Anyone collect lathe mark errors.

Peaceman · April 17, 2011 1:31PM

It would seem that this kind of error (Happens on other types too) is rare from the feedback I've received on other boards....

keyman64 · April 17, 2011 1:38PM

Cool, never seen one of those before!

howards · April 17, 2011 4:47PM

There a some dies known for shield nickels (particularly 1866) that show strong lathe lines. They have to be pretty spectacular for me to list them in SNV.

1866 S1-8001

ricko · April 17, 2011 9:31PM

Interesting... have not seen that before. Cheers, RickO

RWB · April 17, 2011 10:29PM

Why are the arcs nearly as stong on the portrait as on the field?

Are these concentric or spiral?

ThePennyLady · April 17, 2011 11:38PM

I have this one and I love it!

pontiacinf · April 17, 2011 11:43PM

had no idea something like that existed, learned something new again

look out, call the contractor, my head is getting so big, gonna have to widen the doorways
at my house just to get in

notwilight · April 17, 2011 11:52PM

If they are no the devices, they are not lathe marks. I would suspect they are polishing marks. The die was spun and a polishing material pushed into it. Remember the devices are recessed in the die so if spun at all fast, it would be difficult for a polishing cloth with grit on it to get down into the devices. I'm puzzled how this happens on the devices.

One possible thought on newer coins is that the die is spun and laser treated. A laser would make marks on both the fields and devices.

I don't think this is likely it it could be that the lathe marks were on the planchet and survived the striking. --jerry

--Jerry

Coppercolor · April 18, 2011 12:07AM

Last year I sold a roll of 1935P Lincolns where about 1/5 of the coins had the lathe marks on Lincolns potrait, kind of like Charmie's. They also had awesome strikes and if they didn't have roll haze I'd have graded them all.

If you look at the Stewart blay 1935 in PCGS 68RD you can see them there as well. Blay 1935P Lincoln
I suspect this is an indication of very EDS.

<<Edited to add link>>

19Lyds · April 18, 2011 3:56AM

Lathe marks are the result of machining the "blank die face' to a conical shape prior to being impressed into the Working Hub. As such, they can and often do appear on the coin devices. Depending upon the finishing used on the "blank" dies after lathing, will usually dictate where the lathe lines will show up. Either the entire surface (as demonstrated by the Kennedy) or only on the portrait or out near the edges of the die face.

As for spiral or concentric? I expect a little of both but more than likely a fine spiral.

The OP's Kennedy is Cool and Notable. Is it from the 80's?

MsMorrisine · April 18, 2011 4:15AM

there are some memorial cents that have these.

oh yeah... can we have the year and mint on that Half? So we can keep an eye out for others.

johnny9434 · April 18, 2011 4:16AM

i never remember seeing anything like that before. maybe i just dont remember it. interesting

Nysoto · April 18, 2011 4:49AM

There are four different obverse dies for draped bust half dollars that have fine concentric lines on the lower surfaces of the coin (which are the highest surfaces of the die). These are from polishing marks of the working die, which were done on a lathe in an experimental basis in 1807. Some of the lines will cross one another which is to be expected when the polishing compound is worked across the face of the die.

PerryHall · April 18, 2011 5:08AM

Are these really considered errors?

RWB · April 18, 2011 5:16AM

If the explanations, above, are correct they are significant die varieties, not errors.

dcarr · April 18, 2011 6:49AM

If concentric circular marks are found only on the fields, then the cause is most likely a die polishing effect. I believe the 1866 Shield Nickel shown previously is a die polishing artifact and not lathe marks. The marks only appear on the fields, and they are too irregular to have been caused by a lathe. The other examples shown are lathe mark varieties.

But if the marks cross over the devices, then it is probably due to a reduction lathe artifact. In such a case, the lines would be found on the master hub (or on the central device punch). I've engraved countless dies using the equivalent of a digital reduction lathe, and I've experienced those concentric circular lines (actually a fine spiral). In fact, it seems that things have to be set up just right to avoid getting them.

When I was restoring my Denver Mint surplus Grabener coin press, one of the things I found in the oil pan was a 34mm John Adams President medal (with a"D" mint mark). The die for this medal was apparently made on a reduction lathe from an original 3 inch version of the medal. Since the model was smaller than normal (3" vs. 8" or 9"), the result had softer details and more lathe marks than normal.

Note that the "D" mint mark is sharp because it was created by using a normal "D" punch applied to the die after it was machined. Also note that the same type of machining marks seen in the bottom picture above can also be seen in some places on the big silver ATB "hockey pucks" (like on the designer's initials, for example). This is becaue the large ATB dies are individually machined using a digital reduction lathe process similar to what I use.

Here is an example of one of my dies that had lathe marks. The lines can be seen on Liberty's skirt, and across the arm holding the torch. These lines were caused by inaccuracies on the Z axis of the engraving machine.

PS:
As a side note, it seems the US Mint 34mm bronze President medals with a "D" mint mark are under-appreciated and considerably scarcer than the Philadelphia versions.

Tdec1000 · April 18, 2011 6:57AM

I have a few of 1996 d lincolns with concentric lathe marks!

RWB · April 18, 2011 6:59AM

Mr. Carr's comments make sense. Essentially mechanical errors or inattention, producing the spiral. Somewhat like having the wrong cutting tool or not changing the tool as appropriate; too much haste?

(This was something that was difficult to manage on the Janvier reducing machine. The modern Micron cutting machines are supposed to prevent this by automatically stepping the cutting tools.)

MedalCollector · April 18, 2011 7:20AM

Wow! That is pretty amazing! That is extremely scarce for being that strong, and especially for being a half dollar.
These have been regularly seen on cents and nickles, but rarely on half dollars. Cool find.

Anyone collect lathe mark errors.

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