1932-s Quarter RPM?

[billscoins]

Not to confuse matters, but there are other forms of design extra thickness that many associate with machine damage doubling and they are not.


In my studies of the anomalies called trails and wavy steps, I have also encountered another form of extra thickness (that I categorize as design extension) caused by movement of the die against the hub at the end of the hubbing process. At times, instead of just a high point on the hub, a leading edge of a design element on the hub will be drug across the die giving the appearance of extra thickness of that design element. One way to identify such extensions is the absence or continuation of flow lines (from the surrounding field) into the extra thickness. I have a 1997P Lincoln cent die that shows this type of extra thickness very well in the word LIBERTY, with some of the affect showing in IN GOD WE TRUST as well.

Just wanted to add to the information on this very informative post.

BJ Neff

I have experienced this kind of problem in my work place almost daily for about 35 years. I find them interesting and challenging. A common reason for accepting a problem as a mystery has been, either I was looking at the problem from to narrow a scope (leaving something out) or I was not seeing what was in front of me (my inspection equipment was inadequate). ALL MANUFACTURING PROCESSES must have their parameters defined and under control or it must be halted in order to regain control. Otherwise, scrap will pile-up faster than it can be disposed of. Someone at the mint knew what caused this and how to correct it. All metal working processes depend on machines with sliding clearances in the working parts. Always these clearances increase due to wear and must be brought back into tolerances in order to keep producing parts to specifications. Parts are checked in process and the machines are adjusted or the process is halted for repairs. So we should be able to identify the cause by examining the coins produced and evaluate the process just like they would have at the time of production. I’m not convinced we cannot recreate the thought process of the mint employees who make this coin.
Mr. Neff (BJ?), I welcome your input about the hub. It may be another trail, which I must take in this quest for knowledge. However, first the mystery of how MDD could have produced only the doubling of the mintmark must be solved. Either we can simulate it or it is not the cause.
This mystery seems to affect how coins are graded so I hope its solution will help clear up a gray area in this arena.
I thank everyone for their input and hope you will continue to express your thoughts.
Bill

[wavysteps]

Bill - Oddly enough, while searching through some change, I did throw back a 1980-D Lincoln cent with the exact same problem, machine damage doubling isolated on the mint mark, just a couple of days ago. Now I wish that I had saved it; it may have provided additional clues to what is happening.

I also remember sending James Wiles an isolated machine damage doubled mint mark (Lincoln cent), in hopes that it was a RPM, for I found it peculiar that this kind of damage could be isolated to that extent.

On the 1980-D that I just threw back in the pile; it was flat field doubling with continuous metal flow lines from the field into the doubling; definitely MDD.

Also "BJ" is fine.

BJ Neff

[billscoins]

Bill - Oddly enough, while searching through some change, I did throw back a 1980-D Lincoln cent with the exact same problem, machine damage doubling isolated on the mint mark, just a couple of days ago. Now I wish that I had saved it; it may have provided additional clues to what is happening.

I also remember sending James Wiles an isolated machine damage doubled mint mark (Lincoln cent), in hopes that it was a RPM, for I found it peculiar that this kind of damage could be isolated to that extent.

On the 1980-D that I just threw back in the pile; it was flat field doubling with continuous metal flow lines from the field into the doubling; definitely MDD.

Also "BJ" is fine.

BJ Neff

BJ, As I understand this process the metal of a blank's field flows into a cavity to form the mintmark. Then, if it is MDD it is sheared or pressed into the new shape ( the doubling) after or during the striking process. The flowlines of the metal from the field would not flow into the doubling would it? As I see this process, the material for the doubling must come from the letter already formed by the cavity (without the doubling) not the field of the coin for this to be MDD?
Bill

[billscoins]

1932-s rpm?

Question for James, Mike & BJ,
When a coin shows a pressed (pushed) or sheared (sliding) condition where the metal flows from the mintmark to the doubled area is that conclusive evidence of MDD? Alternately, if a coin shows flow lines into the doubled areas from the field, would that be conclusive evidence of a doubled die condition?
I believe these two conditions are mutually exclusive.
(That’s really 3 questions, isn’t it?)
Thanks for your help, Bill

[diamond]

Marginal shelving and/or shearing indicates that the die or the coin moved laterally after the hammer die reached the lowest point of its downstroke. Machine doubling can affect the face struck by the hammer die or the anvil die. Severe machine doubling almost always affects the face struck by the hammer die

A doubled die has a distinctly different appearance. There is no marginal shelving and there is no shear. Instead you have furrowed letters and numbers, split serifs, and a rounded look to the accessory elements. There are no "flow lines" as far as I'm aware. I'm not sure what "flow lines" are in this context.

[billscoins]

1932-s rpm?

I know you are aware of the following but to clarify my Questions: Metal which is cold worked or pressed into a cavity, flows (plastic deformation) and is work harden in varying degrees proportional to the forces applied. Under enough magnification the surface shows stretches or tares (small localized factures or stress cracks), which often indicate the direction of metal movement. I know that copper and silver are vary ductile metals so these “flow lines” may not show up normally to a low level of magnification.
I hope this clarifies my questions.
Bill

[diamond]

I understand what you're saying now. Under the levels of magnification that are usually employed in the hobby, these flow lines will not be visible. I figure you'd need an electron microscope to see them clearly.

[wavysteps]

When I look at the sheared machine damage, mostly what I see are scraped lines formed by the edge of the design element affected. However, with flat field doubling, the "flow lines" are from the die itself.

As I see it, with this type doubling (flat field), it is the coin bouncing back into the retreating die. The formed design element clashes with a portion of the field, transferring the "flow lines" (caused by die erosion) to that area (flat field) of the design. It may not be an exact continuation, however, the general direction of these "flow lines" will be constant with the surrounding field's "flow lines".

Of course, if you have a die without some sort of die erosion, these flow lines will not exist.

From the conversation, I think that we were talking about two different types of "flow lines", both of which do apply (sometimes occasionally) to this type of anomaly (MDD).

[Speedy]

Wow---I take a break for a few days and a book is written!!!

I have increased the magnification used to 30x with a loupe and have noticed what appears to be; 1. A piece of metal from the bottom serif is pushed up onto the top of the letter, & 2. Another piece pushed over from the top serif to the top of the letter.

Did you get to take any photos of what you were seeing there? If so I would really like to see them!

[billscoins]

Speedy, Please look at post #25 the 1st is your coin and the 3 others are mine. I think both coins came from the same die.???? The best picture I have of the serifs distortion is the 2nd one. When I look at the bottom one with a 30x look it looks like a piece has been push up onto the surface, which would indicate a sliding force has pushed it across the surface of the die and produced galling on the surface of the coin. A force that has held the coin down and pushed it sideways. This is clearly MACHINE DAMAGE, however, how could a downward force (strong enough to produce galling on the surface of the coin), start shearing half way up the letter and leave a sharp ledge (from a worn die with rounded edges)? The coin does move sideways relative to the die on my coin this is evidenced by the galling on the top surface. This means that machine damage is present on my coin; however, the evidence does not conclusively show that it formed the doubling in the coin.
A possibility may be a few coins were made with a doubled die. This may have made it harder for the coin to release from the die and could have produced increasing amounts of damage to the coins as the die wore.
I’m looking for pictures of the mintmarks used on the coins in 1932-s, this may tell us more of the situation, which created this doubling.
Thanks for your help,
Bill

[Speedy]

Thanks---I'll go back and check out those pic's....I must have missed them.
Give me awhile to think this over--and I'll try to post again