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How-to: Metal cannonballs of (nearly)any size

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How-to: Metal cannonballs of (nearly)any size

Unread postAuthor: Fnord » Tue Apr 03, 2007 9:48 am

A couple days ago I decided to try making custom lead cannonballs for my contest entry (don't know if it will be powerful enough to shoot them effectively though). After some trial and error, I got the process down to a reliable set of steps and decided to write a How-to for SpudFiles.
Here's how to make a semi-reusable mold to cast cannonballs of almost any size and any metal, with mostly common stuff from around the house.
This is basically an idiot's guide, meaning it is quite long and detailed, but if you want to make your own super accurate and cool looking ammo, this is worth reading.

[Note to Schmanman: I demand that you make one of these for the SWAT gun :)
I'd send you one but lead is expensive to ship]



Here's what you need:

I shouldn't even need to tell you that gloves/glasses are important when working with molten metal.

1. Wax (any kind will do, as long as it isn't too hard and brittle)
2. A can to melt the wax in
3. Plaster of Paris
4. A Bowl to mix the plaster in
5. A piece of the pipe you want to make ammo for
6. Cardboard
7. Aluminum foil and rubber bands
8. Ducttape
9. Pam (any nonstick spay should work)
10. A knife, file, hacksaw, and pliers or channel locks
11. Charcoal/A gas grill, or really anything you can get to high enough temp to melt your metal.
12. A container to melt metal in (steel soup cans will work for lead, zinc and aluminum)



Here's what to do:

1. Take the foil and put it over one end of the pipe, and wrap rubber bands around it until it is sealed tight enough to cast wax in.

2. Spray the inside of the pipe down with Pam; this will make it easier to remove the wax.

3. Melt the wax in your can by putting the can in boiling water, and pour it into the pipe.
You will want the wax slug to be a little longer than the pipe is in diameter.

4. cut the wax into a rough sphere, make sure not to cut middle down any, as it will become a smaller diameter than your pipe. Soften the wax in warm water if necessary.

5. Take your rough sphere and roll it around on the end of your pipe. Allow the edge of the pipe to slowly shave off bits of wax until it wants to fall into the pipe. This may take some practice, but if you do it right you should end up with a nice, nearly perfect sphere. save your wax shavings, as you might need to use them later

6. make a cylinder of wax about 1/4 the diameter of your ball (no bigger than half an inch), and 1-2 inches long it doesn't have to look good, it will only be used to make a channel for the metal to be poured into.
Attach this cylinder to the ball by heating one end with a lighter until it drips, and then just stick it on and hold it in place while it cools.


7. Find a box, or get some cardboard and make it into a box at least a quarter inch bigger in all directions than your ball and cylinder (I found that a 4-stick butter box works good for a projectile 2 inches or less.)

8. Mix up plaster until it is about the consistency of pudding and fill the box a little less than half full.
Then spray the ball down with pam and lay it down into the plaster until it is EXACTLY half buried.

9. Now you need to make grooves in the wet plaster with your finger(see the pictures below), this will help the halves line up when you are ready to cast metal.
Let the plaster harden.

------------------------
------------------------

Now comes the point where you have to pour the other half of the mold. I've had problems in the past with the two halves sticking and cracking when they are taken apart, but have found a way to avoid this entirely. If you want you can skip the next few steps and go to 10, but I always do this to ensure I don't break the mold.

A. Take the plaster out of the box. rip it if you have to.

B. Get a frying pan or something fairly shallow and fill it with hot water. The water should too hot to touch, but not boiling.

C. Take thin pieces of wax (did you save your shavings?) and put them in the water. If you shine a light into the bowl you will be able to tell the wax is melting and forming a liquid film on the water. (picture shown below)

D. Make sure your wax ball still has pam on it. There should be NO pam on the plaster you poured.

E. Dip the ball-side of the mold into the hot water(its best to use kind of a rolling motion)

The side you dipped should have a paper thin coating of wax on it. The thin membrane of wax will peel off of the ball because it still has pam on it (this is a good thing)

F. tape cardboard to the sides of the mold to form a box to pour the other half of the plaster in. Spray the inside down again with pam and go to step 10.

-----------------------
-----------------------


10. mix the other half of the plaster the same as the first batch and pour it in, making sure that it is worked in to every small detail of the mold.

