Riv Nuts holding hinges to trunk lid keep falling out

[Dodgeman]

I am having problems getting the riv nuts to hold the hinge bracket to the fiberglass trunk lid, They continue to pull out when I put a little pressure on them while tightening the 1/4-20 hex head bolts.
The slightest pressure caused them to tear out.
Have anyone had this problem and what did you do to fix it.
Thinking of bolting thru the lid.
I would add photos but don't know how to.

Thanks,
Bob

[NAZ]

https://www.mcmaster.com/97217a393

Use rivet nuts made for plastics such as the ones at the end of the link above. Those ones that come in the kit are not designed to hold in soft materials like fiberglass.

[Kamp]

I had the same issue and ended up buying some longer grip rivet nuts and using a longer handled puller.

[Brave Salmon]

after screwing up several, I opted to make up little plates of 080 aluminum that matched the contour of that area where the hinges go. Then I used flat head 8-32 screws through the fiberglass and into the molded backing plate. Drilled, tapped, and counter-sunk flush of course. Then I drilled new holes for the rivet nuts through my plate and installed the rivet nuts. Holds great, is nearly invisible after paint and will last a long time. Goo luck.

[michael everson]

It looks like those Rivnuts are crushing above the fiberglass rather than sandwiching it. They might be too short. What tool are you using?
Mike

[Garage Guy]

That was my thought also, I do not see any space between the flanges of the Riv nut or any fiber glass remnants or residue left in between were you would expect to see some.

[peterh226]

Maybe the hole for the rivnut was a bit too large. It needs to be a tight fit.

[GoDadGo]

https://www.mcmaster.com/97217a393

Use rivet nuts made for plastics such as the ones at the end of the link above. Those ones that come in the kit are not designed to hold in soft materials like fiberglass.

Man You Know Some Stuff & Most Of It Is Darn Good!
I'll keep this en-grained in my excrement filled brain.

[NAZ]

Thanks Steve.

Guys, it's good you're analyzing failures and if you carry that further you'll see that the standard rivet nut that works great in sheet metal is not such a great design for softer materials. If you've ever worked with drywall anchors you'll be familiar with the type that have expanding pedals that open up against the blind side of the drywall to make a much larger footprint and better resists pulling through that very soft material. The link I provided in post #2 to the rivet nut designed fr plastics is a similar design. I even use these on O temper thin aluminum to give greater resistance to pull-out. And if you can access the back side, use these with flat washers or fender washers for the ultimate pull-out resistance.

Here's a link to a video demonstrating how expanding pedal rivets can help solve pull-out issues in thin soft materials. A rivet nut works on the same principal as a rivet.

https://www.youtube.com/watch?v=kccZ92x4bMA

[peterh226]

I ordered these and I'll be using them in several spots I expect! Good idea.

[HVACMAN]

NAZ always has good advice. I used these on the trans tunnel and a few other places. If these pull out you need to relax and back off the torque wrench a little. lol