Rotated Die question... anyone know?
AskRaq
Posts: 2,303
Okay, as I understand it the mint tolerance on die rotation is just under 30 degrees (27?), so I am assuming that if they are more than 30 degrees, they will get designated as "Die Rotation XX degrees".
Now, here's my question: Are the designations ONLY up to 180 degrees?
An example: if the reverse of two coins is each rotated 90 degrees exactly, with one pointing to 9 o'clock and the other pointing to 3 o'clock - are they both 90 degree rotations?
Or is one 90 degrees & the other 210 degrees?
If they are different, then in which direction are the degrees counted ? (Clockwise, or counter-clockwise?)
Thanks in advance to anyone who knows!!
Now, here's my question: Are the designations ONLY up to 180 degrees?
An example: if the reverse of two coins is each rotated 90 degrees exactly, with one pointing to 9 o'clock and the other pointing to 3 o'clock - are they both 90 degree rotations?
Or is one 90 degrees & the other 210 degrees?
If they are different, then in which direction are the degrees counted ? (Clockwise, or counter-clockwise?)
Thanks in advance to anyone who knows!!
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Comments
Most collectors do not seem interested in examples with less than 30° of rotation, although a small number of specialists may well be. There is no official protocol for measuring the amount of rotation, but as you pointed out, it does convey more information to specifiy rotations as 'clockwise' or 'counterclockwise' up to 180°. Therefore, a rotation of 90° CW is completely different from one of 90° CCW. Many tend to refer to these anomolies as "Rotated Reverse Die" examples, always assuming a proper alignment of the obverse die, but generally we do not know that, so we must refer to them as "Rotated Dies".
Two similar devices have been manufactured over the years to enable accurate measurement of the relative rotation of the dies. The “Rota Die” device was comprised of three sandwiched layers of clear Plexiglas®, with the middle layer cut with a “V” slot. The coin was inserted into the Rota Die device, into the self-centering V-slot, and turned until the obverse die was properly aligned upright. The device was then turned around, and the amount of rotation of the reverse die could be read directly from the back of the device, which incorporated a protractor graduated in degrees. Unfortunately, the ‘Rota Die’ device is no longer manufactured, and is rarely available in the after market. A similar device is manufactured by Leroy Van Allen, well known in silver dollar circles. His device (‘Rota Flip’) is very similar, but is constructed of a soft vinyl plastic fold-over piece that envelops the coin. Then, another vinyl piece is placed over the first, held merely by static electricity, which allows direct reading of the rotation of the reverse die relative to the obverse. One significant advantage of this device over the ‘Rota Die’ is that measurements may be taken on coins while still in any type of holder, whether it be a slab, cardboard 2”x 2” or other holder; the Rota Die required that the coin be ‘raw’ in order to be inserted into the device.
There is a small following of collectors of these mint errors, with a website where they publish a list, by denomination, of all known examples.
http://www.rotateddies.com/
I am not a member of the organization, nor do I know much about them. I simply stumbled upon it while researching rotated dies. I will say that they are completely nonresponsive to any communication, as I have attempted to update their list of rotated die Liberty Seated half dimes several times with no response. They list seven examples, although the first three and the last two are the same die marriage but with differing rotations. I have documented thirty-two different examples for the Liberty Seated half dimes, yet their site does not reflect this new information.
Hope this helps.
From what you said, I take it that "die rotation" does indeed stop at 180 degrees?? But that there is no "orientation" recognized?
Here is a second question:
When a coin is minted (as in the new presidential series, where the obverse changes), there is one non-moving die & one moving die... isn't the "reverse" die always the base die which does not move, and the obverse die the one that "stamps" down on it? And if so, wouldn't that make it an "Obverse Die Rotation"? (since the other die does not move?
Thanks.
The motion of the dies, both toward and away from each other, during the coining process actually has little to do with die rotation. In all cases, the dies are intended to be secured into the coining press either by set screws or a keyway, or both, intended to prevent die rotation as well as secure the die into the press. For the hammer (upper) die, without set screws the die would fall out of the press simply from the attraction of gravity.
If the set screws become loose on the hammer die, the die may eventually fall out of the press. However, if the set screws become loose for the anvil (lower) die, the die will likely remain in the coining press, but may rotate randomly with each successive striking. This would account for the numerous and random die orientations seen on the 1839-O V3 Liberty Seated half dime, for instance. There are also other examples of the same phenomenon.
If a die is inserted and properly secured into the coining press at the wrong orientation, assuming that the set screws are tight, all examples of die rotation will be the same - incorrect, but the same. This is actually a more common phenomenon, and accounts for the well known examples such as the 1844-O V2 or the 1857 V10, almost always seen with 180° and 170° rotation, respectively.
There is nothing in the coining press mechanism that would prevent the dies from being improperly oriented, nor is there anything that would limit the amount of rotation to 180° in either direction. We merely like to specify the rotation as either CW or CCW in order to convey a more accurate description of the struck coin.
So die rotation is essentially completely independent of the obverse/reverse, or hammer/anvil, relationship in the press. Again, both dies 'move' in order to strike a coin, but this has little bearing on whether either die is incorrectly rotated relative to the other. The die rotation is determined by the coiner when he installs the dies into the coining press. Remember that the surface of the dies present a 'negative' image of the coin design, all lettering is reversed, and for United States coins, with 'coin rotation', the dies must be installed into the press with a 180° orientation to each other. It is little wonder, then, that there are a few such errors seen. I often wonder how they ever got it right.
It is a much more rare occurence with the modern coining techniques.
Thanks,
Bill
myurl http://www.foundinrolls.com
The early dies were round with a dimple in the side for a setscrew. If the screw loosens the die can rotate. (If it is the upper die and gets too loose it can fall out, which makes it less likely that the hammer die is the one that rotated.)
Later when they did dual die presses the dies were for awhile cylinders that had a larger D shaped base. The flats of the two bases would be placed together and that would lock the dies in place to keep them from rotating. (This had the disadvantage that the reverse die body itself could break into an upper and lower piece with the lower part locked in place but the upper half free to rotate.) At another time the die bodies were made larger in diameter with large flats and the die bodies themselves were locked together. This eliminated the problem of the die body breacking and then rotating because the upper half would still be locked in place with its neighbor.
Today the die body is a cylinder with a small flat ground along the length of the die which is keyed with the die holder. But the die bodies are turned on a lathe to the cylinder shape and then the flats are ground onto the body by hand. Grind the flat in the wrong place and even though the die doesn't rotate the die face is already rotated in relation to the other die. (The 15 degree tolerance allowed for rotation is due to the natural tendancy for theflats to be ground in slightly different places from one die to the next.)
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good one to post on the q&a forum............................if they ever take more than one at a time.