Let it harden overnight


11. You should now be able to separate the two halves relatively easily. If you have done everything right you might be able to remove the ball without damaging it so it can be reused.
DON'T PANIC if your mold has little air bubbles in it. You can always fill them in before you bake it.


12. With the wax out, put it in the oven and bake it at 325 or so for at least a 45 mins.


13. tape the two halves together with layers of duct tape. they should line up nicely.
Put the mold in a pan so you wont waste lead if your mold leaks.


14. Now you are ready to cast the metal (lead, in this case).
Do this OUTSIDE; none of the gasses that come from molten lead are good for you. Wear a respirator/gasmask if you have one.


There is a good tutorial on casting lead at http://www.spudfiles.com/forums/viewtopic.php?t=6613& , which uses a portable gas stove to melt lead. I did mine on the grill.

Heat the lead up in the soup can and use your pliers/ tongs to pour it in(Are you wearing your gloves and safety glasses???)



!!!!!!IF IT STARTS BUBBLING VIOLENTLY IN THE MOLD, STOP POURING AND LEAVE THE AREA!!!!!!!

Bubbling usually means you have moisture left in the mold, which can sometimes result in an explosion. Wait until it cools down, remove the lead, and bake it again.


But if all goes well, fill it to the top and let it solidify (this took 20 mins for my 2" ball)


15. After the mold is fairly cool remove the tape and open it gently. Unless you waited a really long time, it will still be hot but you can pick it up with tongs/heat-resistant gloves and dunk it in water.


Now just cut off the extra lead with your saw and file, and smooth out any rough spots (Keep track of where your lead dust is falling, it's really bad for the environment)



TIPS:
--Your mold will probably last longer than one casting before it cracks beyond use (for lead anyways). Put it in a pan to contain the metal should it break
--while your pouring. Mine lasted 5 castings before I broke it by accident.

--Tire weights are a good source of lead. My tire place was nice enough to give me 20 pounds of them for free after I used the "I've got a Science Project..." line.

--If, for some reason you want to make a copper projectile, you're going to need somethin better than a soup can. Steel melts at a high temp than copper but I have never been able to keep a can together long enough to melt a usable amount of copper. Molten salt will also eat though cans quickly.

I probably should have said this earlier, but I thought it would be common sense:
DON'T SPILL MOLTEN LEAD IN YOUR GRILL!!!
Lead + hamburger = brain damage.
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Attachments
100_3613.jpg
The finished product. mine ended up being about a mm smaller than my barrel.
100_3613.jpg (31.33 KiB) Viewed 5500 times
100_3609.jpg
step 15.
If everything works right youll end up with something like this. you need to cut off the excess metal
100_3597.jpg
Yeah, thats how I melted my lead. I dont really recommend this though.
100_3608.jpg
step 11, after the mold separated.
100_3608.jpg (20.13 KiB) Viewed 5500 times
100_3607.jpg
step 10
100_3607.jpg (17.26 KiB) Viewed 5500 times
100_3605.jpg
step 9-C
When a good layer of wax has formed on the surface, you can see globules in the bowl by shining a flashlight in.
100_3605.jpg (22.13 KiB) Viewed 5500 times
100_3602.jpg
one half of the mold after it dries
100_3602.jpg (14.72 KiB) Viewed 5500 times
100_3587.jpg
what you should end up with after you shape the wax in the pipe.
100_3587.jpg (16.86 KiB) Viewed 5500 times
100_3588.jpg
step 5. shave the wax off by rolling it on the end of the pipe.
100_3588.jpg (12.47 KiB) Viewed 5500 times
100_3599.jpg
picture of step 4.
this is the rough sphere I cut.
100_3599.jpg (13.66 KiB) Viewed 5500 times
Last edited by Fnord on Thu Oct 07, 2010 3:54 pm, edited 1 time in total.
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Unread postAuthor: Fnord » Tue Apr 03, 2007 9:50 am

sorry, a couple of the images got switched around when I uploaded.
If You see any other errors pm me and Ill fix them
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Unread postAuthor: pat123 » Tue Apr 03, 2007 9:54 am

thats awesome i might try it but lead is toxic though :cry:
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Unread postAuthor: chaos » Tue Apr 03, 2007 10:04 am

lead is also i great damage utility lol :lol:

its always good when you want to totally wreck somthing :wink:
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Unread postAuthor: LGM » Tue Apr 03, 2007 10:07 am

