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#1 DUF2

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Posted 19 November 2020 - 11:44 AM

I have decided to use Rivnuts to attach the wheel arch spats on my Elf.

I am using M4 rivnuts and used a 6mm drill, but one of the rivnuts has pulled through when I tightened the screw.

anyone else had t(is problem?

am I doing something wrong?

 



#2 GraemeC

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Posted 19 November 2020 - 11:58 AM

Just sounds like it hasn't clenched up far enough when installed Gordon.

Aluminium ones are a balance between getting  a good grip and not pulling the thread out of them, steel ones can be tricky as they need much more force to get them to deform and grip.



#3 DUF2

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Posted 19 November 2020 - 03:47 PM

Just sounds like it hasn't clenched up far enough when installed Gordon.

Aluminium ones are a balance between getting  a good grip and not pulling the thread out of them, steel ones can be tricky as they need much more force to get them to deform and grip.

Graceme, maybe I didn’t squeeze tight enough. I have heard stories of the small mandrel snapping so didn’t want to overdo it.

perhaps I should use a bolt to compress the Riv nut more before I use it as a fixing.



#4 GraemeC

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Posted 19 November 2020 - 06:04 PM

Yes I have had a mandrel snap before, but as long as you're careful not to put any side loading/twist on it then it shouldn't happen.

Using a bolt can sometimes work well



#5 Johnmar

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Posted 19 November 2020 - 06:08 PM

Just sounds like it hasn't clenched up far enough when installed Gordon.
Aluminium ones are a balance between getting  a good grip and not pulling the thread out of them, steel ones can be tricky as they need much more force to get them to deform and grip.

Graceme, maybe I didn’t squeeze tight enough. I have heard stories of the small mandrel snapping so didn’t want to overdo it.
perhaps I should use a bolt to compress the Riv nut more before I use it as a fixing.

Just a thought: my rivnuts are screwed onto the mandrel. But if the thread of the rivnut might not be strong enough for the "compression/colapse" initiated by the mandrel, why not:


1) drill the 6mm hole
2) screw the rivnut onto the mandrel
3) insert mandrel with rivunt into hole
4) insert onto the manderel (thread sticking throught the rivnut at the backside) whasher and a 4mm nut from behind, and turn it thight up against the rivnut.


The washer and nut will secure onto the mandrel, and therefore it will (part of) the load for the rivnut thread when compressing/collapsing the rivnut sleeve weakpoint.

I hope it is a bit clear what I'm trying to bring acros)

#6 Tornado99

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Posted 19 November 2020 - 06:34 PM

Plenty of videos online showing how to use a couple of nuts, washers and spacer to set rivnuts/nutserts without special tools or mandrels. For alu types, ive learned the ones included with low cost setting tools tend to be a very weak alu alloy, not the 6061 or better type using in most high load work. The poor ones really tend to strip out easily.

#7 DUF2

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Posted 19 November 2020 - 08:11 PM

Just to make things clear, it was not the bolt stripping the thread of the rivnut, it was the rivnut pulling through the panel.



#8 sonikk4

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Posted 19 November 2020 - 08:31 PM

Something to add to this and using Aluminium rivnuts is the dissimilar metal issue. After you drilled the holes did you paint them prior to installing the rivnuts??



#9 Tornado99

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Posted 19 November 2020 - 09:27 PM

Would not worry too much on dissimilar metals issue. Just think of the engine with all the alu parts bolted to steel etc. There are all sorts of fittings around your car with dissimilar metals. In the marine industry, stainless and alu fittings are used together in many places (alu mast & beam fittings using stainless rivets/bolts etc) without major issues. As long as moisture is controlled by using a grease or sealant on any unpainted areas, you'll be fine. 



#10 nicklouse

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Posted 19 November 2020 - 10:54 PM

If it has pulled through you did not squash it enough. If you are worried about breaking the mandrel just watch the side loads. Been there done that. As said you can go back in with a bolt a nut and a washer to finish off the set.






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