What is the best method to repair stripped threads in plastic?

[Old2stroke]

Good grade of epoxy in the hole and the screw wrapped with teflon tape for a release agent works. If you are into fiberglass/epoxy work and have any chopped fiberglass filler to add to the epoxy, it will greatly enhance it's strength and prevent cracking in the hole.

 

[ham]

Good grade of epoxy in the hole and the screw wrapped with teflon tape for a release agent works. If you are into fiberglass/epoxy work and have any chopped fiberglass filler to add to the epoxy, it will greatly enhance it's strength and prevent cracking in the hole.

Years ago we used to mix baking soda and crazy glue to make a super hard "plastic" for repairs

 

[ham]

Lot of people don't know before you screw those screws used in plastic downward, you should turn the screw outward to allow it to drop in the original threads otherwise they easily catch the side of the hole and rethread or tap another thread inside the originals. <snipped>

My grandfather practically beat this into me when I was a kid, I do this with all bolts/screws. It's shocking to me how few people know about this. Even metal threaded holes etc doesn't matter, still should back them out a turn until they drop into place. It hurts me to watch guys on youtube that use impact drivers to just blast bolts in

 

[67L36Driver]

The plastic on the 029 types is hard enuf that your everyday Helicoil thread insert can be installed if there is enuf meat around the hole.

Results are stronger than original. [emoji108]

 

[edisto]

I ended up finding these. Heat set threaded inserts. It’s overkill for my particular situation but am going to go ahead and epoxy in a few in the interest of “doing it right”

If I was going to do it right, I'd put in a Helicoil...those look like they take up a lot of space.

 

[anlrolfe]

This stuff looks like JB weld.

 

[huskihl]

I melt trimmer line into the hole and use a heated pick to melt into the existing plastic so it all bonds together. Then drill a new hole. Good as new

 

[ham]

This stuff looks like JB weld.

I actually already have one of these kits and it’s adamant that it cannot be used for plastic. I think it heats and expands when curing.

 

[r black]

airless plastic welder fill holes in and retap :


Airless Plastic Welder Kit makes easy plastic repairs on virtually any of your vehicle's plastic parts Make quick, durable repairs on plastic bumpers, grills, any plastic car part. Welder heats the thermoset polyurethane welding rod as you feed it through, melting it into the cracked plastic (see "Video" tab).

• Includes welding rods for polyurethane, polypropylene, ABS, TPO, polyethylene, nylon, polycarbonate
• Also includes FiberFlex Flat Repair Stick
• 1-year manufacturer’s limited warranty
• Airless plastic welder kit repairs virtually any automotive plastic. It’s perfect for fixing plastic bumpers, grills, and more. Complete kit will make it a quick, easy task. 1-year mfr's. limited warranty.
• Includes welder, six 15' welding rods (one each: polyurethane, polypropylene, ABS, polyethylene, TPO, nylon), one 4' length of polycarbonate welding rod, one 15' length of FiberFlex flat repair stick, wire brush, temperature control unit, carry case and detailed instructions.
  Make quick, durable repairs on plastic bumpers, grills, any plastic
• AIRLESS PLASTIC WELDER MODEL 7

 

[anlrolfe]

I actually already have one of these kits and it’s adamant that it cannot be used for plastic. I think it heats and expands when curing.

Ooff...
There's got to be something similar for plastic. Maybe not packaged as a kit but if you can find a reliable epoxy that's the important part. The release agent may be had seperate. I see this far better than wrapping threads with teflon tape and getting a hole not much better fit then the reamed out, stripped hole you started with.
So far I like the idea of :
1) DIY hot melt string trimmer line swirled into the hole or
2) Two part epoxy, drill and tap