Bonding metal thread into plastic

[laika]

Simple, stupid question I'm worrying far too much about but I'd rather learn a bit about boat materials science than bodge a solution.

My whitlock pedestal throttle pod (subject of a recent thread) is held together by 4 bolts which screw into threaded metal inserts bonded into the plastic of the pod. One of these came out attached to the end of one of the bolts. Easy enough to get off the bolt but what's the "right" way to put it back? I have some magic glue from a man at a boat show one year which would doubtless work but it looks to have originally been secured with some kind of cement. Having never owned a brick I'm not familiar with cement.

What adhesive should be used and what is a threaded cylindrical insert that a bold screws into called anyway (obviously not an interscrew or nut)?

 

[prv]

I'm not sure there's a better generic name than "threaded insert". There are helicoils, used for replacing damaged threads usually in metal, but they have both an internal and external thread and the latter cuts into the walls of the hole rather than being bonded in.

I'd probably use epoxy to glue it back in. That might even be what your "magic glue" is.

Pete

 

[macd]

I'm not sure there's a better generic name than "threaded insert". There are helicoils, used for replacing damaged threads usually in metal

If I may, Pete, there are thread inserts, one brand of which is Helicoil. Other brands are available...
Very useful on boats since they're usually stainless, so any corrosion takes place between thread and surrounding metal, rather than between thread and fastener. (Many of the larger fasteners on our Selden mast engage on inserts as standard, at least partly for this reason.)

But I digress. Nothing's likely to stick well to the OP's plastic bits, but as you suggest, epoxy might well offer some mechanical bond.

 

[laika]

Indeed epoxy is the answer to most bonding solutions (although I recently finished my big bottle) but I was intrigued by the fact that this thread thingy was originally bonded in with what looks like cement: an adhesive which I have no previous experience of. Yes yes I know that sounds stupid but I refer you to the previous "never owned a brick" statement...

 

[prv]

It may have looked like cement, but it seems pretty unlikely to me that it actually was cement (as in masonry mortar, vs some kinds of unrelated glue referred to as "cement").

Pete

 

[jwilson]

Similar setup on my Jeanneau with the GRP binnacle instrument cover: four original pressed-in thread inserts rusted and came loose: replaced with S/S nuts glued in to the inside with blobs of epoxy putty (avoiding clogging the threads). No further trouble.

 

[laika]

It may have looked like cement, but it seems pretty unlikely to me that it actually was cement (as in masonry mortar, vs some kinds of unrelated glue referred to as "cement").

Doh! of course. It's doubtless just epoxy with stuff loads of filler. I did say it was a stupid question (now how do I delete this whole thread to save embarrassment....)

 

[anoccasionalyachtsman]

Don't despair! You may be trying to glue something with an awkward plastic, and ordinary epoxy may not do it.

I had to find a glue that was effective on nylon fishing line for an artist. Lots of experimenting later, the best that I found was JB Plastic Weld

http://modelshopleeds.co.uk/catalog...cts_id=16424&gclid=CObrhazd_c8CFfYV0wodRY0B_Q.

The next best was the stuff that comes from a hot glue gun (Stanley, but I expect all the glues over the counter are much the same) results not rigid, but a goodish grip.

I'm not clear on whether you have still got the insert. If not, I'll dig out a name of a very helpful company who'll probably send you one for nothing.

 

[MoodySabre]

The stuff from the boat is presumably Hafficks which is a superglue type of glue but much better than the cheap superglue. It has no filling ability though. Evostick do a Seriously Strong glue that is waterproof. I mended my daughter's showerhead with it a couple of years ago and still fine.

 

[RichardS]

I would recommend the adhesive used to bond Blakes seacocks into Longbows.

Richard

 

[prv]

I would recommend the adhesive used to bond Blakes seacocks into Longbows.

I don't think you can buy "40 years' neglect" in tubes

Pete