Anything like a PEM nut that I could fit *into* a sheet of lexan -- without worrying about torsional forces cracking the lexan or working the PEM nut out of place?
- posted
7 years ago
Anything like a PEM nut that I could fit *into* a sheet of lexan -- without worrying about torsional forces cracking the lexan or working the PEM nut out of place?
IIRC "helicoil insert" might help. Of course there's nothing that is free of stresses, particularly with temperature swings.
Here is a selection guide for threaded inserts for plastic. Lexan is polycarbonate, PC in the chart.
----- Regards, Carl Ijames
How about a "toothless" T-nut...
...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et |
Check TAP Plastics they may have something. They sell display cases and such.
-- Chisolm Republic of Texas
On Fri, 27 May 2016 18:51:08 -0700, Don Y Gave us:
Lexan is elastic.
Are you sure that you do not simply have cheap home depot polycarbonate, which is brittle?
Also, HEAT IT UP first, THEN apply the FROZEN PEM
I banned my MEs from using PEM in anything. Only T and nut plates were allowed. Manufacturing never got PEM installation right and they would pull out etc. All problems ceased!
Lexan (polycarbonate plastic) is rubbery. That makes it hard to drill accurately (which is required, for a metal-insert fit), and makes it not retain a knurled barrel very well, and deforms the plastic surface near any such stress-inducer.
A bit of adhesive and a T nut may suit you; if you dislike loose metal bits, I'm sure some kind of polymer T nut could be designed and built to order.
Captive nuts (sheet-metal-tooth things that snap over an edge, aligned with a clearance hole) are widely available, and don't come loose.
Captive nuts => Tinnerman nuts ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et |
I had in mind the clip-in-place kind,
which, like inserts, join to the material and aren't separate loose hardware.
Another option, now that I think of it, is the expanding-barrel Riv-Nut sort of thing
Generally called Tinnerman nuts...
"Expanding" may crack the base plastic.
When the house was built I asked the installer about drilling the shower material. He said to make the hole over-size so that thermal expansion doesn't crack the shower walls. ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et |
On Sun, 29 May 2016 11:05:59 -0700 (PDT), whit3rd Gave us:
And while they work fine on SHEET metal, would likely not work very well at all in this application.
Not likely in polycarbonate; it's rubbery, not brittle. Some of the catalog items are recommended for plastic.
I've had some luck using inserts like these:
...when I under-size the hole, then use a soldering iron to heat the brass insert so it sort of melts into the lexan. I would actually just place the insert onto the iron then use the iron to press it into the plastic. Neve r had a problem with them coming free, spinning, or cracking the plastic. Precision alignment, however, was an issue.
I think that the way they are so neatly put into plastic sheets, is via an ultrasonic press.
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