Question- DMM grease

[MikeO]

"Silicone Contamination

[snip]

We've got to be a bit careful here not to slip into homeopathic engineering.  Silicone is the ultimate contaminant, because it creeps.  Everything, and I mean everything, is silicone contaminated.  Clean rooms are silicone contaminated.  Write to the NASA engineers (by the way, they do write back) and they will tell you, the single largest contaminant on the space shuttle was always silicone.

Silicone, the oil, is not an issue.  If it converts to Silicon carbide, that is the issue.  I'll check in with a chemist (my wife) but, I think in order to make that conversion, you are going to need a lot of heat: an arc.  The issue would be that the silicon carbide crystals would exist bonded to the contact, and being an abrasive, shorten the life of the contact, and further, being an insulator, increase the resistance of the contact.  That would be a spiral, as the effective area of the contact would reduce, increasing the temperature of the contact, further shortening its life.

Without the arc, we aren't getting there.  So, manufacturing relays?  Maybe not silicone grease.  Low current switch?  I'm just not yet ready to stop what I've been doing successfully for years: putting a healthy dab of silicone grease in there.

How did we get here?  Was it a DMM rotary switch?  I've got to review the thread.  I've seen a worn out DMM switch once.  Really, just once.  I recall what bench it was and the RIIIIPPP sound it made every time that tech spun it.  He didn't have a gentle touch.  Bright guy, easy to work with, pretty talented, but tough on the gear.  When we had something repaired, it usually came from his bench.  None of his meters had screws in them: he liked a fast battery change.  His keyboard used to bounce of the desk when he typed, and we kept the spare keyboards and mice in his cube, as he seemed to have the most bad luck with them.

I say, great work on this one all, but I think we've taken it far enough (for me, anyway).  When I rebuilt the motor on my wife's sewing machine (my great grandmother's last machine), I used silicone grease.  Now I know: that was an error.  If I find occasion to take it apart again, I'll clean it out.  If it fails first, a little wire brush on a dremel should clean that right up.  If I tear down one of my meters, it is definitely getting a dab of silicone grease!  I work around salt water though, and I'll take the risk of silicon carbide crystal formation over the guaranteed alternate: corroded contacts in short order.

Regards,
Mike O'