1994d DOUBLE DIE?

[diamond]

The design rim and the reeding are both produced by the strike. The freshly-punched out blank has no marginal elevation. However, it is then sent through the upset mill which produces a low proto-rim.

[wavysteps]

Mike - Curiosity has got me. Has there ever been a case reported where a blank (instead of the planchet) has been struck by the coin dies? Would the absence of the rim be a clue to this happening?

BJ Neff

[diamond]

There are plenty of such errors, especially in quarters. They are exceedingly rare, however, among copper-plated zinc cents. I've only seen three of those. They're really only detectable when a coin is broadstruck or struck off-center. In such coins there will be no proto-rim along the unstruck margin of the coin, and the edge will typically show the cut-and-tear texture that one associates with a blank.

I should note that many wrong planchet and off-metal errors are struck on blanks. That's because they're usually sent through the wrong upset mill as well, and the blanks are too small to be rolled and squeezed. They're simply propelled along by the planchets behind them.

[wavysteps]

Thanks Mike for the valued information. By the way, for all interested, I was able to view a 1939 Jefferson nickel, AU-50 condition, EDS with the famous DDR-001 last night at our coin club meeting. A vey nice coin indeed.

BJ Neff

[billscoins]

Thank You Mike & BJ,
Pleaseeee keep up the discussion. I need all the input I can get in order to understand the process the mint used.
In industry these parts would be produced on a press with a progressive /compound die combination with about 6 stations built into the die. The strip would be feed in the first station and then pushed thru the others being formed up progressively until the last where the part would be separated (from the web holding it & dropped thru the die) while the strip was chopped off and push out of the press. Each hit would make a part though the strip would feed from station to station with each hit of the press.
The process the mint used may have been about 40 years behind what industry was using. I can only guess at this point.
Bill

[billscoins]

Hi everyone, More thoughts……….
I have not seen the process used at the mints, however I have seen 100’s of processes in plants for the production of metal parts. One of the thoughts developing about this process from the coins I’m examining is that the traditional process has change since the definitions were proclaimed for double dies. I believe that these coins (1994 quarters) may have been formed on machines specially design for high-speed production. The normal designs for special machines are usually divided into 2 classes: rotary or transfer machines. Both types have multiple rams, which strike at the same time, So with each strike all rams hit many stations. This is different from the traditional single ram strike.
Industry typically will advance from a single ram machine with a progressive/compound die to a rotary machine and then on to a transfer machine to increase production volume. I’m beginning to believe these coins were produced using a rotary machine with many stations and many rams striking at the same time. The blanks are feed into a machine (either with or without rims and reeding ?), and each strike would produce a completed coin after each index of the central dies holder (or rotary table). The dies and the punches (in the multiple rams) would serve many functions and be of different configurations. Does this make sense?
Thanks, Bill

[diamond]

Each press is a stand-alone unit. While some cent, nickel, and dime presses used in the past employed two and sometimes four dies operating simultaneously, I believe quarter presses always used a single die pair. The high speed Schuler presses used nowadays use only a single die pair.

[billscoins]

Hi everyone, More thoughts……….
I’m reading Alan Herbert’s Mint Errors (7th Ed.) and a lot of the answers on how MDD occurs are appearing in his 400 categories of mint errors. I believe we can piece together what may have happened by examining the consequences of his 2 observations listed below:


1. On PG 109 Mr. Herbert states: “Even today every die, and every hub, that comes out of the Philadelphia Mint gets at least some minor recutting, as a skilled engraver takes the die as it comes from the hubbing press and ”touches up” those little details that may be missing from the hub.”
2. And on PG 20 he details the modern die making process where he states the previously struck coin “is pushed up out of the coining chamber by the anvil die”.

The areas of MDD are about 3 thousands of an inch (.003) wide and abount .0005 high. The lines of reeding opposite the doubling are about.003 deep, but are not continuous (some are filled in near the top at the doubling side).

