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 Replies: 142 / Views: 22,479 |
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Pillar of the Community
 United States
3330 Posts |
Quote:
I think we need to search for an example still in mint packaging. Great idea! I hope someone finds one! As you know, after many hours of research, I have found very little about Mint Testing. I have found enough data to make a circumstantial argument that they do...or must, however! Very frustrating!  I appreciate your recognition! Thank you!  You know, I have been a student all my life...I cannot stop studying and learning! I love a challenge like this! I will soon turn 75 and the areas I have studied have been many and varied. Someday I may actually sit down and attempt to list all the areas of my study! Of course my memory has gotten so patchy and feeble, I probably will not remember them all!  Thanks again! Edited by Pete2226
08/20/2015 7:06 pm
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Pillar of the Community
United States
3330 Posts |
I am thinking that it would be interesting to explain some of the details behind my thinking concerning the need for hardness testing of Copper Plated Zinc Planchets. There are four major zinc Alloys. I am listing them here along with their hardness and composition.
ALLOY 190
COMPOSITION (% by Weight)
Lead.............................0.005 max
Iron..............................0.010 max
Cadmium.....................0.005 max
Copper........................0.7 to 0.9
Zinc.............................Balance
Hardness (Rockwell 15T) 59 to 69
ALLOY 500
COMPOSITION (% by Weight)
Lead............................0.003 max
Iron.............................0.003 max
Cadmium....................0.003 max
Aluminum..................0.002 max
Copper......................0.003 max
Titanium...................0.001 to 0.004
Zinc............................Balance
Hardness (Rockwell 15T) 20 to 45
ALLOY 710
COMPOSITION (% by Weight)
Lead............................0.003 max
Iron..............................0.002 max
Cadmium......................0.003 max
Copper..........................0.10 to 0.25
Titanium.....................0.06 to 0.10
Zinc.............................Balance
Hardness (Rockwell 15T) 50 to 68
ALLOY 750
COMPOSITION (% by Weight)
Lead............................0.010 max
Iron............................0.010 max
Cadmium......................0.005 max
Copper.........................0.50 to 0.70
Titanium....................0.12 to 0.18
Zinc............................Balance
Hardness (Rockwell 15T) 58 to 72
A Hardness of 62 to 72 (Rockwell 15T) is the requirement of the U S Mint for Copper Plated Zinc Planchets. I think it is reasonable to expect that the Mint would require Certification for its planchets' Hardness and other specifications from its supplier and/or perform those tests itself. Variations in Alloy Composition can make a large difference in Hardness and consequently in the quality of the finished product.
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Rest in Peace
United States
7075 Posts |
Do you know what company supplies thr planche4ts to the mint? It may be possible to get them to send you a pic with an example -- ya know, so that us hobbiest can finally know what we are or are not seeing. Not asking for trade secrets -- just a little pic......It would be a nice public relations gesture....maybe.
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Moderator
 United States
23522 Posts |
As far as I know, a Zlincoln is pure zinc, not an alloy. Why would you need to test a pure metal for hardness? Annealing?
I'm not arguing the existence of hardness testing, but I've seen a few bb strikes in this thread.
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Pillar of the Community
Canada
2519 Posts |
Zinc cent planchets aren't annealed according to this Coinworld article. "Copper-plated zinc planchets are not annealed and they do not experience work- hardening." |
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Pillar of the Community
United States
3330 Posts |
Quote:
Do you know what company supplies thr planche4ts to the mint? Jarden Zinc is the supplier. http://www.jardenzinc.com/They have several brochures on the web site available for download. There are photos of blank planchets (see the last link below). Quote:
As far as I know, a Zlincoln is pure zinc, not an alloy. Pure zinc would be way too soft for the minting process. The U S Mint requires their Copper Plated Zinc Planchets to be of a Hardness of 62 to 72 Rockwell 15T. Pure Zinc will not meet this requirement.This information can be found on page 42, Section 2.4.1.1 of the Alternative Metals Study, Final Report, August 31, 2012 by Concurrent Technologies Corporation. Click on the relevent link at this page: http://www.usmint.gov/about_the_min...alreport2012 Quote:
Zinc cent planchets aren't annealed Correct! This is one of the benefits of using zinc. See Page 6 of (along with some photos): The Brochure Title is "Coinage". http://jardenzinc.com/techdata/JardenCoinage.pdfIf anyone is interested in additional details, the items I mentioned above and much additional information are things I have discussed in my posts earlier in this thread. Quote:
but I've seen a few bb strikes in this thread. I suspect that a BB Strike would produce at least a bit of a raised area on the opposite side of the coin. (?) Edited by Pete2226
08/22/2015 11:06 am
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Pillar of the Community
United States
3330 Posts |
I found the Coinage Brochure Link and corrected the preceding post to include it! Sorry!
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Pillar of the Community
United States
3330 Posts |
I finally found documentation for which Zinc Alloy the Mint uses! It is hidden away in the 400 page Alternative Metals Study report I referenced above and provided a link. It is found on Page 1, Section 1.1 Here is the quote: Quote:
Leading up to the alloy change made in the one-cent coin in 1982, copper prices were high enough that the intrinsic value of copper in a one-cent coin exceeded its face value of 1.0 cents. In response, the United States Mint developed and began to produce one-cent coins with a zinc alloy core (Zn alloy A190; composition Zn-0.8%Cu) that was electroplated with a nominal 8 microns of copper. The complete Composition of Alloy 190 is shown in my previous post. |
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Moderator
United States
23522 Posts |
Excellent detectice work, Pete.  This shifts me into purely learning mode.  |
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Pillar of the Community
United States
3330 Posts |
Thank you, SsuperDdave! Every once in a while, an Old Blind Hog finds an acorn!  |
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Moderator
United States
23522 Posts |
Young hogs find more truffles, but old hogs find the tastiest ones. |
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Pillar of the Community
United States
3330 Posts |
Quote:
Young hogs find more truffles, but old hogs find the tastiest ones. YUM! Your help in my research efforts - as well as all others' who have posted in this thread - is deeply appreciated! Every question, statement and doubt spurs me on to find answers. They help frame the questions in my mind.  |
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Pillar of the Community
United States
3330 Posts |
I have some new information! I contacted the U S Mint with this question: Quote:
I am doing some research and I am wondering if both the Denver and Philadelphia Mints perform quality control Rockwell Hardness Testing on a random selection of the Copper-Plated Zinc Planchets received in a shipment before proceeding to minting? Here is the response I received: Quote:
The United States Mint facilities in Philadelphia and Denver both perform incoming inspections for all raw materials received. We perform Rockwell hardness testing for quality control purposes prior to minting. It took them 10 days to answer! I did not expect an answer, but I am delighted to have one! Edited by Pete2226
08/24/2015 2:26 pm
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Pillar of the Community
United States
3463 Posts |
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Valued Member
United States
108 Posts |
An offshoot of the Ball canning jar company? Had a zinc plant for the lids. Weird what happens, huh?
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Replies: 142 / Views: 22,479 |
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Posted 08/21/2015 08:27 am
