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Has anyone successfully used thread repair inserts as a 'thread reducer'?
I recently picked up something which has been modified by the previous owner to use M12 eyelet bolts instead of the standard (for that item) M8 wing bolts.
It's annoying, and unnecessary - the standard M8 bolts are fine, and the M12 eyelets add extra weight and are less functional than the originals (which are designed to be regularly tightened and loosened).
I was thinking of getting a thread repair insert into the M12 threads to reduce it back down to M8 - perhaps epoxying it in.
I was considering something like this:
https://shop4fasteners.co.uk/metric-thread-reducing-inserts-m8-m12-x-15mm.html
Any reason not to?
Never used a reducer but have used hundreds of Helicoils and all have been fine.
I've used smaller ones, look like they should be fine. Depends how tight you need to screw in the M8 bolts, so they may undo when you take the bolts out.
Double check then triple check the spec of the threads, inner and outer!
Also remember you've not got two threaded interfaces and I'd be very concerned that when you tighten and loosen the connection, or through ordinary use, are you going to end up with a loose M12 connection and the part failing or being unable to get the parts apart?
/edit - and the real issue I'd always try and understand is why has the previous owner (though it my case, normally the previous designer) done this? Is it because
1. He lost a wing bolt or damaged one and wanted to replace them all with something he had to hand (having M12 eye bolts and the thread tapping kit..?)
2. He couldn't do wing bolts up tight enough by hand so replaced with eye bolts and a bar to tighten them?
3. He's a numpty and likes breaking stuff
4.????
and the real issue I’d always try and understand is why has the previous owner (though it my case, normally the previous designer) done this? Is it because
1. He lost a wing bolt or damaged one and wanted to replace them all with something he had to hand (having M12 eye bolts and the thread tapping kit..?)
2. He couldn’t do wing bolts up tight enough by hand so replaced with eye bolts and a bar to tighten them?
3. He’s a numpty and likes breaking stuff
It's a cymbal stand, and based on what I saw of how it was previously used to support very large drums, I suspect a combination of 1 - 3!
Basically in the photos I had it was set up 'wrong' (i.e. I wouldn't have tried to support such large drums off the cymbal stands at those angles as they would slip, which is exactly what I think he was trying to prevent with the larger bolts).
I suspect the former owner may have had an engineering background - the new threads are well cut, and TBH other than being annoying to try and tighten an eye bolt it works fine, I just find it a bit offensive to the eye and like stuff being as close to original as possible!
Also remember you’ve not got two threaded interfaces and I’d be very concerned that when you tighten and loosen the connection, or through ordinary use, are you going to end up with a loose M12 connection and the part failing or being unable to get the parts apart?
Depends how tight you need to screw in the M8 bolts, so they may undo when you take the bolts out.
That's why I suggested epoxying the inserts in - would that be a bad idea?
That’s why I suggested epoxying the inserts in – would that be a bad idea?
Normally you'd threadlock them in - I'd have thought that that would be sufficient?
Check the thread pitch, but it should work fine.
I fit threaded inserts to damaged crank arm pedal threads, I use red loctite so they dont come out when the pedal is changed, can be removed by heating to soften the loctite.
That’s why I suggested epoxying the inserts in – would that be a bad idea?
Loctite thread lock comes in different strengths. From “this will hold it a little bit tighter” to “you’ll never get this undone again”. Choose based on whether you think you’ll need to undo it again ever and how tight you think you need it to hold. Some can be heated to undo them.
Thanks all, much appreciated!
We fit them at work and use a Bridgeport to drive them in as they cut their own thread. You’ll need a fair amount of torque to drive them in. If you don’t know what you’re doing you’ll end up with a 12mm hole. Good luck.