Graphite crucible ?

Discussion in 'Foundry tools and flasks' started by Bruce R., Apr 15, 2019.

  1. Bruce R.

    Bruce R. Copper

    There’s a plant not far from me that ships in scrap graphite, grinds it up to make pellets for some reason. Alot of the stuff is cylindrical and since I know the owners I carted a few, (10) pieces home ranging in size from 3” dia up to 8”. I was thinking I could hollow them out in my lathe to use as crucibles, I believe the stuff is pure graphite, any opinions ?
  2. PatJ

    PatJ Silver Banner Member

    Graphite is pretty fragile.
    Not sure if I would want to be near a big piece on a lathe if it came out, and it would be very difficult to grip and stay gripped.

    You could use the trick I use with wood patterns in the lathe, where I mount router where the cutting bit goes, and turn the wood pattern by hand while the router is running.
    This prevents the bit from grabbing and shattering the wood.

    I think I would just by a Morgan clay graphite crucible though.
    The dust would be very bad.

  3. Jason

    Jason Silver Banner Member

    lol... Sounds like nuclear fuel pellets. You sure it's graphite?

    The best use for your graphite haul is actually to make tools for the glass weenies. They are way overpriced and anyone that screws with glass needs them. Start with a ball mill and a block. The old biddies making beads will beat a path to your door. You can mail me my cut later. :p:D
    I'm serious... Look at the stupid prices for this stuff on here. A man makes these at a fair price and you'll turn the industry on it's head. Sell on etsy and fleabay.
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    There are many different grades of graphite and forming processes. Some things said to be graphite are not. Carbon gouging rods for example. If it is pure graphite, here's my take.
    • You see graphite crucibles all the time in the small jewelers melters. They are usually a few ounces but some are 4-5kg.
    • Graphite has excellent resistance to molten aluminum (and probably most metals) contact. It is commonly used for contact tools like degassing lances and stirring rods.
    • As already stated, it will be fragile compared to a commercial clay graphite crucible, namely very low impact strength which is not a very desirable quality for a crucible, though commercial crucibles aren't exactly stellar in this regard either. You might tap on a few of your pieces and see if they chip easily.
    • If strength was not an issue, it would likely be very thermally conductive and that is a very desirable quality for a crucible.
    • 8"D by 10"L is a very large hunk of graphite and large enough to make an A20 crucible.
    • As already mentioned, it would be very difficult to grip reliably in a lathe and may not stand up to jaw pressure well. If a piece like that got loose....
    • You would need to machine some shape on the outside as well so you could grip it with a shank.
    • I would never machine that much graphite in my shop. The stuff get's everywhere. The dust is electrically conductive and will short circuit boards and motors so consider that if you value any electronics or open armature brush motors in your shop.
    High quality commercial crucibles from A10-A20 size can be had for $80-$140 all day. Is it worth it to you?

    joe yard likes this.
  5. Bruce R.

    Bruce R. Copper

    I have an electric furnace or autoclave, or whatever you call it, and I was thinking of making small crucibles to melt silver coins to cast something useless out of, maybe a belt buckle or something, I thought the graphite would be good for that. Machining it is not a problem for me.
  6. Jammer

    Jammer Moderator Staff Member Banner Member

    I did something like that a few years ago. I had some bottom tapping ladle plugs that were probably a clay graphite. I used the "diamond "hole saws from harbor fright to bore out the center. It worked pretty well and I melted aluminum and brass in it, the when someone said it would never hold up to Iron temps, I melted about 5 pounds of Iron in it. I still have it, it does have a small crack at the top.
    If the graphite you are talking about is in large cylinders, 12 to 20 inches in diameter and 8 feet long, they are probably electric arc furnace electrodes. I think they have some clay in them as well.
  7. Bruce R.

    Bruce R. Copper

    There’s all sorts of shapes there, some of it even has large external threads.

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