Need a little help on this

The fact that they're adjacent on the Periodic Table was just an immediate hint that, planchet size being equal, whether the clad was present or not wouldn't have much bearing on weight. My second post was the numbers I researched to back up that intuitive truth.

 

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I apologize, Just having a little fun with Chemistry and probably should have added a smiley face. While there are relationships between the Atomic number (number on the periodic table) and properties, a direct correlation isn’t always true. It works for the theoretical density of #28 Nickel (8.92 g/cc) and #29 Copper (8.91 g/cc), but copper density is approx. 125% greater than that of #30 Zinc and #12 Magnesium is approx. 63% of that of #13 Aluminum.


The densities of commercially available copper, nickel, and the 75%Cu/25%Ni alloy are all around 8.91-8.95 g/cc, so I agree with you that a clad planchet and copper planchet of the same thickness would be about the same weight I also agree that it’s a big “IF”, whether it is even possible for an excess copper runout layer to make it through the rolling process and be punched to the correct thickness. My personal feeling is that simplest explanation is usually the correct explanation and this is not a pure copper quarter sized planchet, but it’s hard to certain with these pics.

 

But the layers are not rolled out individually and then bonded together. They are bonded into an ingot and then that ingot is rolled out by being passed back and forth between the rollers. The pure copper, being more malleable than the coppernickel, will tend to "ooze" out the end of the strip. The copper nickel layers may or may not stay even at the ends. Now these ends of the strip are normally cut off before the strip is blanked so you have a nice consistent strip with a copper core and two coppernickel layers each of which is roughly of quarter of the weight of the strip.

Now if they don't cut that strip end off it could be possible to have a section that is just copper and one layer of coppernickel that has blanks punched from it. Such an area MAY be the same thickness as the normal strip but will usually be thinner. (The ends of the strip taper in thickness, another reason why they are cut off before blanking)

 

No smiley necessary; it made for a teaching moment anyway.

Honestly, the difference in atomic mass between the two is why I ended up looking for actual calculations; that difference between Ni and Cu is far larger than the difference between Ni, Co and Fe, for instance. It's not a large difference when Ag is 70% heavier (as an example), but worth exploring in case I'd just stuck my foot in my mouth.

 

All this looks a little overworked. The "Red Book" shows the clad quarter weight as 5.67. You don't have to thank me.

 

5.67 gms is for a quarter made from the CuNi25/Cu/CuNi25 clad. It was proposed that this blank could be the copper core that was rolled to the correct thickness for a quarter (possible, but a long shot). One way to confirm it, is to ccalculate the weight of a pure copper planchet of the correct thickness vs a cald blank (5.67 gms as listed in the redbook). In this case, the CuNi25 outside layers and Copper core have approx. the same density, so the weight of a copper planchet would be very similar to a clad planchet. Metals and metal alloys have wide ranges in density, and until this thread, I didn’t know that Ni, Cu and CuNi25 were nearly the same. This makes the math easy.

 

If you do the math you get a theoretical weight for a pure copper quarter being 5.69 grams. Since the mint tolerance range is +/- .227 grams. that .02 gram difference is pretty meaningless.