Average life of dies, Philadelphia 1909
RogerB
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This is a summary of the average life of working dies report for 1909 from the Philadelphia Mint. (Actually, it is a "means and range report" dated January 11, 1910.)
We have similar reports for scattered years from about 1865 to 1942 and then later, but there is no consistent record and no engineering data to show how changes in dies affected die life.
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Useful info there. It would be interesting to see how die life changed, say every ten years.
Great Data.
I looked at the mintages for that year, tossed out the reverse die numbers as they could have been used in a previous year or a subsequent year, and looked at the difference:
Denom. MIA Produced Mintage
1 511621 115579874 115068253
5 455117 12040880 11585763
10 77396 10317396 10240000
25 374901 9642901 9268000
50 188874 2557524 2368650
$2.50 2844 444604 441760
$5 22560 649620 627060
$10 32446 217235 184789
$20 1171 162386 161215
I also did a 1 sigma calculation (standard deviation) for a couple dies, using a set of 3 (high, average, low) and the calculation is off the charts in a very BAD way (common manufacturing goal is 6 sigma ). I did not include Matte proof as I did not know if they were included in the data set.
Since this does not show the number of presses (probably exists somewhere) and were some presses dedicated to a particular denomination or varied, I could not determine on average how many coins per day were "lost" to set up strikes versus failed quality, etc. As a function of DPMO (defects per million operations), there would be a bunch of people looking for new jobs, using modern standards.
It also shows, at least back then, that someone could crank out 1, 5, 1000 pieces surreptitiously, and it would not even make a wiggle in the MIA pieces. Crank out 50 Lincoln Obverse with Indian reverse, and it would not ripple the counts.
Thanks for posting. Good info. Where do you find this stuff?
Hmmmm.... I get,
Typical rate of defective pieces varied by denomination and mint, but at Philadelphia it was around 1% for DE in 1909. However, die life at San Francisco was approximately 10-times that at Philadelphia for double eagles.
What the variations and range show is that there was generally poor quality control of dies and die steel.
Legal tolerance also comes into play. For example the weight tolerance on double eagles was 0.096899%. There were also tight parameters for alloy, and diameter, plus general physical appearance. With these and other constraints DMAIC would probably work best if Six Sigma analysis were attempted back in 1909. The Philadelphia Mint would have been between 2 and 3 sigma.
PS: In the previous we also know that Philadelphia Mint was experimenting with Eagle collars - possibly depressing the acceptance rate.
I'd like to see what the die life was back in 1904 when they were still cranking out $1 coins!
Interesting data, Thanks Roger. @mustangmanbob ...Good calculations... were/are you a Quality Engineer by profession?
Cheers, RickO
Quarters , lowest number 148 for both obverse and reverse dies. There must have been a catastrophic failure, perhaps a significant clash or a broken die that fouled the other die.
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Here is a scan of some data from 1954 - note that the source documents were longer than 11" so it is a bit jumbled toward the right, but all the data is there. It gives die life and includes proofs, a commem, and some foreign as well.
I got this from PhillyJoe a number of years ago. Includes some other years and some other documents related to dies. Other documents include: Security Procedures related to Dies and a 1956 interim report on retired dies including pieces struck and why the die was retired.
Here is the 1954 report. I see it is an eye test, but there is lots of data there. If you single click on the image, it enlarges it - at least on my PC.
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Cameonut - Very interesting table. What remains of these reports is in NARA at Philadelphia.
The proof averages are about double those of the 1936-42 period.
Circulation averages seem to be 3 to 4 times those of pre-WW-II production. A meaningful indicator of improvement in steels and technology.
Morgan dollar dies averaged about 250,000 but with a wide range. That is, some dies failed after a few hundred/thousand strikes, but many lasted up to 400,000.
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One of the things to recall is that when it came to die hardening, they had NO objective technology. It would have been color of the heated metal only and that's subject to a wide range of interpretations.
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It was only in the late 1880s that US Mints began testing printed color swatches.
Experimentation and scientific examination were not part of anyone's job, so little was done except as incidental to normal work.
Sweet, thanks !!!
Then I wonder what was going on in the Denver and New Orleans mints with die lives. I do know that planchet quality deteriorated with mixing of alloys in the branch mints. It is why usually the woody cents came from Denver and San Francisco. Metallurgical variations with blanks could also affect die life.
May of the New Orleans Mint's problems came from obsolete and inefficient equipment that could not keep up with Mint HQ demands for coins. Planchet annealing, especially of dollars, was a persistent problem.
Difficulties occurred at other mints, also. Most were related to aging equipment and antiquated processes.
I've seen no metallurgical analysis of "woody cents" - if one exists with would be helpful to have the data. That might help determine the cause of surface discoloration. Objectively, this kind of this is more likely the result of the whitening step in planchet preparation, and not alloy which occurs very early in coinage operations.
A recent study of 1904-P Morgans shows 15 die pairs for business strikes, 2 for proofs. The Mint Report for FY 1904 (ending June 30, 1904) shows 32 dies prepared for that fiscal year. The last dollar sent to the assay commission was in April 1904, so it would seem that none were made in FY 1905. The study also showed that dies were used and retired in pairs. Assuming there aren't any 1904 die pairs with a mintage that was entirely melted, there would appear to have been 185,000 coins per die pair.
New Orleans was an entirely different matter. Dies were used in a more "promiscuous" manner, with some emission sequence charts being a bit of a mess. One shows relationships between dies used for 21 die pairs.
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