thread repair

[pondy]

rebuilding my race quad for the 2001 season. there are a few threads on the bike that need to be repaired, there are about 5 m6 threads and 2 m10 threaded that are stripped, the m6 hold some fenders on and the others are for the front bumper/grab bar.

i was going to buy a helicoil kit but both kits would come to over £50 and it didnt seem worth it if im only using it a few times, i was thinking of holding an alloy plate on the back of the hole, filling it will mig then drilling and re tapping to the correct size, any problems with this, i have done it before for an m10 hole that holds the brake caliper on, welded, drilled and tapped and holds fine, but this was with a brazing wire

sam

 

[piman]

Hello Sam,

I don't see any problem with that, although recoil kits are very useful to have and last for a long time? The alternative, if there is enough metal, is to go up a size?

Alec

 

[Windy Miller]

Pondy - whereabouts in the UK are you? I think my helicoil kits are the sizes that you need. You are welcome to use them but you will need to buy some inserts, as I have run out! I am in the Medway towns in Kent...

 

[pondy]

am in bury st edmunds. suffolk so not close

the tab is quite small so dont think i could go up the next size, if i did the hole in the plastics would have to be drilled larger aswell, i have to weld some new mounts on the frame to fit another subframe, the threaded holes have no preasure on them, just hold on the plastics, i think i will give the weld and re tap a go

 

[graffian]

You could just buy the taps and a bag of inserts.

 

[jugs]

If you weld & tap, expect to break the odd tap, you can often get hard spots.
Can you use a nut & bolt ??

Thread repair kits, I got one of these click 5-6-8-10-12 mm for £50 & it's resonable quality.

 

[RedOrZed]

If you weld & tap, expect to break the odd tap, you can often get hard spots.
Can you use a nut & bolt ??

Thread repair kits, I got one of these click 5-6-8-10-12 mm for £50 & it's resonable quality.

Cheers that looks pretty useful, will bookmark that till after Xmas

 

[welshpug]

I'd get a time-sert fitted, they are stronger than a Helicoil.

downside is that they are not cheap to buy the tools and kits, so best to get someone who already has one to sort it, my local cylinder head specialist has the kit, and a mate that is a mobile mechanic is looking to get one himself to save the callout and charge per insert.

Wurth is one manufacturer that does them, not sure who else.

 

[Furry Freak]

Could you not drill it out very slightly and put the same sized Rivnut in there? Doesn't matter if you strip it again, you just keep putting a new Rivnut in. If all it's holding bodywork and fairings etc, this should be more than adequate. I use them all the time.


FF

 

[Sam(GTD)]

All these suggestions but we don't know:

What type of section are these threads in? (tube frame with welded studs i presume?)
How critical is positioning with respect to face elevation? (i.e could you weld a tab onto the surface which would raise the component, say, 5mm?)

It could be a very simple, cheap job.

Jugs is right tapping welds is terrible! esp dirty welds!

 

[Grrrmachine]

If you're going to use thread repair kits, I do NOT recommend helicoils or any of that type (spring-style inserts). They are flimsy, need to be replaced almost every time you undo that bolt, and have a very fiddly insertion procedure (involving the snapping off of a tang strip once the insert is in situ; if this is engine work, dropping that tang can be fatal to the engine)

I use steel sleeve inserts: no idea if they are made in the small sizes you need, but if you can get them, they're a damn sight better than helicoils.

 

[Garreth]

Thats what the Wurth timesert's are like.

Cost more but MUCH better long term.

I'd be tempted to try using a rivnut as has been suggested - steel or stainless ones are quite tough, if they start to spin re-tighten them and replace them if they strip !

Garreth

 

[squazy84]

mild steel yes?

 

[pondy]

threads that need to be repaired are basically a metal plate welded onto a tubular frame, the plate just have a hole drilled in and a nut welded onto the back, but in a place that it cannot be cut off and a new one welded back ok. just on a tight budjet
sam

 

[Sam(GTD)]

Thought that's how they would be, you may be able to get a good length rivnut for this.
Honestly tho my first port of call would be to see if you could get away with re-tapping it, upsize with the same thread pitch/tpi so you keep as much existing material as possible.
I'm sure the threads arn't completely stripped, unless your frame is made of butter. The combination of upsizing will make it nice and tight again, even just 1mm.

It's not a structural part but obv for them to have stripped anyway they must have had lots of forces applied......it's worth giving it a go then if it's rubbish try repairing it with weld.

I don't think it's worth the bother flapping about with threaded inserts/helicoil, they'll likely be weaker than a re-tapped hole anyway (because you have two points of contact and more leverage not one)

 

[chunkolini]

On a budget?
Try this if you have access to oxy/acetylene kit.
Drill the hole out until you can fit a nut the right size in there, push the nut in and braze it in place, run a tap through it to make sure it is clear. Job done. I have done this lots of times and usually did not need to tap it. I have not tried this, but if you counter sink round the nut you could weld the sucker in (Mig/Tig, Tig best) and grind the excess off. Providing these fittings can not kill people if they fail.

Chunko'.

Chunko'.

 

[pondy]

thanks for all the help so far

the only reason the threads are damaged is because the bike is stripped down so often, with the racing they take a beating so you need to keep on top of maintaince

 

[Furry Freak]

I've said it once, but I'll say it again. Sounds like a job for a Rivnut. Done in seconds. No tricky welding, brazing, heating, hammering, banging or swearing.

Just don't by a really cheap tool. They are a waste of money. Yes, you can put them in using two spanners and four pairs of hands if you are a tightwad. Just buy a tool. Memfast are probably the best ones.

FF