Tapering and thinning of devices

[VAB2013]

I have read Will's thread "Tapering/thinning of peripheral devices" and even though it was regarding 1996D's from mint sets, Will does describe seeing this anomaly on other cents as well.

I can see how tapering and thinning of devices can be due to an incomplete hubbing... but not really from over polishing of the die. I can also see how this thinning can be caused from a grease filled die since the grease and gunk gets into the recesses of the incuse area of the die.

The reason I can't see it being caused by over polishing of the die is... it seems like since the devices are incuse on the die that over polishing would make the devices thicker and wider... not thinner. Unless, the polishing actually moves enough metal around and it starts to fill in the void of the incuse devices. If so, how can it do that with such accuracy as we see on the affected devices where this thinning occurs? I may have just answered my own question? Not sure?

At the same time, I can understand why die deterioration can cause the devices to become thicker and mushy looking due to excessive wear to the edges of the incuse devices on the die.

[jfines69]

Looking at the animated 3D rendering you will notice that the outer edge of the die is being worn away actually removing parts of the lettering closest to the edge... As the metal is removed the devices get thinner... We can actually see what looks like a ridge ring developing but as Will points out the ridge ring is developed thru die wear throughout the dies life and the thinning in this area is the result of an over zealous polisher in training Why the die would be so aggressively polished before being put into service is beyond me... Hope that helps a bit!!!

[VAB2013]

Thank you Jim for this explanation, and it does make sense to me now on the edges of the devices near the rim. What about in a case like the 1983's we see when the Y of Liberty is very small in comparison to the rest of Liberty?

[GrumpyEd]

Viv,

If you could see a crass section (like the cool ones Ray makes!) showing most devices they would look like pyramids, wider at the base and narrower at the top. Then think of the die, the base part is the surface of the die, the top narrow part is the deepest part. As you polish or grind away the surface, it removes the wide base part and what is left is a smaller pyramid shape.


Then think of a partly filled die, the top highest part is easiest to get clogged up so they will look flatter.

Then think of die wear, the die wears away making a mushy ramp at the edge of the devices so if you had a cross section the pyramids base gets wider.


I think the ones that get harder to envision are the smaller TY of liberty or when the top horizontal bar of the T in states gets really thin but not the vertical bar. Those might be that the hubbing wasn't full or level in the first place or it may be that what we see as the flat top of those devices is sort of flat but not really flat so some area was slightly deeper so after polishing only that deepest part shows.

[VAB2013]

This absolutely makes sense to me, thank you Ed! I would have never thought about the incuse devices on the die having a pyramid like depth to them. The light bulb just came on

[jfines69]

The Edcyclopedia of Coins... Thanks Ed... I totally forgot about the pyramid shape!!!