No place for precious metals so I am trying here. Does anyone have any tricks or tips on pointing fine (<.002 inch ) 10%PTIR for wire drawing purposes. I have tried aqua regia , NAOH , and mechanical methods. None seemed to be very efficient or safe. Any comments or ideas are much appreciated.
Tech 1

Hi there Tech1,

Long time!
On the assumption that the acronym 10% PTIR stands for an alloy of 90% platinum and 10% iridium, I have moved this over to the Nonferrous Section and made sure it was at the front of the line.

Hopefully somebody will give you an answer to your rather exotic question.

Best regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Here is some information I learned from the H. Cross Company:

"90/10 Platinum/Iridium Physical Properties (Annealed Condition)

Density 21.53 g/cc
Mechanical Properties
Ultimate Tensile Strength 55,100 PSI
Electrical Resistivity 0.000025 ohm-cm
Hardness Brinell 130

The alloy 90/10 platinum iridium, containing 10 per cent iridium, has very good all round manufacturing characteristics: it can be cast, welded, machined and stamped; it is ductile and malleable; can be hardened through working; and does not readily oxidize. Because of these advantages 90/10 Plat Iridium has traditionally been one of the most important jewelry alloys used in the USA, although there has recently been a swing toward alloys of 95/5 Platinum Iridium. Some manufacturers in Germany and Japan also prefer the 95/5 alloy. The 80/20 Plat Iridium alloy is very hard and dense, and is sometimes used in the production of fine wire work."

The melting point of 90/10 platinum iridium alloy is 1800C or 3272F. For comparison, the melting point of copper is 1083C or 1981.4F.

Is the wire already work hardened when you want to point it or is it a lot less ductile than is suggested here?

Best regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

hi ya vettecoupe,
Yup, long time no talk. Still doing the same ole stuff.
Anyway, It really doesn't matter if the PTIR is hard or soft. The size of it ( <.002 ) is the problem for working with. Traditionally, we would use somesort of eletrochemical pointing method with other alloys but the PTIR will not work that way. I have also seen methods of scrapping the wire to make a point but the size of this wire is preventing that as well. There are so many ways of pointing larger wires but the small stuff is always very difficult or there is some silly trick that someone came up with that is usually very efficent and easy. Now, thats what Iam looking for. So, If anyone has some tricks up their sleeve, please pass them on.

Hello Tech1.

Have you tried heating the wire. Since it is fine, take about 12 -18 inches. grip it so that it will not slip out of you fingers, hold the middle of the 12-18 inc piece over a butane torch---same one you might use for brazing wire. When you see the wire start to get red move your hands further apart until the wire breaks. It should have a nice taper to it that ou would be able to stick into the die. Don't heat it too much or you might not be able to grab it and pull it through the die.

Tried the heating method. Not so good. Wire becomes brittle and does not point. Another thing is 12-18 inches of wire becomes very expensive.