Press pressure used to strike coins, and how it was regulated – 1901
RWB
Posts: 8,082 ✭
Someone here or on the NGC board asked for this information a while ago, and I just came across the following. Denomination on the left, pressure in tons/sq inch on the right.
$20 – 155
$10 – 110
$5 – 60
$2.50 – 35
$1 silver – 160
Half – 98
Quarter – 60
Dime – 35
Nickel – 60
Cent – 40
Measurements were made using a spring gauge and are likely +/- 5% or more off. Based on other sources, I suspect the $20, $10 and $1 are too high by about 30 tons.
Pressure on the electric coinage presses was varied by changing the amperage of the current. The mint used graphs based on experiments with each press type to determine correct striking settings.
$20 – 155
$10 – 110
$5 – 60
$2.50 – 35
$1 silver – 160
Half – 98
Quarter – 60
Dime – 35
Nickel – 60
Cent – 40
Measurements were made using a spring gauge and are likely +/- 5% or more off. Based on other sources, I suspect the $20, $10 and $1 are too high by about 30 tons.
Pressure on the electric coinage presses was varied by changing the amperage of the current. The mint used graphs based on experiments with each press type to determine correct striking settings.
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Comments
Nothing surprises me except the large gold. These seem quite excessive.
In Q. David Bowers book "United States Gold Coins An Illustrated History"
he states the same coin press pressures used for the denominations
cited by RWB. These were in a discussion of the new presses used at the
new Philadelphia Mint building beginning in 1901 built by T.C. Dill Machine Co.
Bowers also mentions in the medal room, there were two electrically driven
hydraulic presses capable of pressures of 400 and 300 tons to the square inch.
In the basement there was a larger press capable of giving 1,100 tons pressure
to the square inch, which was used on the largest dies of four inches in
diameter.
In an 1896 "Report of the Director of the Mint," Bowers states the following
regarding striking gold coins (using I assume the Morgan, Orr & Co. presses):
$20 - 175 tons
$10 - 120 tons
$5 - 75 tons
$2.50 - 40 tons
The top two being struck at 80/min. & the bottom two at 100/min.
R.I.P. Bear
Fasinating.Thanks for the historic information.