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Peter W. Rowe[_2_] February 16th 13 07:47 PM

Estimating gold content of "probe pins"
On , in Ignoramus21620

At this point I am not sure what auction it is from, but I was digging
through my "get to one day pile" and accidentally found a couple of
lbs of gold plated industrial probe pins:

I decided to estimate gold content.

I looked up online and found that the best gold plating is 50
microinches. So, I assumed that thickness, as these are very expensive
industrial pins.

The expense of industrial parts more often relates to precision. Gold plating
is seldom an ideal process, since points, edges, tend to get thicker plating,
and hollows get less, reducing the precision of parts. Gold plating will be put
on according to engineering needs, and thicker is normally needed only when
resistance to wear, or corrosion, is needed. I doubt either is the case here.
I'd assume here it would be like the gold plated connectors on circuit boards,
there to prevent minor corrosion/oxidation, and to enhance the electrical
conductivity. This normally doesn't need thick plating, but exact thicknesses
is something I cannot guess at.

50 microinches is appx. 0.001 millimeter.

I further assumed that the pins are 0.1mm thick wall (they are hollow
tubes inside, they are spring loaded).

So, on a 0.01mm material, there is two layers (inner and outer) of
0.001mm gold plating.

..01 mm is really really thin wall material. I'd bet your tubes are at least
slightly thicker, since they need to resist mechanical deformation. Remember
that these, for electrical conductivity, are likely to be non-ferrous metal, so
not as strong as some things might be. But again, I'm guessing. Also, I
seriously doubt that there is any gold on the interior of the tube. Getting it
there would pretty much require either a process other than electroplating, or
would need plating to be done before the stock was made into tube. Unlikely.
Getting gold to plate evenly into the interior of simple depressions is alreay
hard. Getting to the interior of something deep, like tube, pretty much
requires an anode in the plating process to be inside the tube. Unlikely. And
most likely, not needed. So assume plating only on exterior surfaces where you
can see it..

That is 0.002mm, or 2% by volume.

Since gold is 3x heavier than other metals commonly used for those
pins, like iron and nickel, then the gold content is 6% by weight.

I would expect either a copper or copper/nickel alloy...

For 2 lbs of pins, they could contain 1.92 oz of gold.

Am I way off here?


Could, of course, is an open term. Likely? I doubt it. Compare this to gold
plated costume jewelry. For several pounds of typical scrap electroplated
costume jewelry, one might expect refining returns on the order of a gram or
two per pound. But again, it varies widely.

May I suggest that you post this question a well, to the "Orchid" mail list
forum hosted on That web site, set up as a service to jewelry
makers and metal arts workers, is one of the busiest discussion forums on the
subject on the net, and the mail list, by far the largest such forum, far busier
than this newsgroup ever was, even when it was active, which it now is not. The
Orchid list (which is not about flowers. It's about jewelry related topics.
It's named "Orchid" because it's owner is in Bangkok, where there are Orchid
flowers everywhere...) currently has something like 12 thousand active
subscribers. Post your question to that list, perhaps asking for off list
direct replies so you can find them without needing to read the list, and you
are guaranteed to have reached a fair number of professionals in precisely the
fields you need to reach for your answers, ie refiners and scrap metal dealers
who've dealt with various forms of industrial gold plated scrap metal before.


Peter Rowe
(still, though not every day anymore since now there's seldom any activity) newsgroup

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