Question regarding Grease-Filled Dies

Discussion in 'Coin Chat' started by JeffC, Feb 19, 2020.

  1. JeffC

    JeffC Well-Known Member

    I've read so much about grease-filled dies and saw many examples here in CT. While researching online, all I get are mostly photos of the end products - like this one that I have. (I call it my 192 Berty E-Cent. LOL.)

    20200217_210434 copy.jpg

    But what I'm after is to understand why the grease within the recesses of the die doesn't just get displaced and then "splash out" under all the tons of pressure during the strike. When I think of grease-filled dies, I envision putting one ice cube tray over another one which is filled. Then the water in the lower tray would just get displaced. Why doesn't that happen to the grease in the die during the minting process?

    I've viewed numerous videos on the minting process, but none goes into that part in detail. Thanks for your help.
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  3. paddyman98

    paddyman98 Let me burst your bubble! Supporter

    The grease becomes compacted. It turns really hard inside the spaces of the Die. It's not liquid or viscous at that moment.
    furham, JeffC and RonSanderson like this.
  4. JeffC

    JeffC Well-Known Member

    Ok, thanks.
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  5. Collecting Nut

    Collecting Nut Borderline Hoarder

    It's not loose grease but more solid with all the other debris.
    Last edited: Feb 19, 2020
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  6. Kentucky

    Kentucky Supporter! Supporter

    Did you ever go water skiing...when you come off those skis, the water is HARD!!! Similarly when the die strikes down, the grease or oil resists being compressed and gets HARD!!!
    JeffC and Numiser like this.
  7. Kentucky

    Kentucky Supporter! Supporter

    Reminds me of a demo I saw once where a gallon jug is filled to the brim with water and a cork is inserted in the neck. A rap on the cork transmits to the jug (since the water can't be compressed) and the bottom breaks out.
  8. thomas mozzillo

    thomas mozzillo Well-Known Member

    Occasionally the impacted debris will come loose and fall out which can result in a "dropped letter" and show up on the next coin struck. NGC explains it better:
    JeffC likes this.
  9. CoinCorgi

    CoinCorgi Derp, derp, derp!

    Water is incompressable. Doug's head is filled with water. Doug's head is incompressable. Or is that incomprehensable?
    Randy Abercrombie, JeffC and Kentucky like this.
  10. JeffC

    JeffC Well-Known Member

    No, but come to think of it now, a friend of mine busted his eardrum when he fell off his water skis. I recall thinking it was odd that water could do that.
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  11. JeffC

    JeffC Well-Known Member

    Thank you for the link. Will check it out.
  12. JeffC

    JeffC Well-Known Member

    @thomas mozzillo, is a "dropped letter" (Photo 5 in your link) considered a mint error? Or, like a grease filled die, it's not.
  13. thomas mozzillo

    thomas mozzillo Well-Known Member

  14. JeffC

    JeffC Well-Known Member

  15. Johnny61824

    Johnny61824 New Member

  16. Conder101

    Conder101 Numismatist

    Why doesn't it "splash out? Think about this, as the die makes contact with the surface of the planchet and the field of the die starts forcing into it all the incuse device areas are now SEALED. Nothing in these devices areas can get out. As the die forces further intot he planchet the meter continues filling those device cavities. Gasses in the cavities can be compress and the metal eventually fills the void completely. But liquids (and we can consider the grease to be a liquid) are incompressible for all practical purposes so the grease stops the planchet metal, but can't "squirt" out because the planchet has sealed it in.
    paddyman98 likes this.
  17. JeffC

    JeffC Well-Known Member

    Thanks! I understand now. But still, how I wish I've got a few photos of the striking process to see and really appreciate it. Youtube and U.S. Mint videos don't go into the nitty gritty. Anyhow - thanks for the very thorough explanation.
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