How the Denver Mint Makes Coins for Circulation

by Darrin Lee Unser on January 13, 2014 · 1 comment

This fourth article in a series about our visit to the U.S. Mint at Denver offers information, photos and videos on the production of circulating coins at the facility.

It’s almost as if visitors to the United States Mint in Denver, Colorado, are subjected to a sort of time warp that takes them from the early 1900’s and then to modern day. In walking up to the building’s front, you see the classic Gothic Renaissance structure and are reminded of the days of old. But inside, a different scene quickly emerges with massive machinery, computers, robotics and operations taking up a city block.

Photos of Denver Mint Coin Production Processes

Some of the equipment and materials used by the U.S. Mint facility in Denver, Colorado to make coins for circulation – More, larger photos below

To appreciate the disparate views put forth by the structure and the processes occurring inside, visitors should consider the public tour which I wrote about earlier. The original Denver Mint building of 1904 is still in use, preserving the impressive grand marble hallway, chandeliers, murals, and even a machine gun nest of yesteryear. However, behind that classic structure, several later year additions speak of its true purpose — manufacture coins of all denominations for general circulation. It is the procedures and equipment of circulating coin production that this article, photos and videos hope to now focus on.

The mechanics of producing coins for circulation is almost identical to that of the Denver Mint’s sister facility in Philadelphia, with a few exceptions. One of the most notable is that the Denver Mint operates in connected structures added in stages throughout the years. This means production lines are not always completely linear. This is not to say that the Denver complex is without practicality. Operations start where they will end, at the loading dock. There, pallets of metal coils are unloaded and then moved to short term storage on racks. It is these coils from which coins for circulation are made.

Nickel Coil Staging Area, Denver Mint

Staging area on the coin production floor for nickel coils

Quarter Coil Staging Area, Denver Mint

Staging area on the coin production floor for quarter coils

Think of the coils as rolls of blank newspaper, only weighing thousands of pounds with each about a foot wide and consisting of 15,000 feet of metal about the thickness of the size of coin to be struck. These heavy coils are loaded as needed to a production line that begins with Blanking Presses.

Blanking Presses Produce Blanks

To begin the coin production process, a coil is fed into a Blanking Press that works like a giant cookie-cutter, punching out blanks at an amazing rate. For instance, in one minute more than 13,200 blanks for dimes can be produced — blanks are the round metal disks that get struck by dies in Coining Presses and become coins.

Coil, Blanks and Scrap

Left: A coil of metal that is fed into a blanking press. Middle: Cut coin blanks. Right: Leftover scraps called webbing.

With the above three photos in mind, the front of a Blanking Press accepts sheets of metal, the middle of it cuts the blanks, and the end of it delivers the desired blanks and leftover scrap called webbing.

To see how it all works, the following photos and videos offer a visual tour of the process.

Coil Fed in Blanking Press, Denver Mint

A metal coil weighing 10,000 pounds is fed into a Blanking Press. One stroke of the press punches out 22 blanks. It takes 45-60 minutes to finish one coil.

This short video shows how quickly the sheet of coil spins and moves inside the Blanking Press, hinting at the speed blanks are made.

 

Directly inside, the sheet is guided into the pressing area.

Sheet Inside of Blanking Press, Denver Mint

The sheet of metal is guided to the press

Now, the Blanking Press cuts the blanks — 22 in one stroke, and its conveyor delivers them. Watch this video to see how quick it all happens and hear the loud punching action of the press.

 

Blanking Press operators, like Freddie Smith, will often inspect the scrap because if there are errors in the blanks, there will be opposite errors in the scrap too, like a puzzle.

Freddie Smith Checking Scrap on Coin Production Floor, Denver Mint

Freddie Smith, holds the scrap metal from the coils used in the blanking process. The material will be sent back to the manufacturer for recycling.


Scrap Coin Webbing from Blanking Press, Denver Mint

This photo shows leftover scrap coin webbing from Blanking Press

Annealing Furnaces and Washing Blanks at Denver Mint

The next stage is for the coin blanks to go through annealing furnaces which both softens the metal and strengthens it. Following their trip through the "oven," the blanks spend a few minutes in a quench tank to cool down before it is time for a bath.

This is one step which differs slightly from the Philadelphia Mint. At the Pennsylvania location, the coins are taken out of the quench tank and into the washing process via whirlaways which spin around transporting the now cooled blanks up the line. In Denver, they are mechanically lifted out of the quench tank to drain before moving on.

Annealing the blanks causes discoloration which now must be removed. To do so, the blanks are cleaned in a washing process that involves chemicals which also aid in brightness and prevents tarnishing. Once complete, the blanks are dried in preparation for upsetting.

Now, another series of photos that shows the steps. First, many of the machines on the production floor are gigantic and it makes it extremely difficult to get photos of them. This photo highlights the height of equipment in the area.

Three-Story Production Height

Three-story equipment height

With that said, here are some photos of the annealing and washing stages.

Gilbert Manzanares, Denver Mint

Gilbert Manzanares, operates the furnace in the automated materials processing area (AMP) on the production floor.


Blanking Furnace AF-03, Denver Mint

This furnace AF-03 reaches temperatures up to 1600 degrees and anneals about 2800 lbs. of nickel blanks in an hour.

Here is a short video of a skip basket with 2-3 gallons of water to wash blanks and drain them. It works like a colander (strainer) and is connected as part of a different furnace, AF 5, which anneals and washes quarter blanks. It handles about 3,000 lbs. of blanks an hour.