A way I think this MDD may have occurred is as follows. The collar had build-up inside opposite the doubling that held the planchet up on one side. The coin rocked into position as the pressure build-up and the push doubling occurred as the coin settled into the spring-loaded anvil die. The reason for the localized effect was that the die had sharp edges around the profile, which were not polished with the required small radiuses on the relief in the problem areas. This caused the metal to shear not flow in these areas. These radiuses had to wear in or be touched up by an engraver in order for the MDD to disappear.
Does this make sense?
Thanks, Bill

[diamond]

Herbert is wrong about the retouching. Hubs and dies are not retouched. As far as I know, they've never been retouched except on very rare occasions.

[billscoins]

I mean no disrespect here, but………
I hope we can open a discussion of this phenomenon without relying on repeated misinformation that someone may have heard from the mint. I have worked on projects for our government where I had to say certain things & could not even say that I signed a confidentiality agreement for a 10-year period.
I’m beginning to understand the process the mint uses and I believe it is no different than the processes industry uses. I think the mint developed its processes using good machining practices and designs and ,as I am very familiar with these processes, think that everyone should review Mr. Herberts Mint Errors ( 7th Ed) Book Pages 160 to 164. These pages describe factual occurrences that happen during die try-out and set-up while bringing a die on line.
My point is that If a sharp edge (with no taper) on the die is not rounded ( or has to small a radius) , it will try to shear the metal during the hit not push it, as the hit causes the metal to flow into the cacity.
Thanks, Bill

[billscoins]

Also one more thing I've noticed about these parts, the finished coin dia. is about .003 smaller on the coins with MDD than the coins which do not have the doubling. My sampling size is only 4 coins with MDD (2 from P & 2 from D) and not doubled- (9 from P & 4 from D). The collar size was different on the dies with MDD. Not sure what how this affects the MDD?

Even if we disaggree on how things were done at the mint, I hope you will express your thoughts and set me straight.
Bill

[diamond]

Are your measurements taken in fractions of an inch or fractions of a millimeter? What did you use to take your measurements? Did you take them at several different points around the edge and averaged them? You would have to have a much larger sample and you would have to establish statistical significance before I would attach any importance to your findings. From the standpoint of etiology, slight variations in collar diameter shouldn't matter in the production of machine doubing.

[diamond]

I mean no disrespect here, but………
I hope we can open a discussion of this phenomenon without relying on repeated misinformation that someone may have heard from the mint.

I'm not sure what information you're referring to. My evidence comes primarily from the coins themselves. There is absolutely no evidence of retouching on coins apart from a few rare exceptions.

My point is that if a sharp edge (with no taper) on the die is not rounded ( or has too small a radius) , it will try to shear the metal during the hit not push it, as the hit causes the metal to flow into the cavity.

I don't understand your point. Machine doubling is variable in its expression. That's something the coins themselves reveal. Sometimes the design is pushed to the side and sometimes it is flattened from above (or below). And some show an intermediate condition. Machine doubling varies in severity in coins struck by the same dies, which is to be expected when a die is loose or the machine is vibrating.

[billscoins]

"Are your measurements taken in fractions of an inch or fractions of a millimeter? What did you use to take your measurements? Did you take them at several different points around the edge and averaged them? You would have to have a much larger sample and you would have to establish statistical significance before I would attach any importance to your findings. From the standpoint of etiology, slight variations in collar diameter shouldn't matter in the production of machine doubing."

I know the sampling size is to small, however, in the real world it shows that the clearances necessary for the part to move enough to form the doubling is present.
Measurements are in inches taken with a micrimeter and are an average from several readings around the O.D.
Thanks for your reply,
Bill

[billscoins]

I'm not sure what information you're referring to. My evidence comes primarily from the coins themselves. There is absolutely no evidence of retouching on coins apart from a few rare exceptions.



I don't understand your point. Machine doubling is variable in its expression. That's something the coins themselves reveal. Sometimes the design is pushed to the side and sometimes it is flattened from above (or below). And some show an intermediate condition. Machine doubling varies in severity in coins struck by the same dies, which is to be expected when a die is loose or the machine is vibrating.

I'm beginning to beleive that ,because the Mdd is localized to areas such as the lips (not accross the profile), the MDD might be caused by the releif on the hubs not having the proper internal radiuses or the dies not having the proper extenal radiuses in the areas affected. The coins are beginng to show me this by how the metal appears around the affected areas.
Thanks, Bill