If you want a non-toxic alternative to this you can use pewter, but it's really expensive. ($10.00 a lb)
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Unread postAuthor: chaos » Tue Apr 03, 2007 10:32 am

whoah $10 per lb?? man i think ill take the lead poisoning lol :lol:
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Unread postAuthor: A-98 » Tue Apr 03, 2007 10:49 am

ok, this is officially my favorite how-to ever. thank you, ive always wanted to figure out a way to easily do this.the lost wax method occured to me, but i could have done it like you.
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Unread postAuthor: SpudBlaster15 » Tue Apr 03, 2007 10:56 am

Don't forget that metal castings contract as they cool off, meaning that you must make the mold slightly oversize if you want the finished product to be of a certain size.

Remember, lead is highly toxic in even small quantities, and handling it can transfer toxic amounts to your skin, which can be ingested, or transfered to other surfaces of your home, etc. Be careful.

I have never used lead ammo, but from what I have heard, it deforms far too easily upon impact to be terribly useful. I have access to brass casting equipment, and I plan to make some ammo using this much harder, yet still dense material.
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Unread postAuthor: joannaardway » Tue Apr 03, 2007 1:00 pm

The verdict:
Pretty damned sweet idea.

I might well try that if I ever run short on steel ball bearings that fit well in my cannons. I have quite a lot though.

It could just be fun to fire a giant wax ball as well, so I might end up firing that too once I've made enough moulds.

Now I just need something that will contain molten tungsten...
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Unread postAuthor: A-98 » Tue Apr 03, 2007 1:04 pm

SpudBlaster15 wrote:Remember, lead is highly toxic in even small quantities, and handling it can transfer toxic amounts to your skin, which can be ingested, or transfered to other surfaces of your home, etc. Be careful.


hypthetical question, how many years earlier will i die if i were to have chewed on solder whe i was in 1st grade?...please tell me it will improve my lifespan :D
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Unread postAuthor: willarddaniels » Tue Apr 03, 2007 1:18 pm

Nice tutorial, well thought out.

Note on the water and molten lead subject: You bring up a very good point. When I was making the other how-to you referred to, I accidently allowed about 1 tbls of water to drop onto the boiling lead bath and the result was molten lead flying through the air in all directions. The water had penetrated the surface of the bath just enough to blast the a bit of the mix everywhere as a result of the very rapid evaporation and expansion. Luckily neither my equipment nor I suffered any damage, although it it did get all over my clothes.
Also, as SB15 mentioned and Fnord referred to, this stuff shrinks just a tad when it cools. This is nice for removing it from the moulds, but will affect performance.
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Unread postAuthor: A-98 » Tue Apr 03, 2007 1:26 pm

im rather confused around the water-wax part. is he using the heated water to melt the wax, which is floating on top? i found that you dont need that, however it is wise to have a double-boiler of some sort. i used to have a candle business around x-mas time. i had a rather ghetto double boiler, which consisted of a pot filled about 1/3 full of water, and some sourt of metal teapot (actually a candle making tool) which was filled with wax blocks and out in the boling water. this setup was inexpensive, yet prevented the wax from burning.
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Unread postAuthor: willarddaniels » Tue Apr 03, 2007 1:35 pm

^^^^^ I believe he used the water to melt the wax remnants only. He then dipped the first half of his mould into the wax before he makes the second half. This is to ensure he can separate the two halves when he makes the second half: so that there is a thin layer of something between the two halves and they break apart easily after the plaster has cured. Otherwise, it would not be re-usable and the wax would still be inside.
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Unread postAuthor: A-98 » Tue Apr 03, 2007 1:56 pm

ah, that makes sence. however, i would have used a sheet of wak papter that has the proper holes cut in it. there would be less imprefections due to lumps in the wax. also, it will make your mold look prettier. you could then open it up after the plaster has cured, and pull off the wax paper, then clamp your mold back together
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Unread postAuthor: Fnord » Tue Apr 03, 2007 2:44 pm

I tried wax paper, cling wrap, you name it, but Ive found that the process I described worked the best for me. stuff like wax paper didnt comform to the mold very well, so I ended up with gaps and airspace.

Edit: also, adding a layer of wax paper on top of the plaster before it dries can work, but it will seal in moisture and keep the plaster from drying.

**Note about metal contraction: This does have some effect on the final product, but not much. the reason my cannonball was slightly smaller is that I shaved off a little too much when I rounded it with the pipe.
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