Dimensions of pre-1964 silver coinage BLANKS 1 1

[Mike824]

Hello,

I'm looking for the dimensions of pre-1964 coin blanks, the circumference and height specifically. What started out as a simple/not-so-simple math question: Find the weight of a 1964 Kennedy Half Dollar using the density of silver and copper, and it's radius and height. Fairly straight forward, all the info you need to solve the problem is easily found with a quick Google search. 

Density of Silver: 10.49 g/cm^3
Density of Copper: 8.94 g/cm^3

Volume of the 1964 Kennedy: 1.58cm^3 = 3.14156*15.31*15.31*2.15 = 1583.2mm^3 = 1.5832cm^3

Weight/Mass(Earth) then comes down to the formula Mass = Density x Volume: 1.5832*0.9*10.49 + 1.5832*0.1*8.96 = 14.947+1.485 = 16.365g

So the weight of a 1964 Kennedy Half Dollar is 16.365g. Except it's not, it's 12.5g. Turns out the math is right, but the inputs were not.

Sooo... I need to find the dimensions of the blanks used to produce the 1964 Kennedy Half Dollars. And that has not been an easy Google search. Can anyone tell me what the dimensions of the blanks used to produce the pre-1964 coinage is and the source?

Thanks

[Mr.Bill347]

Mike824, I was able to find these examples on NGC collectors society page, from a member named bonehead.

I think you’ll find everything you need here, good luck.

[Mike824]

Thanks for the search, but what I need are the dimensions of the blank, specifically circumference/radius and height.

[JKK]

I recommend using the proper terms for the metal disks that are struck with dies to produce coins: planchet (most modern) or flan (generally more archaic). We know what you mean, but it never harms the cause to get the terminology correct. I would not have expected you to know this, so none of this is criticism--just education.

[EagleRJO]

The attached ledger data from the US mint in the 1930s may help, courtesy of @RWB

 

Edited December 23, 2022 by EagleRJO

[Mike824]

On 12/22/2022 at 2:07 AM, JKK said:

I recommend using the proper terms for the metal disks that are struck with dies to produce coins: planchet (most modern) or flan (generally more archaic). We know what you mean, but it never harms the cause to get the terminology correct. I would not have expected you to know this, so none of this is criticism--just education.

@JKK I appreciate your response, but Blank is the correct term. The metal disk is called a Blank when punched from the roll. It becomes a Planchet when it goes through the annealing and upsetting process. Upsetting is where the coin to be gets a rim and the dimensions are first changed. I need the dimensions of the Blank before it becomes a Planchet.

[Mike824]

On 12/22/2022 at 4:51 AM, EagleRJO said:

The attached ledger data from the 1930s may help

@EagleRJO PERFECT! Thank you!

[JKK]

On 12/22/2022 at 3:58 AM, Mike824 said:

@JKK I appreciate your response, but Blank is the correct term. The metal disk is called a Blank when punched from the roll. It becomes a Planchet when it goes through the annealing and upsetting process. Upsetting is where the coin to be gets a rim and the dimensions are first changed. I need the dimensions of the Blank before it becomes a Planchet.

Ah. Thank you for sharing that understanding, and please pardon my mistake.

[RWB]

Diameter and thickness of a cut/punched blank were not legally specified values. They varied with the fixed diameter of a coin , and the variable angle and height of upset necessary to produce a legal coin, free of defects, from the working dies available at any specific time. The notebook pages EagleRJO posted are from my research files.

Edited December 23, 2022 by RWB

[EagleRJO]

On 12/22/2022 at 8:53 PM, RWB said:

The notebook pages EagleRJO posted are from my research files.

@RWBI should have credited the source ... corrected.

[B.C]

On 12/21/2022 at 6:09 PM, Mr.Bill347 said:

Mike824, I was able to find these examples on NGC collectors society page, from a member named bonehead.

I think you’ll find everything you need here, good luck.

 

On 12/22/2022 at 3:58 AM, Mike824 said:

. It becomes a Planchet when it goes through the annealing and upsetting process. Upsetting is where the coin to be gets a rim and the dimensions are first changed. I need the dimensions of the Blank before it becomes a Planchet.

Actually annealing happens before you move metal so In the case of a 64 a silver billet is poured then annealed (softened) before turning said billet into a sheet 

Type 1s were annealed before they were born

Mike a blank has a tapered edge from the press it's like cutting a fresh loaf of white bread that Dosent spring back up gonna be hard to calculate and then the weight loss in the reeding and upsetting if that helps complicate your easy math problem even more 

 

[Fenntucky Mike]

On 12/22/2022 at 4:51 AM, EagleRJO said:

The attached ledger data from the US mint in the 1930s may help, courtesy of @RWB

 

Is this applicable to 1964 halves? I see that the "finished" diameter matches, or is very close to today's halves but are the blank dimensions the same, then and now? Probably.

Interesting that there were three corrections made, 1.203, then down to 1.195, down to 1.185 and back up to 1.195.

Edited December 24, 2022 by Fenntucky Mike

[RWB]

The diameters of blanks will vary much as I described above. It is an engineering quantity, not a legal one. The value given for WL halves is as good as any.

Edited December 24, 2022 by RWB