Can you tell a real Rockwell Test?

Discussion in 'Error Coins' started by Bobs Tavern Arm, Jun 19, 2019.

  1. Fred Weinberg

    Fred Weinberg Well-Known Member

    Although I only have Medal Hubs, I have quite
    a variety of U.S. Mint Dies, and other medal dies.

    I will have some broken defaced US dies at the ANA in
    Chicago in August, available for study, as well as
    Olympic Coin Dies, Defaced US Mint Dies, and Torched
    US Mint Dies. Stop by and say hi and see 'em.
     
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  3. MommaHenn

    MommaHenn Active Member

    @PeteApple and @FredWeinberg ... thank you both so very much for all of the information and the absolutely professional & wonderfully executed dialogue!
     
  4. R_rabbit

    R_rabbit Well-Known Member

    :)
    I agree!
    Very interesting read indeed!
    Thank you!
     
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  5. Pete Apple

    Pete Apple Well-Known Member

    Thanks. Let me say again-only one of us is a professional and not I! I am deeply honored to be a part of this conversation! The only advantage I have is age (80 in just over a year!). I also love research.
     
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  6. Pete Apple

    Pete Apple Well-Known Member

    I asked the Mint if there was a time in the past when a Rockwell Test was performed on the face of a die. Here is their answer:

    "No, there was not a time in the past when hardness testing was done on a die face. However, there may have been isolated instances of hardness testing on the face of the die for other purposes outside of normal production (for example, research and development, root-cause investigation, or equipment testing/acceptance)."
     
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  7. Fred Weinberg

    Fred Weinberg Well-Known Member

    So, can we agree that there are no coins with
    RT marks on them?

    And, given that they are done on Planchets, that
    65 to 85 tons of pressure would wipe out any marks
    from that RT?
     
  8. Pete Apple

    Pete Apple Well-Known Member

    That the pressure would wipe out a test mark may be intuitive but I have seen nothing to demonstrate such
     
  9. Fred Weinberg

    Fred Weinberg Well-Known Member

    Pete, I've seen the Rockwell Test done on a Silver
    Eagle planchet at the West Point Mint.

    The small indentation would disappear upon approx. 75+
    tons of pressure on on it - just as it would disappear on
    a copper or zinc cent planchet under 65 tons of pressure.
    That's a bit more than intuitive, imo.

    That we've seen nothing would seem to prove that, not the
    other way, imo.
     
  10. Pete Apple

    Pete Apple Well-Known Member

    Did you examine that planchet after it was struck?
     
  11. Fred Weinberg

    Fred Weinberg Well-Known Member

    No, and I didn't see it struck. It was destroyed,
    I was told, as all others are, after it's been examined.
    Could one or more, or a few RT planchets been struck?
    Yes, that's a possibility.

    I guess you're saying that my assertion
    that 65++ tons of pressure would 'hide'
    or 'cover' or whatever, that small indentation
    on the planchet isn't more than a guess or
    pure speculation.

    The recesses of any coin die are far far deeper
    than any RT mark on an unstuck planchet.

    65 tons of pressure (approx) is enough for the metal
    to move into the deep recesses of the die. Why
    wouldn't that kind of pressure on the same disc of metal
    obliterate a small diameter, light, indentation?

    I've seen the RT done, and I've seen coin dies and hubs
    made at the Philly Mint; NO, I haven't seen any RT planchets
    being struck at all - but I'll feel fine with my position.
     
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  12. TheFinn

    TheFinn Well-Known Member

    Rockwell tests are done on the side of the die, not the face.
     
  13. Pete Apple

    Pete Apple Well-Known Member

    I asked the Mint a question about the effects of striking pressure on Rockwell test Marks on a planchet.

    Their answer is a bit confusing, but I think their answer is:

    · Tested blanks are scrapped

    · The Mint has considered allowing the tested blanks to enter coining production, but has not because they could not be certain that the Test Marks would be obliterated.

    · Whether or not they would be obliterated would depend on the design of the coin, the location of the test and the orientation of the planchet in the press.

    Am I reading the answer correctly? (I am thinking the “risk outweighs the benefit” means that the risk of allowing the tested blank enter production – and have a test mark survive production – outweighs the benefit of scrapping the tested samples.)

    Here was my question:

    “I know that the Mint does Rockwell Testing on selected planchets and a think that such a planchet is discarded after testing.

    My question is: If somehow such a planchet were struck, would the strike obliterate the Rockwell Test Mark on the coin?

    Do you have the ability to actually perform such an experiment? If so, I would appreciate knowing the results!”



    Here is the answer:

    “The in-process hardness checks are considered destructive tests, so any blanks that are tested get scrapped. There has been exploration of recovering those blanks, but depending on the location of the indentation, the design of the coin, and the orientation at which the indented blank would enter the press, there’s no guarantee that the indent would strike out. Lastly, the hardness samples represent a miniscule amount compared to full production quantities, so the risk outweighs the benefit.”
     
  14. Mike Thornton

    Mike Thornton Learning something new everyday.

    I'm no mathematician but I think the formula might be:

    "(total mint production/tested examples)*AND (to the 4th power)".
     
  15. Mike Thornton

    Mike Thornton Learning something new everyday.

    Just throwing a thought out there. Wouldn't the RT'ing occur on the die material prior to production of the dies? Seem's like a total waste of time and cost to test a production die for hardness after the fact. Then again, we're talking about the government. Wasting money seems to be a priority.
     
  16. desertgem

    desertgem Senior Errer Collecktor

    Perhaps to eliminate the pressure effect from the master die as the working die was produced in that time period.
     
  17. Conder101

    Conder101 Numismatist

    I would think if you were rockwell testing a die blank, you would testit BEFORE the end of the blank was turned in the lathe to create the cone pressed against the hub. You would test near the edge of the blank and then the subsequent lathing would cut away the tested area. No trace of the test would remain on the blank when it was ready for hubbing. And then after hubbing even more of the edge of the die body is cut away
     
  18. Pete Apple

    Pete Apple Well-Known Member

    Conder101 makes valid points. Testing protocol, however, requires that the tests (more than one impression) not be made too close to the edge. Testing protocol states that the reading must be taken at least two indenter diameters from an edge. Perhaps that is enough so that the test indentions (there will be more than 1) would be lost to the lathe.

    Also, according to the Mint, testing was not normally (there are exceptions) done on the die face, but on the side of the die steel.
     
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