What causes this?

1983 Lincoln, tons of die scratches but i am curious how it would get so many. thanks

 

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Polishing the dies.

 

I was thinking that it might be that they were trying to clean the die rather than polish it. We often see Lincoln cents that were struck by grease-filled dies, and the rough lines may have been created by a wire brush used to remove foreign matter.

Chris

 

Yeah I don't think polishing would create scratches. I'd say they would remove them, isn't that what polishing is for? I could be wrong, but I'm kinda leaning more towards Chris.

 

possibly a rough filing of the die to get rid if clash marks...

 

Step back for a moment and contemplate just how "large" those lines are in the context of a die 19mm in diameter. They're tiny. The die will be annealed to soften it before this polishing, and then hardened prior to its' return to production, and there's time pressure to get the die working which precludes the microscopic concentration necessary to completely remove the lines. It was quite possibly the victim of clashing, and the aim of treating that is not necessarily to remove the evidence but to remove "hot spots" of stress from striking pressure which could cause premature failure. It's well-known that the individual design of a die causes unique stress points that lead to early failure - look at the commonality of certain die cracks on certain issues - and additional "detail" on a die throws off the design compromises made to improve die life.

 

AFAIK, professional grading/authentication instructors call those lines "Die Polish." It does not matter if they were put on the die to clean it, refinish it, remove clash marks, rust, or damage. None of them were at the Mint watching at the time although some of the lucky ones have actually seen it done - in one possibly rare (?) case with emery paper while the die was still in the press!

 

I call them die polish lines.

 

Never knew Abe had a nose ring.

 

The dies are NOT annealed prior to polishing.

 

Correct me if I'm wrong, my thinking is that the working dies are annealed to soften them before being struck with the working hub, and annealed or tempered again after being polished and struck with the working hub. After this the only maintenance done to the dies would be polishing to remove any damage from clashes or friction abrasion. The more material that has to be removed, the heavier the medium needed to remove it, then progressing to lighter grits to remove the scratches from the initial grinding. If the mint employee skips a few of the last steps to remove the scratches, they strike coins such as these.

 

Homer, metal is annealed to make it soft. That happens when the dies are being made. You cannot strike coins very long with a soft die.

 

They are also annealed or heat treated to temper them or to make them hard. The difference is the cooling down method or time. Anyway fixed it, maybe.

 

Thank you; that's interesting. I realize it involves extra steps and time taken, but one would think that softening the die would make polishing a lot easier. Otherwise you have to remove metal from literally the hardest steel you're capable of creating.

 

They kind of remind me of stretch marks.

 

Different metals are annealed in different ways but it is done to make it soft. Ferrous metal is annealed by letting it cool slowly.
My son tells me that the term annealing has a different meaning in the world of making bullets. I don't understand it all.

 

The dies are annealed to soften them for the hubbing. In the case of the multiple squeeze hubbing the die would again be annealed between hubbings because the hubbing "work hardens" the die.

Once the die hubbing is finished the die is hardened. This results in an oxidation layer on the die faces which is cleaned off and the die is polished/ground (basined) to the proper curvature. The heating/hardening process can result in warping or unevenness in the die faces. The basining results in smooth faces and the proper curvature needed to make the striking more efficient.

If the dies clash or there is another problem the clash is either removed by further polishing/basining if it is mild, or by what the mint refers to as "stoning" where the fields are "scrubbed" with a emery stick with a coarser grade of abbrasive. In both cases this is done without annealing the hardened die

As a general rule you do not anneal and reharden a used die. Hardening the die is the step where it is most likely to fail so if you have one that has survived it once you don't risk it again. Also the use of the die introduces internal stresses that make it even more likely to fail if it is rehardened and annealed. This was especially true in the early years of the mint when the quality of the steel was variable/suspect, and when exact temperatures of the heating of the steel could not be determined accurately

 

Is it possible that a laser is used to clean the die? To program a laser to clean only the field would be fairly easy . On hard or soft metals.

 

Now there's a thought. Laser ablation for cleaning coins... no scratching. Or what about just ultrahigh intensity light?

 

On a sidenote - Great photos, @Ob77 . What equipment are you using?