[GreenKeys] Fwd: Filing Contacts - Don't

[Bruce Gentry]

As a veteran of decades in the elevator craft, cleaning contacts is best 
approached as "It depends". Relay contacts designed for millivolt level 
signals often have gold plating. It is frightengly thin, and clean paper 
with a little solvent will get the schmutz off without destroying the 
plating. Contacts carrying signals and current at intermediate levels, 
up to about ten amps, can be cleaned with a burnishing tool, preferably 
diamond. Take it easy, don't take off too much metal and flush the 
cleaned surfaces with solvent if you can. For heavy currents, ten amps 
and up, the contacts are usually a silver/cadmium alloy. Use a diamond 
or steel burnisher. Unless they are really big, don'try to file out the 
craters. just level the spikes, removing as little metal as you can 
while getting the job done. It's normally wise to flush the contacts 
witha spritz of solvent. Don't use sandpaper or emory cloth, they embed 
abrasive crystals in the contact surfaces and can be worse than doing 
nothing at all.

    Bruce Gentry, KA2IVY

On 1/16/23 12:23, Tom Hunter wrote:
> Andy,
>
> Filing contacts is likely to take off a thin coating contact of 
> contact material.
>
> I use strips of card stock pulled between contacts as I hold them 
> together. They will will come out with a black stripe.
> I usually dampen the strips with alcohol at first. Then I pull dry 
> strips through until they come out clean. I will
> go through many strips. Paper is cheaper than new contacts!
>
> If you have been filing contacts you may already have ruined them and 
> they will need to be replaced.
>
>
> Tom   N3CRK
>
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