On Wed, 17 Oct 2007 17:52:55 -0400, "Ed Huntress"
wrote:


"Jon Danniken" wrote in message
...
Howdy,

I needed some 1/4" bolts for an electrical connection, and as the fastener
store was out of 2" long brass bolts, I was sold something called "silken
bronze." According to the fellow behind the counter, they are 95% copper.

Now that I have them home, I can't find any reference to "silken bronze"
on the web, and would like to know a little more about them, including at
least a torque recommdation.

Anyone know what other name these might be called which would yield some
results?

Thanks for any tips,

Jon

Low-silicon bronze. The guy had a bad accent. d8-)

Electrical properties (I'll let you figure this one out): Electrical
conductivity, volumetric, 12% IACS at 20 deg. C (68 F). Electrical
resistivity, 144 n-ohms-meter at 20 deg. C.

For comparison, here's the grade of copper used for high quality wi
Electrical conductivity, volumetric, annealed, 101% IACS at 20 deg. C (68
F). Electrical resistivity, 17.1 n-ohms-meter at 20 deg. C.

What this means is that the electrical conductivity of silicon bronze sucks.
It has about 1/5 of the conductivity of pure aluminum.

Right - but they're using Silicon Bronze bolts for the other
properties than conductivity - environmental effects corrosion
resistance, dissimilar metal galvanic corrosion resistance, and the
thermal expansion rate of the bolts will be in the same ballpark as
the copper parts they are bolting together.

The current should be flowing directly between the top face of the
pure copper busbar and the bottom face of the copper lug you have
bolted on top. The bronze bolt is just clamping the two surfaces
together, and shouldn't be carrying that much of the current itself.

-- Bruce --