Electrical Contact Material



The PROPER method to clean an electrical contact (pair) *that is meant to be serviceable*, is by a process known as "burnishing". The tool is a flat strip of thin metal with a face surface texture of about 3600 grit. Short of having such an easily obtainable tool, the best and second and ONLY other proper method is the "paper" suggestion, but I would choose something a little stiffer than paper towel, also exhibiting far less fiber. So, I would use matchbook thickness or business card thickness media. A business card, in fact, is a good, if not excellent choice. Not an enameled version though. The paper is a refined wood fiber pulp media that has the perfect mild abrasion qualities required for the task. A true abrasive cloth is not proper, and is meant for other applications. If the contact faces have become pitted or damaged from an arcing/ current inrush event, you will likely not be able to get the original face shape back. If it is your lawn mower "points", you replace them, though I have made several keep on tickin'. Those WOULD require at least one of the contacts be abraded.
For normal every day use though, you should never have to worry about it, because any contact(pair) made from a proper media will be one of those we (science) knows to be of a low oxidation factor, or of one where it matters not. I believe, and only from _some_ experience, so not expert, that Platinum is most common in small scale applications, Gold is second, and most common due to modern electroplating and alloys of gold being able to be referred to as Gold, another is Silver, often used for RF where refined HV arcs would be encountered and oxidation layers are OK.
Use the paper. Non conductive AND high Volt per mil isolation? Use transformer paper. Top brand is "Nomex". Made by DuPont many decades ago, and barely matched (others exist). Something on the order of 1500 Volts per mil, IIRC, though I would recommend at least 5 or 10 mil media to acquire the stiffness to push as well as pull on it while clasped by the "contacts". 15 mil even better.
Have a nice day...
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Back in the days of punched cards, field service engineers would often use an (unpunched) card for this purpose. It was just the right abrasiveness and stiffness for cleaning many things including contact surfaces and disk head surfaces of that time. Cards were cleaned of loose dust during manufacture to prevent dust shedding into card punches and readers. They were also made of paper which doesn't soften if it gets wet, so you could if necessary use water or a solvent on them too, whilst still staying abrasive and without going soggy (although they were mostly used dry).
Paper tape had the same properties, but was thinner, and finer level of abrasiveness.
--
Andrew Gabriel
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On Sun, 16 Jan 2011 08:41:08 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

--
Unfortunately, most, if not all, (as I recall) paper tape was oiled in
order to increase the life of the punches, so wasn't really a good
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Andrew Gabriel:

But also to clean the build-up of magnetic material on floppy disc readers' heads.
Do anybody here use a pencil (or even, for thick oxydations, pen) eraser to clean contacts?
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F. Bertolazzi wrote:

When I was an amusement machine repairmen, the company issued a thing that the boss called a "fiberglass eraser" for cleaning edge connector contacts.
It was just a bundle of stiff glass fibers in a plastic tube with a screw to extend the bundle of fibers as they wore down, and it worked a treat!
It didn't leave any rubber residue like a pencil eraser might have.
Cheers! Rich
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On Sun, 16 Jan 2011 16:31:42 +0100, "F. Bertolazzi"

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Real life horror story:

Once upon a time, in a previous life, I used to design oceanographic
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John Fields:

Now I understand why you had to deal with drydocks. Usually those places are populated with retarded monkeys, you did not seem to fit wery well there (apart from the fact that you're an asshole. Now we're even, peace).
I've been on board one of those "oceanographic" vessels. Their base in the west Mediterranean is in La Spezia, 100 km from here.

Yeah, sure, nothing to deal with russian submarines. ;-)

A couple of weeks ago I "repaired" a friend's "boom box" the same way.
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Our field service staff had a sort of glass fiber propelling pencil for that. It was like a very thick propelling pencil, but instead of pencil lead, it had a dense mass of fine glass fibers, which wore down over time.
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Andrew Gabriel
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Andrew Gabriel:

Yes, it's an eraser for china ink used by achitects on tracing paper. Very effective. Maybe too much.
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wrote:

When I was a lad we used erasers to clean the power rails of our slot car track.
George H.
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F. Bertolazzi Inscribed thus:

Yes ! I've used pencil erasers to clean fingering on PCB contacts.
--
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Baron.
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Nunya Inscribed thus:

The type of paper towel that I referred to and have used many times is the hard folded ones, about a foot square and usually found in factory washrooms. They have a hard lint free surface which makes the material suitable for this purpose. I've also used the hard toilet sheets, the ones with a smooth surface on one side, for small contact points with good results.

I would suggest that the type of contacts (points) that you refer to are the only type that a contact burnishing file should be used on. I recall that in the old "Kettering Ignition" days, a suitable "Contact File" was always a must have toolbox item. As was a spare points set and condenser !

--
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As I mentioned, outside of data lines, voltages will be small(-5V, +5V, +12V, +24V). And there will be no arcing anyway, because there will be no current during either make or break. And though not air tight, this will be an enclosed project. So paper will not do, because I'm looking for something permanent. A stiff wiping material to put inside the enclosure.
Thanks.
Darren Harris Staten Island, New York.
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On Sat, 15 Jan 2011 16:55:13 -0800 (PST), Searcher7

--
Sounds to me like you're dreaming up a mechanical nightmare, what with
having to put the paper in there, do a little wiping, and then remove
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John Fields Inscribed thus:

Certain types of gaming machines use a stack of rotating disks of SRBP material, similar construction to a HDD platter stack, with phosphor bronze contact strips and sterling silver studs to determine payout values. The contact strips when not in contact with the studs are in continuous contact with the SRBP disk. Surprisingly over a long period of time grooves are formed in the SRBP disk surface. Since there is 240v 50Hz present on the contact studs, debris from the continual friction can cause arcing and breakdown of the SRBP material. The point being is that these things run reliably for years without maintenance.
--
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It's not at all clear what the OP is trying to do. Seems like a little gold flash over his phosphur bronze might get rid of the oxide issue?
George H.
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It would appear the OP does not really know what he wants, cannot explain it, and it "rolls" each time he learns a little more about what he wants by reading posts.
It's not at all clear what the OP is trying to do. Seems like a little gold flash over his phosphur bronze might get rid of the oxide issue?
George H.
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Even with gold there is still the issue of having to clean the contacts.
P.S.: I don't know if anyone else has this issue, but Google Groups will not let me post in another thread here that I started called. Making cables". I've attempting to post a response for the last three days. Has anyone else had a problem like this?
Thanks.
Darren Harris Staten Island, New York.
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On Sun, 16 Jan 2011 15:32:41 -0800 (PST), Searcher7

--
Google groups, as far as USENET is concerned, is nothing more than a
web based SPAM outlet looking for revenue, and bites.
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Searcher7 wrote:

WHAT THE FUCK ARE YOU TRYING TO ACCOMPLISH? People have been doing this stuff for decades! What's impelling you to reject every reasonable answer you've gotten? Are you on a secret mission from an alien planet or what?
Or are you just another damned troll?
Thanks, Rich
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