The research and development team at the Philadelphia Mint has
faced multiple challenges with the 2014 National Baseball Hall of Fame
commemorative coins program.
Two of the major challenges encountered so far are making three
different domed coins with more than adequate die life and
manufacturing sufficient production tooling.
The program entails production of a gold $5 half eagle, silver
dollar and copper-nickel clad half dollar.
The baseball glove obverse for the series will be concave; the
common convex reverse will follow the curvature of a baseball.
As part of its research and development efforts, Mint technical
staff had to resolve dome configurations and design relief issues,
said Steve Antonucci, branch manager for Digital Development, Research
& Development for the U.S. Mint at Philadelphia. (See related
articles in the Nov. 18 issue of Coin World.)
As part of the testing, more than 67,000 experimental strikes had
been executed by Oct. 28, with thousands more pieces expected to be
struck in the weeks ahead. To that October date, testing had primarily
focused on the Uncirculated coins, with testing of Proof pieces
expected in the future.
Antonucci said Nov. 7 that production tooling is currently being
developed to test all denominations up to the approved trial strike phase.
“All Proof denominations will be tested as well,” Antonucci said
by email, “Polished and laser-frosted dies react differently to
striking forces so we need to test every aspect of the baseball
designs (uncirc & proof) to prove out the running tonnages, press
All research and trial strikes are being performed in the new coin
development section of the Philadelphia Mint, Antonucci said. All
coins and dies are stored in vaults with tight inventory control, he said.
Antonucci said he has taken steps to preserve all of the master
tooling as well as select examples of the research dies, blanks and
U.S. Mint officials will determine the disposition of the
materials at the appropriate time, including whether any
representative materials will be presented to the National Numismatic
Collection at the Smithsonian Institution’s National Museum of
Experimental strikes include those using the approved designs and
those using nonsense designs, the latter featuring dies bearing a
shooting pool player on the obverse with an 8-ball that is encircled
by stitching on the reverse to resemble the baseball.
“My technical staff knew we had to create geometry for the obverse
and reverse that had relative levels of complexity, heights of relief,
curvature, and mass,” Antonucci said. “The challenge was in what
design to pick. We did not want to use baseball as the theme [on the
early experimental strikes].
“In an early development meeting including the artists, I
mentioned that we were clearly behind the 8 ball on this project.”
Antonucci said a suggestion was made to use a pool player for the
obverse; Antonucci contributed the suggestion for using the 8-ball reverse.
Antonucci said U.S. Mint Sculptor Engraver Donald Everhart II
sculptured the pool player obverse using traditional sculpturing
methods on a computerized numerically controlled, or CNC, machined
concave basin to get the curvature precise.
U.S. Mint Medallic Sculptor Joseph F. Menna sculptured the convex
8-ball reverse digitally, Antonucci said.
The nonsense and approved designs were used in various
combinations. Experimental blanks included bronze for the silver
dollar and gold $5 strikes in addition to the legislated alloys.
All experimental strikes for the half dollar denomination employed
copper-nickel clad half dollar planchets.
Part of the testing involved different heights of the dome on the
Antonucci said the Mint had concerns during the early experimental
phases over the likelihood of delamination of the copper-nickel clad
layers — the separation of the three layers of metal in the clad composition.
While experimental strikes using the full dome reverse resulted in
poor die life, no delamination occurred, Antonucci said.
Delamination concerns were eliminated when the full dome curvature
on the convex reverse was reduced to a half-dome height for optimal
die life, Antonucci said.
The half dollar’s full dome was 80 percent proportionally to the
height of the dome used on the silver dollar. The half dollar’s half
dome reflects 50 percent of the dome curvature from the full dome
specification, Antonucci said.
Dies, reductions, master tooling
In creating the dies used in striking the various experimental
pieces, Mint technicians used a range of technologies.
A 3-D, noncontact digital scanner captures the surface detail of
the plaster model that has been digitally designed and fabricated. The
scanner constructs a resultant mesh, or surface map, Antonucci said.
Due to the diameter of the plaster models, the 3-D digital scanner
can only capture one small rectangular segment at a time, Antonucci
said. The model is rotated for subsequent scans, he said.
“We repeat this process many times until we have a complete
quilt-like structure of 3-D information,” Antonucci said. “This is
where [what he termed as] the little black targets come into play.
They are essentially 3-D spatial placeholders so that the quilted scan
data can be assembled into one complete model with no deviations
between each scan.
“The multitude of redundant scan points are summarily removed and
the resultant data prepared for the 3-D design phase.”
As part of the testing process for the Uncirculated versions of
the three denominations, the Philadelphia Mint’s technical staff
manufactured CNC-machined working dies directly from digital designs,
the first time this approach was used in production at the U.S. Mint,
“Normally the first stage is a CNC reduction (male). This is also
referred to as the master hub,” Antonucci explained by email. “The
second stage (off the reduction or master hub) is the master die
(female). The third stage (off the master die) is the work hub (male).
The fourth stage (off the work hub) is the work die (female).”
For silver dollar and gold $5 coin production, U.S. Mint personnel
are cutting out two of the steps for manufacturing work dies, by going
directly to hubbing test dies from the CNC reduction, Antonucci said.
“The Mint will employ a single-squeeze hubbing into die steel of
the first stage reduction, which will produce a negative image (or
die) of the designs,” Antonucci said. “In normal production, the CNC
reduction (or master hub) is used to produce the master die in the
negative, and subsequently the working hub in the positive.
“The negative-facing work die exhibits the coin design incuse and
in reverse so that when the planchet is struck, the finished coin
depicts the coin designs in the positive.”
For the production of half dollar work dies, the normal production
sequence will be followed: a CNC reduction, master die, working hubs
and work dies, he said.
Tooling is being manufactured and stockpiled to meet anticipated
demand. The authorization legislation provides for the production and
release in Proof and Uncirculated versions combined of up to 50,000
gold coins, 400,000 silver dollars and 750,000 copper-nickel clad half dollars.
Various design tweaks
During the testing of the approved designs, Mint staff had to
tweak both of the designs.
On the reverse design, adjustments had to be made to the lettering
in their spacing, relief and orientation “to accommodate the curvature
of the spherical ball, with the letters modified to follow the bends,”
Antonucci said. On the obverse, the wheat ears from the original glove
design were removed so they would not be confused as stitching, he said.
During development, the initial obverse glove design used was
smooth. As the development team moved closer to production, a
leather-like texture was applied to the glove to make it look more
authentic, Antonucci said.
“This yielded some unexpected metal flow issues,” he said.
“Accordingly, reverse ball stitching as well as some areas of the
glove required some minor height of relief changes.”
For the Proof versions, the finish on the glove will be a
combination of digital texturing and laser frosting, Antonucci said.
Some challenges are expected with Proof polishing techniques because
of the unusual contours of both the obverse and reverse, he added.
Mint production sites
U.S. Mint spokesman Michael White confirms that the Proof and
Uncirculated gold coins will be struck at the West Point Mint and bear
the W Mint mark. The Philadelphia Mint will strike the Proof and
Uncirculated silver dollars, which will bear the P Mint mark. The
Proof copper-nickel clad half dollars will be struck at the San
Francisco Mint and bear the S Mint mark. The Denver Mint will strike
the Uncirculated half dollar, which will bear the D Mint mark.
Blanks for the Proof and Uncirculated gold $5 coins and silver
dollars will be hand-fed into the coinage press.
The half dollar blanks are set to be positioned between the
obverse and reverse dies employing an automated feeding approach. ■