Revisit Plexi fasteners

Bill Musarra · 05-02-08, 07:16 PM

I have done a search for the type fasteners guys are using on their Plexiglas. It seems every one has a different approach, from button head ss with washers to the plastic screws. Mine came with steel flat head(V) approximately 8-32 self tapping screws. I want to change it around. I was at our local Giant Ace Hardware store and came across these pictured below. After searching and reading, I think there needs to be some sort of mechanism in the fiberglass to hold the screw down. Each of these is different. Some brass, some steel.The brass ones were designed to be used in plastic. They are knurled and would probably be best if a bonding agent were incorporated in its install. They are installed with a flat blade screw driver or allen wrench. I plan to use the nylon off white screws with a blacked out edge at the mating surface. I will use a thin foamed gasket material to help seal the plexi a little better to the door and rear clip and help in keeping the paint from chipping. If a rivnut is used, there will be a flange that protrudes above the surface and will leave a gap and increase the likelyhood of chipping the black paint. I don't plan to drive in the rain, so leaking isn't an issue.
Some have advocated helicoils, but they are too expensive for me. I think the brass type insert here is as good and only runs about $24 per 100 vs. 4-6$ for 5-10 or so helicoils. Plus you have to buy the install tool.
I am looking for the choices members have chosen for attaching their Plexiglas.

Bill

Tim Kay · 05-02-08, 08:10 PM

I've had good luck with aluminum Rivet Nut Inserts. They mount flush and hold fairly tight in fiberglass although I have a one or two loosen up but more to do with sloppy hole drilling. Can be purchased thru McMaster-Carr catalog page number 3215.

MReid · 05-02-08, 09:16 PM

I used brass wood inserts from mcmaster.com with a wide head ss screw:

They are threaded and can be screwed into the fiberglass. I bonded them in with epoxy, sanded the heads off flush with the body, and when I finished the panel prior to paint they only show a very small threaded hole:

Mark Clapp · 05-02-08, 11:50 PM

Bill, to save money on any of this hardware, check with a fastener supply house like Fastenal. The 6/32 ss screws I used were 10 cents each or more at the hardware store. I got a box of them from Fastenal for $1 for 100 screws so 1 cent each. I'll bet they sell the heli coils in bulk like that too. My heli coils have held great for eight years now, mounted to just below the surface so invisible, and required no glue to stay in place all this time.