Minting Press Tonnage Calculation Question - Page 2
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  1. #21
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    Quote Originally Posted by 4GSR View Post
    You already live in a country separate from the union...it is called "TEXAS" How much more can you ask for?
    Ohhh, dude. If Texas is a separate country, Austin is a separate planet.

    Asif, minting your own gold and silver is fine, but to be useful in the coming zombie apocolypes, you'd be better off having stuff made by a sovereign nation. That way, the assay is pretty well known.

  2. #22
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    I always thought that the area of a circle is pi r squared
    and the circumference was pi d

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    Shire Post Mint is pretty well known, mintage lists are published, and assays guaranteed. I even "tag" some of my alloys with exotic elements so that they can be traced to me, even if remelted and reformed. Shire Post bullion types, such as the Game of Thrones silver stags and silver moons are ALWAYS slightly overweight. The 1/10 oz stags weigh at least 3.2 grams, up to sometimes 3.4 grams. We are well enough known in the geek world that our reputation exceeds that of many of the smaller sovereign nations. We do many of the strikes for Blue Waters Mint as well. So these are fantasies... but in real metal and with known low mintages and collectible catalogued die-types. There are over ten pages of our coins listed in Krause Publications UNUSUAL WORLD COINS.


    Quote Originally Posted by bosleyjr View Post
    Ohhh, dude. If Texas is a separate country, Austin is a separate planet.

    Asif, minting your own gold and silver is fine, but to be useful in the coming zombie apocolypes, you'd be better off having stuff made by a sovereign nation. That way, the assay is pretty well known.

  4. #24
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    Texas I thought was a country, WE rented a lot of presidents from there.............

  5. Likes 4GSR liked this post
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    Default Coining Press

    Sir, I am in the Austin area and I am looking for a 100 ton press to make coins with along with any other information I can find.

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    Hey Good Buddy, formula you used (pi D square) is for circumference, the formula you want is: (pi R square) which results are 3.09 sq inches...... now start over from there

  8. #27
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    I'm a layman wanting to press my own coins. I researched a basic formula for how much tonnage is required to press coins of gold and silver, and the calculation came out to be like this:

    Diameter = 50 mm = 1.97 inches.
    Area = 1.97 x 3.14 = 6.1858 sq inches
    Silver Density = 10.5 grams / cm cube = 172 grams / inch cube
    Thickness of a 60 gram silver Coin = 0.057 inches
    Ultimate Tensile Strength of silver = 20300 pounds per sq inches = 9.2 tons per sq inch
    Force required = 6.1858 x 0.057 x 9.2 = 3.2 tons.

    However, this 3.2 tons is far less than what professionals in the industry tell me. E.g. Kempler guy suggested that I would need this
    63 ton Maypress to be able to mint coins.

    USED 63 TON MAYPRES COINING PRESS - Kempler Industries

    So my question is, why is the "theoretical" calculation coming to be so low, and why in real life a much higher tonnage is needed?

    Will I totally not be able to press coins from a 4 ton press? Or would it make a difference on the quality etc.?

    Thanks
    Asif

    Got the wrong formula: (pi D) is circumference, (pi R sq) is area.... area of a coin 1.97" in Diameter equals 3.09 or therebouts. Might want to start over with your equation.

  9. #28
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    Panama Tom's post brings me back to Carol Boyd's post. One of the first courses taught in the Chemical Engineering curriculum is dimensional analysis. It is an extremely powerful tool for checking your work, and can actually be be used to derive formulae by getting the units on both sides of the equation the same. In some cases, some hairy calculus can be avoided with simple unit cross cancellation.

    Gibbing's book on the subject runs to 297 pages.

    A recent "this old tony" video goes into it a little bit. YouTube

    He gets grams/pound numerically wrong, but it is a nice example of the technique. Especially the conversions between mass and force units. There unit of mass in the english system of units is actually called the slug, and that is his lbf s^2/ft. Slug (unit) - Wikipedia

  10. #29
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    I was in a guy's shop who made every Washington State Patrol badge for over 100 years. They used huge drop forges.

    4 tons? No way in the world.

  11. #30
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    Basically every reply on force needed is wrong. It has nothing to do with UTS, yield or shear strength. It is totally and only dependent on the flow stress of the material at the temperature you are coining and the projected area of the coining, including any flash beyond the coin diameter.

    Flow stress is not a concept most people are familiar with. The concept isn't even covered in your first mechanical engineering degree. Simply put, it is the pressure at which any material will flow. It is highly dependent on temperature. Flow stress will continually drop until the material actually melts and becomes liquid. The Greeks and Romans made bronze coins with tiny dies and hammers. I'm sure they didn't do this cold.

    The energy you have available can be converted to increased pressure but is more aptly used to speed up the process.

    I can't tell you what the flow stress vs temperature is for gold and silver but it is published data. You then can make a calculation of forces required and the temp you may want to do it at. Temp will vastly reduce the tonnage necessary.

  12. #31
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    I build hydraulic presses that are used for die striking, we also make coining die sets and ornamental dies. Any kind of coining is going to need 100 tons to start at least for stuff around 1 inch in diameter. If all you want to do is press some lettering in no worries thats easy but raising an image is what takes the tonnage.


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