wire and pour the metal into the mold (be sure to perform this step under proper ventilation as lead fumes are very poisonous):

http://i111.photobucket.com/albums/n155/markx_01/IMG_0467.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0468.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0469.jpg

http://i111.photobucket.com/albums/n155/markx_01/IMG_0471.jpg

 

The lead media needs some deburring before it can be used in the mill but besides that the method works just great. You can cast as much media as you need and by making your own mold you can adjust the dimensions of the media freely.

 

Hope it is of some use to anyone

[ewest]

Excellent tutorial! The simplest ideas are the most amazing, and I was really wondering if you could use plaster to cast lead.

 

I got some media thru mail order but they were cylinders and the only way I could think that they made them was to take a plaster slab and bore some 1/2"od holes about 1/2" deep then fill with lead. And your tutorial just confirms to me that it would work.

 

Good job.

[moonshot]

Yes very good tutorial. Practical in that it uses inexpensive and readily obtainable materials and the process is simple enough for us amateur pyros. Great idea! Thanks for sharing that one.

[FrankRizzo]

ewest,

 

If you got 'em from Matt, I believe he drills a bunch of holes down the center of a 2x4, then uses a table saw to rip it in half down the centerline. Some clamps are used to hold both halves together, and then lead is poured into each cavity along the length. When the lead has cooled, the clamps are removed and the two halves are separated. Each 2x4 can be used 3-4 times before the holes have enlarged too much from burning.

[asilentbob]

I'm surprised that plaster and even wood can take that kinda heat, but yeah, thats way cool.

[ewest]

ewest,

 

If you got 'em from Matt

Yes, I sure did. And like asilentbob said, I'm surprised wood could take that kind of heat without burning.

 

One thing I WILL be using this tutorial for is to make molds of golf balls for my Golf Ball cannon. A nice little pile of lead cannon balls would make a nice conversation piece

[Aquarius]

Another option is to use a round bullet mold to cast lead media, I got a double that makes two 0.6 inch round balls. Availiable at most wellstocked gunshops, as well as on the web. I tried the same method as above using glass marbles, and it worked, but not as easy to remove as the play-dough...

[fight fire with fire]

Good tutorial!

 

I'm still really surprised that plaster can withstand the heat from the lead. Did the plaster errode slightly from the heat?

 

 

Henry

[FrankRizzo]

Yes, I sure did.  And like asilentbob said, I'm surprised wood could take that kind of heat without burning.

 

One thing I WILL be using this tutorial for is to make molds of golf balls for my Golf Ball cannon.  A nice little pile of lead cannon balls would make a nice conversation piece 

Hmm...great idea >

 

About the wood: It does char each time you pour lead into the cavities, which is why you only have 3 or 4 times of usage before the cavities become too oversized. The wood molds are disposable and can be used for charcoal afterward.

[Xtreme Pyro]

Awesome tut! thanks this could come in someday

[markx]

I'm still really surprised that plaster can withstand the heat from the lead. Did the plaster errode slightly from the heat?

 

The heat from molten lead is not that huge anyway, but sure, the plaster mold will not last for ever. Although it takes the abuse very well. A single slot is good for at least 15 castings, so you can make about 2 medium sized mill jars worth of media with a 14 slot mold like mine. Just make sure to dry the mold completely before you pour any lead in. Otherwise the expanding water vapour cracks the slots quickly.

[fight fire with fire]

OK

 

 

this is pretty cheap to make though you could yank the rods out and make a new mold i would have thought.

[kwinchee]

Hay man

good work on the tut I just made up a mould today using your Idea but I live in a small town so I used linseed Oil no drama's and 5c gobstoppers as the balls.

 

I will melt down an arsenal of old car battarys in a few days make some sinkers and media. For my little 3lb'er rocktumbler which is due to arrive any day as my home made ball mill burnt out and i cbf making a new 1.

 

 

Cheers

 

AUSTRALIA LAND OF THE FREE to not go outside

[lja]

Nice tutorial!

 

You should cast a set of media and leave all the extra lead attached. This way when you need to make another mold you can use those castings instead of the playdough balls. You'll save yourself the trouble of drilling all the pouring holes again.

[aquaman]

I've been wanting to do this for a while now but never had the time or even knew if it would work. Nice tutorial!

[Svarc]

Nice one. But you can't make smaller lead balls with this setup, or you can?

This is my way (just for information) :

I first make round barrs (cilinders) of lead, then cut them in pices (long as wide) and then roll bunch of them between two hard surfaces. You can make lead balls of every diameter (like i want to use in my ball mill mix of diferent diameter balls and some cilinders for beter beating) It is verry time consuming and work consuming way to make lead balls but it has less preparing than your setup. Just drill a holes in wood, melt lead, pour it in the holes, cut the wood, get the lead cilinders out, cut them with scissors, place between one fixed hard surface and get piece of thicker hard plate and roll them up. I managed just yesterday to make almost 2kg of 5mm lead balls in 1 hour.

 

But I still think that I will use your way next time because I still have hard pain in my hands from rolling.

[pyrogeorge]

Nice tutorial!i will make my media soon..

[Ventsi]

Here's a handful of questions:

I'm just wondering, does the mold need any type of lubrication/release agent before the lead is poured in?

Also what consistency should the plaster be made to before starting to work the actual mold? How long does such a piece take to completely dry/cure. Can I speed it up by putting them in the oven, max. temperature?

 

Also, can this stuff handle casting molten aluminum?

Edited January 21, 2010 by Ventsi

[pudidotdk]

It should not be lubricated prior pouring the metal. The plaster may harden quickly depending on what type you are using. I have found alabaster plaster to cure rather quickly, which has to be worked fast. Follow the plaster:water mixture on the package. You can pour aluminium in, but make sure there is absolutely no water in the plaster when doing so or it could mess up the casting and spray molten aluminium. You can dry it in the oven, but I have had cracks if heating too quickly.

[gordohigh]

Wouldn't you need to pre-heat the mold beefore casting aluminum? The higher temps required to melt alu would probably cause a failure without properly pre-heating I would think. I was bored one day and actually melted about 40~50 coke cans and was surprised by how much I got. I actually chucked it in my lathe and wound up with enough to build a star plate, although I haven't completed it yet. Pretty good quality too once you get a half an inch or so below the slag line.

[pudidotdk]

I have not had much succes only aluminium cans. They have a rather large surface area and tend to oxidize rather that melt.

Starting with some aluminium chunks and melting it in the crucible until you have a nice little pool have reduced the oxidation, and the aluminium came out fine when cooled.

[gordohigh]

Yes, I did melt some aluminum stock first to form a nice 3~4 inches on the bottom and the cans were crushed before inserting. The first few cans did oxidise quite a bit and produced some nasty smoke.

 

As I said, I was bored and wanted to try this once, the metal quality was not as good as I first thought and broke easily when machining so in the end I scrapped it.

 

On the other hand, I did make some lead media with an alu star plate although It would have been easier with some of these other methods. I recently found my old cooler with all my lead and molds, pots and ladles and have an egg sinker mold with 8 sinkers each of 2 different sizes that I plan on trying. It's always nice to see all the creative thinking going on here though as doing these things with hardware store items is always fun for the experience and many do not have access to anything else.

 

BTW, nice tutorial with pics!!