Questions for the metal working crowd

[Shawn Pixley]

So I am working on lost wax casting. The current project is to make "signature emblems" for my furniture pieces. I plan to cast them in silicon bronze with a penny for the date. I picked up some ingots of silicon bronze. I would like to cut them down or granulate them for casting.

How would others cut these? I could use a hacksaw (sounds like a horrible experience if trying to do a a single time). I could use my WW bandsaw but I think i would wreck the tires). How about a 4-1/2" angle grinder? Other ideas?

Has anyone granulated bronze? If so, how did you approach it?

I picked up a vacuum investing set-up and a centrifugal casting apparatus. I have no container / shroud for the centrugal arm. Has anyone made an enclosure? If so, how did you do it?

[Dan Hintz]

If you don't wish to grind, what about a blowtorch to cut through them? Any slag would simply drop to the floor to be scraped up and put in the pot.

[Michael Hammers]

Just curious if you have seen any of the vieos by a fellow who goes by the handle Tubalcain.
He has several videos on foundry work that cover what your question is.

He is really entertaining and knowledgable. I have learned a lot just from viewing his videos.

He covers a lot of information for "newbies" like myself....from foundry to lathe set up and work.

HTH

M

[Shawn Pixley]

Thanks. I loked it over. He primarily does sand casting. Sand casting is more foregiving in calculating the metal needed as it is no big problem if you melt more than you need. The excess is just not poured. With centrifugal casting, if you have too much metal it is flung across the room. Being splashed with liquid metal at 1900F will ruin your day.

I need to reduce my ingots to a granulated or other finer form so I may measure it out at the gram level (31.1 grams pr troy ounce). I've done a lot of cuttlefish and sand casting in bronze and aluminum.

I saw a youtube where bronze or silver is granulated by pouring the liquid into a flower pot with a semi-circular bowl upside down. Both the flower pot and bowl were coated in powdered charcoal. The charcoal insulates and cushions the splatter coming off the bowl. I was hoping that someone had a better technique. I am not looking forward to cutting the ingot into ~1/8 of a CC pieces.

[Dan Hintz]

For the centrifugal caster, you could always place a small "bulb" at the mouth... any excess would bubble out of the top of the casting machine, but would be captured by the bulb. You wouldn't need to be so exact that way.

If you could get the metal to drip rather than pour, you could drop it from a distance of a few feet into some water. That would create small balls. Maybe pass the metal through a large-mesh sieve to get it to break up as it falls?

[Shawn Pixley]

For centrifugal casting, the molten metal is neither dripped or poured. It is flung through centrifugal force from the crucible which is mounted on the broken arm centrifuge with its exit against the flask. I watch a fellow student cast too much metal two weeks ago. He over calculated by maybe an ounce. Molten bronze was flung out after the flask was full. Luckily the shroud kept anyone from being hurt. I operate under an abundance of caution when working with 1900 degree F metal. I'm not like other people, pain hurts me...

[Dan Hintz]

Yeah, but don't you pour into the top of the center of the machine (or maybe it's just the ones I've seen). Big disc with multiple copies of the design around the periphery, with runners going to the center of the disc. Metal gets poured into the center and centripetal forces take care of the rest. If that center portion had a bulb on it, you could see when you've poured enough and the bulb will still hold the extra metal. That extra ounce your fellow student used would have been captured right on top of the disc rather than slung outwards.

[Shawn Pixley]

Dan,

You're think of the more industrial scale equipment. Below is a picture of a more typical unit.

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The metal is melted in the crucible while on the arn. The flask is heated in the kiln (after burn-out) and placed in the carriage. The crucible is slid along arm so that the "pour" hole aligns and is locked into the flask's button. The pin is released from the arm and both arms spin flinging the metal from the crucible into the flask. It spins for a couple minutes. The flask is removed a let sit for a couple minutes before quenching.

If there is more metal than the flask can hold, the molten metal leaks from the connection of the flask and crucible while the arm is spinning. This flings the molten metal in all directions. The home brew unit above uses a wash tub. It should have a lid on it as well. While I have never used a multiple cetrifugal casting machine, I suspect that metal measurement is important there for the same reasons. You can't have an "occlusive" seal between the crucible and the flask as there is no way for the air to escape without venting sprues. If you were able to seal it, it would also be important the not have too much metal. With too much metal in the flask the metal would harden between the crucible and all the flasks. You would need to saw off the sprues while on the machine and then burn out the flask.

['Jacques Malan']

The only time I had to reduce a big block of zinc into smaller pieces I used my woodworking bandsaw, and you are right, it wasn't a good idea.

Is it possible to smelt the entire ingot and recast it into a thin sheet? then you can snip of pieces as needed. Depends on how big the bronze is and how much you can cast at a time.

(I am quite sure there is technique to do this, but my mind is blank on it and I cannot think of the right terminology.)

[Charles Wiggins]

So I am working on lost wax casting. The current project is to make "signature emblems" for my furniture pieces. I plan to cast them in silicon bronze with a penny for the date. I picked up some ingots of silicon bronze. I would like to cut them down or granulate them for casting.

How would others cut these? I could use a hacksaw (sounds like a horrible experience if trying to do a a single time). I could use my WW bandsaw but I think i would wreck the tires). How about a 4-1/2" angle grinder? Other ideas?

Has anyone granulated bronze? If so, how did you approach it?

I picked up a vacuum investing set-up and a centrifugal casting apparatus. I have no container / shroud for the centrugal arm. Has anyone made an enclosure? If so, how did you do it?

Bronze is a relatively soft metal. You can cut it by any method you would cut aluminum, it may just take a bit longer. I would do the hacksaw with a course blade. It may take longer but you can cut a narrow kerf so you're not losing as much metal as you would with a grinder. I've never dealt with granulated metal, so I have no clue about that.

I don't have much experience casting on that small a scale. It was years ago and we vacuum cast.

[Leigh Betsch]

How about melting it and pour into smaller billets. Like filling up a ice tray..

[Charles McKinley]

Do you have access to a milling machine? Make perty shavings to weigh and melt down.:rolleyes:

Milling type bit in a die grinder?

Hit it with a plasma acr and have a way to catch the molten droplets as they spray off.:D My favorite option!

Chuck up the ingot in the lathe and turn off the weight of shavings you need. You should be able to get a really nice chip going if you get the feed right.