 

Moving along, this steam dryer uses steam to dry damp blanks after washing.

Steam Dryer, Denver Mint

This machine can dry up to 3000 lbs. of dime blanks every hour


Blanks at After Production Stages, Denver Mint

From left to right: Blanks after they are annealed, quenched and then washed. Each blank looks and feels different following each stage.

Upsetting Stage to Create Coin Planchets

At this phase, the blanks are flat discs and need to be run through the upsetting mills. These devices create a rim or edge on each piece. This is important as the rim becomes the highest point on the soon-to-be-coin and helps to protect the designs. Not only do the pieces change in appearance after a run through the upsetting mills, they also take on a new name. Technically, they are now coin planchets.

We walked quickly through these areas at the Denver Mint because the machinery was exactly like those of the Philadelphia Mint. The following photos and video are those we took during our private tour of the Philadelphia Mint.

 

Schuler Upsetting Machine at Philadelphia Mint (a)

Schuler Upsetting Machine at Philadelphia Mint. This machine places an edge or rim on blanks.

Schuler Upsetting Machine at Philadelphia Mint (b)

Shown here are the vibrating feeder bowls for the upsetting mills.

Schuler Upsetting Machine at Philadelphia Mint (c)

A closer view of the vibrating feeder bowls for the mills.

Schuler Upsetting Machine at Philadelphia Mint (d)

Schuler Upsetting Machine. This spinning disc quickly forces blanks against a stationary segment which causes the edge to slightly rise.


Planchets

Planchets created from blanks running through an upsetting mill. Notice these metal discs now have edges or rims.

When it comes to making blanks and planchets to produce coins for circulation, the manufacturing steps are the same minus the penny. The United States Mint no longer makes blanks and planchets for Lincoln cents. They are outsourced and delivered to the Denver Mint (and Philadelphia Mint) in bins, like those in the two photos below. The cent planchets in these bins are bottom fed to Coining Presses.

Bins of Lincoln Cent Planchets, Denver Mint

Bins of Lincoln cent planchets at the Denver Mint


Lincoln Cent Planchets, Denver Mint

A closer view of the cent planchets

Coining Presses at Denver Mint to Strike Coins for Circulation

Planchets journey further down the production line, via conveyors, to Coining Presses. It is here that they take on their final form and become coins. To do so, the planchets are fed on demand into the presses.

Overlook of a coin production section at US Mint at Denver

This photo taken from the public tour gallery shows a section of the Denver Mint’s coin production floor and several of its Coining Presses

An individual planchet is maneuvered in between obverse and reverse dies (see how dies are made). The hammer die (the obverse) is pressed at incredible speeds towards the anvil die, stamping both designs into a planchet and officially turning it into a coin. This all occurs in the blink of an eye with up to 12 coins struck each second.

Inside Coining Press, Denver Mint (a)

The main, internal area of a Coining Press

Inside Coining Press, Denver Mint (b)

The “pressing” area of another Coining Press

This video shows exactly how fast the presses work. This one is striking quarters.

 

After pressing, the coins drop into a catch box to await manual inspection. This video shows a catch box on a Coining Press for Lincoln cents.

 

One coin in the catch box from each production run is checked for flaws before the batch is let loose for packaging. If the coin has an error, the entire lot is scrapped. They end up in a waffle machine, which destroys their designs.

Waffles, Denver Mint

These waffles were once coins.

If the coin passes inspection, the press operator pulls the trap on the catch box and the coins fall onto a conveyor and travel to a packaging room.

 

Counting Coins and Bagging at Denver Mint

All freshly minted circulation quality coins are then automatically counted and placed into massive bulk bags which can weigh over a ton and require a pallet of their own.

Mitch Salzman, Denver Mint

Mitch Salzman operates a count and bag machine. Fed from the automatic cent line through a conveyor, coins are dumped into the tops of the counting machines where sturdy bags are automatically filled with coins.


Coin Bagging Station at Denver Mint

It takes about 23 minutes to fill a bag. Filled bags can weigh between 2206-2677 lbs. and are moved with forklifts once filled.

Two videos follow. One shows a couple of the coin counters at the Denver Mint and the other shows a line of counters, starting at the bottom and working back toward the top.

 

 

Bulk bags go into storage in the vault, but generally not for long.

Racks of Bulk South Dakota Quarter Bags (1), Denver Mint

Racks of bulk bags with quarters

Racks of Bulk South Dakota Quarter Bags (2), Denver Mint

Racks of bulk bags with quarters

Racks of Bulk South Dakota Quarter Bags (3), Denver Mint

Racks of bulk bags with quarters

Racks of Bulk South Dakota Quarter Bags (4), Denver Mint

Racks of bulk bags with quarters

The next stop is the loading docks, which is where the process all started. What came in as rolls of metal now goes out as coins (and scrap). The coins continue the journey via trucks to Federal Reserve Banks and eventually end up in your pocket.

Next Article in Series About the Denver Mint

Thank you for stopping by! Please return Monday, Jan. 20, 2014, for the next article in our several part series about the United States Mint at Denver. It’ll focus on the packaging of numismatic sets and include more photos and videos. To catch up on all of the articles, there are links to them in the upper right column.

{ 1 comment… read it below or add one }

bijan azimi July 7, 2015 at 7:41 pm

hello, i wonder how a sheet of coil is made after being outsourced by the us mint. is the composition of copper and nickel mixed at one time or is the copper coil gets coated by nickel? thanx.

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