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Die life, circulation coins 1975

RogerBRogerB Posts: 8,852 ✭✭✭✭✭
edited June 24, 2017 7:21PM in U.S. Coin Forum

A while ago someone asked about die life for modern coins. I came across this covering Jan-Oct 1975 (RG104 entry 330 [NN3-104-00-001], box 26, “New Dollar Coin Production.”)

Columns are: denomination, die life (strikes), planchet thickness, planchet diameter, coining force in kilopounds per square inch (ksi).

10c 465,000 0.0415-in 0.695-in 214 ksi
25c 230,000 0.0535-in 0.960-in 262 ksi
50c 370,000 0.0685-in 1.198-in 218 ksi
$1 230,000 0.0890-in 1.494-in 161 ksi

NOTE: To find tons per square inch divide kpi by 2.24. Kpi is also known as “kip/square inch.” If you are doing this in pascals, then there are 1.45037738007E-7 ksi in one pascal. The strike force for the dime is therefore: 1,475,478,057.92 pascals. 1 ksi = 6.8947572932 megapascals.

Comments

  • ManorcourtmanManorcourtman Posts: 7,891 ✭✭✭✭

    Interesting, thanks for posting. A while back I asked for opinions on 2017 Lincoln cent die lives. I was trying to determine the number of possible errors that could be created before a die was retired.

  • Peace_dollar88Peace_dollar88 Posts: 1,220 ✭✭✭✭✭

    Interesting. I would like to see what the first coin struck looks like in comparison to the last coin struck on a given die run.

  • rickoricko Posts: 98,724 ✭✭✭✭✭

    I find it interesting that the quarters seem to have a shorter span than the halves.... and the dimes the longest.... Not sure what significance that has, but there is likely a good reason. Cheers, RickO

  • silverpopsilverpop Posts: 6,591 ✭✭✭✭✭
  • WoodenJeffersonWoodenJefferson Posts: 6,491 ✭✭✭✭

    It would only seem natural that the ksi (kilopounds per square inch) would increase as the diameter increases, not so according to this chart. Physics is a conundrum.

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  • RogerBRogerB Posts: 8,852 ✭✭✭✭✭

    Mint engravers and coiners were constantly looking for ways to improve the number of strikes from a die. The clearest examples are 1913-16 Buffalos, 1916-20 dimes, 1878-1884 Morgans, plus all modern coins. Technology improvements combined with modeling and simulation software to help the Mint optimize the power curve in coin production. The pressure of Bicentennial dollars of 161 ksi, or 67 tons per sq inch, is awfully low and likely a function of the gentle, low relief design and limited detail.

    This is also a reminder that we don't know much about the technical insides of US Mint work -- the why and how of making coins. As in earlier eras, this information is not in our archives.

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