broken thread in grp

[john]

i've just overtightened a threaded bolt holding the saloon table and ruined the threads in the GRP it's tapped into. The bolt is three inches long. How can I make this good and be able to tighten it up again? I had thought of using epoxy in the hole - would this work? any suggestions gratefully recieved - I can't go sailing until it's fixed!

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[snowleopard]

you can use epoxy thickened slightly with e.g. microfibres. very lightly lubricate the bolt and insert while the resin is wet. you'll then stand a fair chance of unscrewing it at a later date

alternatively you could tap the hole out to the next larger size.

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[Paulka]

Providing there is still enough material around, I would drill the existing hole to a wider diameter, and use a common plastic anchor. Its amazing how strong those things are!

Other possibility : chemical anchor.

Have a look there :

http://www.hilti.com/holcom/modules/prcat/prca_navigation.jsp?OID=-9255

Hurry, and go sailing!

Good luck.

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[vyv_cox]

Put a Helicoil in. See <A target="_blank" HREF=http://www.kevinmosshelicoiling.co.uk/services.htm>http://www.kevinmosshelicoiling.co.uk/services.htm</A> for simple instructions in doing it. They can usually be bought at automotive factors, engineering suppliers and similar outlets. You may be able to hire the special taps, so perhaps a tool hire shop.

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[Evadne]

That is what I would try, although I have a feeling that helicoils are made of spring steel, which rusts.

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[vyv_cox]

Stainless in my experience. Even if carbon steel it seems unlikely to be a problem in this duty.

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[dieselhead]

epoxy it in.

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[Avocet]

Depending on how much "meat" you have left round the hole, you might be able to get an engineering firm to make you a stainless or brass (or whatever the bolt is made out of) bush with a matching female thread and a coarse knurl or some groovs on the outside. If you then drill out a larger hole on the GRP and bond the bush into it with some thickened epoxy you'd probably get a very good and permanent repair.

Failing that, I think Screwfix sell some sort of resin in a dispenser that's designed to be injected into masonry walls to hold threaded studding for fastening things to.

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