Is hairline chatter related to metal flow?

The following three coins are all certified by PCGS at MS66, and they are fairly representative examples of coins minted in their respective decades.

The first one exhibits a great deal of chatter around the rim - something you see often in the 70's and 80's, particularly in P-mint coins.



In the 90's, the mint moves to a lower relief on this series, particularly concerning the high points of the cheek on the obverse and shield on the reverse. From 1992 on, there is generally still some chatter, but it's significantly reduced.



By the time the satin finish collector coins come out, the chatter is all but eliminated.




Now I understand that some of the hits on the earlier coins can be attributed to the packaging process, but my question is: can the striking process actually cause hairline fractures in the field?

Notice the concentration of chatter around the date of the 71-P, where it's weakly-struck. I've seen this pattern a number of times. Is it coincidence, or does a lower striking pressure in a particular area actually induce the micro-fractures in the field?

 

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The chatter you are referring to is caused by the annealing process which takes place before the actual striking of the coin. Its caused because CuNi clad coins are very hard and if not struck hard enough the annealing marks do not go away.

 

Thanks Matthew. Do you know if the annealing process changes at all from the 70's to current, or is the diminution of chatter a result of lower profiles and stronger striking pressure?

 

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Not really sure as im not an expert just asked the same question once and that was the answer i was given. Its important to know cause some coins given a high grade with such marks can be very confusing, whats important is separating annealing marks from bag marks. Bag marks typically show the reeded edge of another coin...

 

Yes, I watched a video of the process and that's exactly what I saw as far as the annealing furnaces are concerned. But Matthew's point that the hairlines are caused before the strike is still valid I think. The punching, rims, washing, tumble polishing, and machine sorting must take its toll.

So there is a correlation between weakly-struck areas of the device and the concentration of hairlines in the fields of those areas - but it's not a matter of metal flow, but rather lack thereof.

 

You should watch this maybe????

http://www.youtube.com/watch?v=7jggPpaLyKk

 

Interesting. That annealing furnace was very different from the one I saw. The planchets certainly did get tumbled around. I watched the process of making proofs, which is obviously different than business strikes. In the case of proofs, the planchets did in fact ride on conveyor belts through the annealing furnace without touching each other, as Doug mentioned.

http://www.youtube.com/watch?v=Y0gR9Fn5qsQ

(FF to 1:00 - annoying introduction.)

 

Ok, thank you very much for the clarifications Doug!

 

I'm gonna disagree with you Doug. Annealing "may" have occured with trays in the old days but certainly not during todays mass production of millions of coins. Strictly speaking post 1965 when the copper nickel planchets were introduced and more specifically with the CnClad Kennedy Half and Eisenhower Dollars.

The "chatter" the OP is referring to is most certainly introduced during the annealing phase and as such, that chatter, which is most prominent near the edges of the struck coin, can be struck out with good metal flow during the striking process. Metal flow is the direct result of striking pressures and for the CnClad coins, increased striking pressures caused premature die failure. Dialing down the striking pressures produced enough detail for the coin to meet spec but left that annealing chatter near the edges of the coin. Poor metal flow also leaves this chatter in the high points of the coins as well. Namely the cheek and chin areas. This is one of the reasons that these CnClad coins look so terrible.

No doubt, during the pre-strike manufacturing process, planchets are tumbled enough to create these hits which are most evident on the Philadelphia IKE's and Kennedy's. The Denver Facility had a die repair shop but lacked the ability to create dies in the 70's. As such, damaged dies were "repaired" until no longer serviceable. These repairs are quite evident on the Eisenhower Dollars from Denver.

Notice the flattened Date on the OP's coin. This is quite common on these CnClad coins and is a direct result of lower striking pressures.

The manufacturing of die's AND coin's changed dramatically when silver was replaced with the much harder CnClad media. The end result reflects that difference in the form of planchet chatter commonly referred to as annealing chatter. It exists oin virtually every coin the US Mint produces with the exception of special collector coins (i.e. Satin Finish and Proofs)

Below is a lightweight Silver Clad Eisenhower which shows evidence of this chatter.



Since the above coin is 1.5 grams lighter than spec, it can be assumed that the planchet was thinner than the norm. A thinner planchet creates a weaker strike with the net result being the chatter is not removed due to incomplete metal flow.

To address the high point chatter problems, the US Mint toned down the relief of the Kennedy Hald Dollar over a series of years creating the now, nearly flat coins that we see today. In 1972, the US Mint started experimenting with harder die steel so that pressures could be adjusted to accomodate the harder planchets. The net result shows up with the 1974 and later IKE's in that MS67 is fairly rare until that time.

Ti make a boring story short, I'd summarize by saying that the manufacturing processes changes significantly when CnClad was introduced to step up coin production.

 

I appreciate your expertise as always, Lee.

 

truth be told, I'd always heard of annealing ovens and annealing drums but after Dougs post, looked it up in the Error Coins Encyclopedia.

Sure enough, there's a picture of a tray in the oven. But, its a tray of dies, not coins. It's also an old photo but it did get me to thinking. The video definitely shows a drum as the planchets are spilled toward the quenching bath. Whether or not that is an annealing drum or not is unclear from the video.



Most assuredly, coins do touch each other during all phases of the manufacturing process with the exception of the striking process. Sometimes even then though.

 

Just admit it Doug you were wrong, providing links that have nothing to do with the U.S. Mint is weak. You know and i know that some marks on a the coin happen before the strike and sometimes are not completely removed, that is all john wanted to know about.

 

I dont know maybe you missed it? http://www.youtube.com/watch?v=7jggPpaLyKk and i think the annealing process would include the wash in the tumbler after i mean a process includes more than one step. You seem to be hung up on the furnace and ignoring the fact that in order to properly anneal the coins they wash and tumble them. All im saying is that the process of annealing the planchets is what causes these marks i dont really care if you want to believe that or not but during the annealing process the coins do indeed touch each other maybe not in the furnace but on the way in and out.

 

I did not mean for you to take it personally Doug at all and am sorry if you took it that way, I meant no disrespect just disagree thats all....