Die wear for gold coins opposed to wear on silver / copper-nickel

Aspie_Rocco

A recent gold slug thread with evidence of die wear/ fatigue/ deterioration reminds me of a lingering technical questions.

Setting 1800s- early 1900s
When gold was a circulated coin pre 1930s....

If gold is so soft as a metal, why do the dies break down and or wear out?

What is the life span of a die for gold? How many coins?

I saw somewhere approximately 200k to 225k nickels were made in past decades with the average die.

Are dies for gold prepared in the same fashion as for silver, copper, or copper-nickel?

https://forums.collectors.com/discussion/1011225/which-one-would-you-choose#latest

BillJones

I don’t have all of the answers for you, just some facts.

• In the early days of the U.S. mint, the quality of the steel that was used to make the dies varied greatly. There were also issues as whether the steel had imperfections in it, like gas bubbles or foreign material. All of these factors could limit the useful life of the die.

• For example, there two varieties of 1796 No Stars Quarter Eagles. It is believed that the first variety was struck in September and that only 66 pieces were struck then because the reverse die broke.

• The larger the coin, the greater amount of pressure it takes to strike it. This was true for all coins in all metals.

• So far as the slugs go, when the 1915-S Panama – Pacific $50 gold coins were made, one of the dies cracked early on and production was held up because they had to sink another one. The Pan-Pac $50 gold coins were stuck on medal presses, not coin presses. That shows that it took a lot of pressure strike those coins. Slugs are big coins. Even though gold is soft, it takes a lot pressure to strike a coin of that size.

• I don’t have any data on how long the gold coin dies lasted. In some cases the dies had be discarded not because they are unusable but because the year had changed. The mint didn’t always discard the previous years’ dies, but that certainly played a factor.

I hope you found this interesting. Answering you question would involve more study and assumptions.

CaptHenway

Excellent questions to consider.

I have no answers, but after thinking about the OP's questions I have one possible suggestion. Gold coins were the Mints' top of the line product. Full strikes would have been desirable as a matter of prestige, and as an anti-counterfeiting measure. High striking pressure yields good strikes and short die life. This may have been an acceptable trade-off.

BustDMs

Bills comment that it takes a greater amount of pressure to strike the larger coins is slightly misleading for a die deterioration study. While it did take more force from the screw press to strike the larger coins the stresses on the dies themselves was greater for the smaller coins.

Think of it this way. A woman in high heels will sink into the ground much quicker than the same person in flats. This is because the pressure is concentrated in a smaller area. Half dime dies suffered more stress related failures than the larger coins.

Hope this helps a little.

asheland

Interesting thread!

RogerB

Gold coin alloy is not "soft." The hardness of annealed planchets was similar to annealed silver. After striking a gold coin has a hard, but thin, exterior that reduces abrasion. Once this layer is broken, the exposed surface is somewhat softer and that leads to increased wear. (Documentation is in the British Royal Mint archives.) Further, the U.S. routinely recoined gold coins to help maintain pieces in circulation that met legal standards. There was a vast recoinage in the 1870s when light weight coins were redeemed and melted, then issued as new pieces.

The largest issues of gold coins were double eagles, and nearly all of these were exported and melted. Silver coins were made for domestic use and circulated here, but not in other countries to any extent. This situation produces a sampling bias that cannot be directly corrected. Thus, we see more effects of die wear/erosion on the coins we see, because we see a much greater proportion of coin produced.

In researching the Saint-Gaudens double eagle book, it was evident that the coins represented a skewed sample, and that on close examination, coins had the same types of defects seen on other coins of similar size, such as silver dollars and half dollars.

Aspie_Rocco

Thank you everyone for the replies and explanations. I love the information and food for thought it all provides.

davewesen

@BustDMs said:
Bills comment that it takes a greater amount of pressure to strike the larger coins is slightly misleading for a die deterioration study. While it did take more force from the screw press to strike the larger coins the stresses on the dies themselves was greater for the smaller coins.

Think of it this way. A woman in high heels will sink into the ground much quicker than the same person in flats. This is because the pressure is concentrated in a smaller area. Half dime dies suffered more stress related failures than the larger coins.

Hope this helps a little.

... But a 300 pound man wearing size 14 sneakers may sink into the ground more than a 120 pound lady in high heels .. depending on how hard the ground is.

BustDMs

Ok.......

Just making a point that PSI makes a difference.

But the 120 pound lady is actually standing on a rock and the guy is in quicksand

Oldhoopster

Did a quick check of metallurgical hardness measurements (emphasis on quick).

For annealed materials
Sterling Silver (92.5Ag) = 65-75 HV (Vickers hardness)
22K gold (91.7Au) = 70-75 HV

Generally, they look pretty close.

I couldn't find exact values for 90% alloys and I would expect the hardness values to depend on the alloying metal, so there could be variability over the years, particularly with gold. And, as others have pointed out, the striking pressures will have a significant affect as well.

Qualifyer: I'm not a metallurgist, but I think I know enough to make myself dangerous. Any corrections by people who do know metallurgy are more than welcome