This paper is aimed mainly at the small to medium-sized jewelry manufacturing operations interested in working with platinum group metals.

Preparing the Melt
It is important to start with pure metals.  It is preferable to use platinum in plate or shot form.  There are several methods to adding alloying element, but our preferred method is to prepare a foil of pure platinum and fold it into a pouch large enough to hold all the powdered iridium or ruthenium.  The advantage of this method is that the melting platinum will immediately soak up all the powdered alloy material, thus diminishing loss created by the torch blowing away metal powder.

The Melting Process
The crucibles used are Wesco 2H or 3H platinum melting crucibles.  The equipment we use is a torch with a 12-inch neck and a single-port tip.  As fuel we are using an oxygen/propane mixture.   The crucible is placed on a 6"x6"x1" piece of ATJ grade graphite.  This should be placed on a nonflammable substrate such as ceramic or refractory brick.

 Melt the platinum at about 35 pounds of propane pressure and about 65 pounds of oxygen pressure.  As the platinum starts to melt, the alloy mass will be floating in the crucible like ice in water.  The molten mass should be swirled with the force of the flame.  Continue melting until the alloy is completely dissolved.  The melt should be allowed to cool until all the color is gone.  A gentle tap will make it fall out of the crucible.

The Forging Process
At the onset of the forging process, the platinum button is picked up with a pair of tongs and hammered square.  It is then returned to the graphite square for swedging. The white-hot button is then hammered again on all six sides and the swedging process is repeated.  This button, now rectangular in shape, is hammered for a third time.  At this time the forging can continue if a square rod is desired.  Do not swedge without hammering after swedging.

Rolling
If the forging has been done properly, the rectangular ingot or square rod can be rolled down to any thickness without cracking.  Annealing should take place after every 50% reduction.  For making round wire, the rod should be rolled to the thickness of the diameter of your largest die, then coiled and annealed on the aforementioned graphite square.  It can then be passed through successive dies with about 0.005 diminishing sizes, without further annealing.  Beeswax is the recommended lubricant for the drawplate.

For small quantities of jewelry findings, a hand held torch is sufficient for annealing.  A smaller flame than for melting is recommended, so that one does not inadvertently melt the platinum.  The platinum should be annealed to a bright orange and held for about 15-60 seconds, depending on the quantity.

Stamping
Stamping operations can be divided into two types of processes.  The first is blanking.  In this method, the metal can remain hard or half-hard rolled.  This produces clean edges with very little burr.  The second type of operation is where the previously blanked piece is further shaped by one or more strikes in a forming die.  The blank can be deformed into shapes which will require trimming operations in trimming dies.  Continued annealing is recommended during these forming steps although some simple shapes can be blanked and formed in one operation.

Machining
When one talks about machining of platinum products, one is usually discussing lathe turning, milling and drilling.  In lathe turning, the product is spinning around, as the tool is stationary.  In the milling and drilling process, the product is stationary and the tools are turning.  These methods are well known from machining gold, but the difference lies in the type of tools used, the lubricant and speed of production, when it comes to platinum.

V3N2

Platinum Fabricating and Stamping
Georde C. Lambros
Precimet Corporation

This is an abbreviated version of the original work. For full technical details, please consult the original paper.