Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1894-01-18
OLD AND NEW COMING.
How Medals Are Struck By Modern
Machinery.


The striking of medals in the coin
ers department Of the United States
mint has for years been by means
of the screw and fly press, says the
Philadelphia Telegraph. The screw
in this press is six inches in diameter,
and there are ttree threads with
pitch of three inches. The double
lever attached 10 the head OF the screw
is thirteen inches III length or SIX ano
one-haIf feet either way from the
center of the screw, and upon the ends
of the arms are mounted balls weigh
ing about 100 pounds each.
Three men are employed i'll the work
ing Of the press, one to arrange the
blanks to be struck upon or between
the two hardened steel dies, while one
at each cad of the lever furnish the
power to raise the screw and then by
a rapid movement cause the same to
descend to the work, they being careful
al the proper moment to step aside
to avoid being struck by the recoil of
the lever. Two and one-half revOlUl-
tons of the screw give with all the
pressure equivalent to $50 to2s.
In the striking Of i four-inch diane
ter medal some fifty or sixty blows
are necessary to complete the medal.
The blank, which becomes hardened by
the force of each blow, must be an
nealed. Each time, consequently, the
amount of labor bestowed makes the
cost Of such medals quite high.
Some nineteen years since the idea
was conceived that the Introduction by
hydraulic pressure would be more
satisfactory and produce better results
both as to cost and execution. The
trial that was then made on an Ordia-
airy hydraulic press, such as is uscti
for forcing the wheels of Il locomotive
on the axle, was made at the machine
WOrkes Of William Sellers & Co. An
accident occurring in the bursting of
the steel collar, by which the then
Coiner of the Mint was injured, had
a dampening effect upon the scheme,
though the idea never met with en-
couragem4llt until some two years
since, when an opportunity was offer
ed to make the test of the preSsureS
required to make the various coins.
This being so satisfactory, and having
gained the conclusive knowledge that
or years had been only guessWork,
Il encouraged the revival of the idea,
and plans and estimates were framed
FOR q press that should have capacity
or striking pressure equivalent to
1000 tons.
The contract for this press was
awarded to NTessrs. William Sellers q
Co at Il cost of 1000. The designs
having been approved, the press was
completed in September, and upon trial
at the works the result was most sat
isfactory. The dies used upon the trial
were those of the 4-inch General
Grant medal. The blanks were sub
mitted to pressure OF 100000
pounds. and the second pressure after
the annealing of the blank almost fin
ished the medal. One blank upon
which the pressure was CXerted three
times in succession was found to have
had more than was necessary.
The press is complete in detail and
symmetrical i'll design; it is an arch OF
oval in form, the base and head being
secured by two cast steel bands inch
eS thick ana inches wide. These
bands were submitted to Il strain of
100000 pounds each before being
put III place. The ram is located i'll
the upper or head casting, and is plac-
Ell in Il steel case. 1t is 70 lncheS III
diameter, and the maximum pressure
OF 1900 pounds per square men gives
pn this area the pressure OF 1000 tons.
There is Il graduated device attached
by which any desired pressure can be
secured and held for any length OF
time Experiments will soon enable
the person in charge of the press TO
determine the amount of pressure re-
Quired for the various sizes of medal.
The movement of the ram up and
down is simply by the pressure of the
oil from the tank, situated about tif-
teen feet above the room, the maxi
mum pressure being supplied by a
thin throw pump, and is only eXerted
during about the last half inch OF the
stroke of the ram.
The power to drive the pump is sup
piled by means of Il { Ii horsepower
Eddy electric motor of Il slow speed
type. For the annealing OF blanks
there is small gas oven, and 1T IS
tery satisfactory. 1t has been demon
strated by the experiments already
made that the pressure of 10000 pounds
per square inch is required to cause
such metals as gold, silver and copper
to commence to flow or become fluid.
Very interesting results are expected
from the Installment of this plant,
which will add so much to the advant-
age of the government.