Hardening and heat treating US Mint dies – 1878
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8 posts in this topic

The following excerpt is from a letter of Feb. 12, 1878 from Engraver William Barber concerning defective Trade dollar dies and hardening conditions at Philadelphia. (SF hardened their own dies.) A member asked abut this several months ago -- OK, so I'm slow....

[Page 2]

…I think that the risk of breaking dies in hardening or using, always a considerable risk, has been greatly increased by the process which they (in San Francisco) have used, of making the bottom of the die as hard as the face…and I greatly prefer our plan of exposing only about three parts of the steel to the sudden chilling and consequent contraction.

[Page 3]

   I would remark, we never shall get rid of this trouble of breakage, we can only reduce it to its minimum amount….I would like here to express my views on the means of reducing the breakage of the dies to the lowest point….

[Page 5]

   …I think we are under a great disadvantage in having to perform so nice an operation as hardening, in such a very limited space as our hardening shop affords. I know we ought to be alone while hardening, as the degree of heat befre cooling and the delicate shade of color afterwards, which indicates the temper, and changed from one tint to another so rapidly that we have to seize the very moment of required shade, and

[Page 6]

fix it by instant immersion, or it deepens into another color, and your opportunity is gone. I submit therefore that such an operation requiring absorbing attention, labors under great disadvantages in having to be performed in a confined room used for other purposes, and perhaps containing 4, 5, or 6 men in it working at other business, at the time we want the closest observation and attention….

[RG104 E-1 Box 110]

Edited by RWB
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you can tell that space was set up by someone who never had to do that job. No wonder they were having troubles with hardening the dies. The guy doing the job was blamed for the poor performance when the paper pushers would not provide what he needed, a little more space and a little peace, and the proper lighting.

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They had a 40-year old building that was obsolete the day it opened.

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It's interesting San Francisco decided to harden the entire die, I would think that they would realize that having some soft steel at the base would allow for the die to compress a little bit and not be as susceptible to cracking. Does the entry have any reasoning for why San Fran decided to do so? Philadelphia seems to get my view and seems to be just as confused as I am!

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This speaks to the skill of the early mint employees. Today the dies would go in a controlled heat treat oven until the exact optimal temperature. These guys had to have skill and tell from the color of the steel when it reached hardening temperature. Too hot and it’s brittle. Too cool and it isn’t properly hardened. All by the color of the steel. They had skills for sure. 

Edited by Woods020
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@RWBwe see this and many other examples where mints varied in processes. Dies are a prime example. The die prep was very different between Philly, New Orleans and San Fran. Why was there not an enforced SOP and why was there reluctance to share best practices? I know times were different but why wouldn’t they all figure out the “best” way and everyone follow that? Was it lack of communication, ignorance, ego?

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On 3/14/2022 at 6:15 PM, Woods020 said:

@RWBwe see this and many other examples where mints varied in processes. Dies are a prime example. The die prep was very different between Philly, New Orleans and San Fran. Why was there not an enforced SOP and why was there reluctance to share best practices? I know times were different but why wouldn’t they all figure out the “best” way and everyone follow that? Was it lack of communication, ignorance, ego?

I think it was a lot of on the job training of people who got their jobs initially via patronage. 

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Posted (edited)

Charles Barber tried multiple times to standardize everything relating to dies, but didn't get much cooperation until after New Orleans closed. The basic problem was that many of the presses were more or less custom built, which meant limited interchangeability of parts and little standardization. If a die stake cracked, a new one had to be made in the Mint's machine shop or by the company that made the press (Morgan & Orr, for example). There was no overall repair and replacement plan, so each mint managed equipment independently. The only time there was a common coin press was from 1837 to about 1845 when all the presses were built on Franklin Peale's plan and scaled according to his design drawings. When San Francisco opened a new problem was created: security. Dies were shipped west unhardened because SF wanted to cut their length to fit their presses, and HQ wanted to be sure that if dies were lost or stolen, they were very unlikely to be usable as soft steel. Die hardening was tricky business and very few were expert enough to handle coinage dies without ruining them.

Edited by RWB
corrected spelling
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