Lubricant for plastic on metal


I have some cheap electrical pushbutton switches that are showing
signs of wear on the plastic moving part. Also, plastic "dust" is
fouling the contacts. Would heavy lithium grease, mainly because I
have lots of it already, be a good candidate here after cleaning?
Also read this while Googling;
"I think this is an area of rapidly diminishing returns. The
difference
between a good lubricant, a better lubricant, and the best lubricant
is
trivial compared to the differences between lubricated and
unlubricated"
Reply to
oparr
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The cheap styrene buttons rubbing on a poorly machined switch barrel are the problem. Lubrication does little good when there are burrs and other defects scraping the moving parts.
Were I to make one from scratch, the barrel would be reamed, and the buttons made of polypropylene or HDPE.
LLoyd
Reply to
Lloyd E. Sponenburgh
I'd use spray silicone lube. Grease will just attract dirt.
Karl
Reply to
Karl Townsend
Silicone spray is what i'd be using.
Reply to
RBnDFW
Actually, that's not the problem in this case. It's a push-to-make, push-to-break switch. The moving contact is a thin metal washer, literally, with a plastic rod through its center. The washer is shaving the rod as it moves and the wear pattern is obvious. Granted, I'm purposely subjecting it to over 100 operations per day, far in excess of normal usage.
Reply to
oparr
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And that would be because the hole in the washer was cleanly de-burred, edges rounded, and sidewalls polished -- or not?
My underlying point was that cheap switches are cheaply made.
Buy some good escapement-operated push-push switches, and they'll last hundreds of thousands of operations.
LLoyd
Reply to
Lloyd E. Sponenburgh
Not really, it's cleanly deburred, however, the washer being so thin and the arrangement only centered axially by two springs, it wobbles, allowing the washer to "whittle" the rod while operating.
That's at least 54 years at 5 operations per day. Overkill for the purpose.
Reply to
oparr
Thanks guys.
Reply to
oparr
If the edge of the washer is thin enough or sharp enough that it's scraping away the plastic, it'll also do a good job of removing the lube. I'd expect grease to last somewhat longer than silicone in this situation.
Reply to
Ned Simmons
Me too. I may just subject one of them to 10,000 operations using the Z axis of a CNC machine. Heck, something else in the switch may give before the plastic rod.
Reply to
oparr
[about a switch with a wear issue]
Overkill kills the problem. Then the problem stays dead. Overkill is good.
Mass-produced microswitch mechanisms are inexpensive and very durable, and available with LOTS of actuator choices. Buy some, or get 'em from scrap equipment (every dead microwave oven has two nice microswitches in the interlock system).
Reply to
whit3rd
Overkill makes no economic sense in my case. I'm currently testing the switch, with lithium grease applied, for 10,000 operations on a CNC machine. I'm good if it survives that. Thanks!
Reply to
oparr
Some kind of metal sleeve around the plastic rod? Or, sand the metal washer hole, to make it smoother.
Reply to
Stormin Mormon
I have 175 of these switches to correct. Just adding grease (a 2 minute exercise) was sufficient to allow for 10,000 operations without any signs of wear or falling apart. A day vs night comparison to just 800 operations without the grease. Already have the grease, bought it around 14 years ago.
Sometimes, dirt cheap, made in China, needs a helping hand.
Reply to
oparr
I missed the moment where you wrote that you had a LOT of switches to correct. In that case, the dab of grease makes more sense. Thanks for letting us know how it worked out.
Reply to
Stormin Mormon
I like the outside-of-the-box use of CNC. Clever.
Reply to
Bob Engelhardt

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