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So I managed to over tighten the uppermost pinch bolt on my sons stem. Bottom bolt is in fine and I left the top one alone the second I realised. Question is what to do next.
How do you know you've overtightened it?
Torque Wrench?
Stripped Threads?
Cracked Carbon Bars/steerer?
Guess?
If you haven't stripped the threads or broken anything, just equalise the two bolts and remember to tighten evenly next time...
I was lucky in that I had a tap and die set, and the next size bolt up knocking around. Drilled it out, tapped it and put the bolt in more carefully.
Cheap tap and die set was about £6 if I remember right but there might be someone nearby that has one if you don't.
What lerk said - if its stripped I guess you can re-tap it or just run it, keep an eye on it and see if it works OK
Thanks for the replies. Just rushing and saw the bolt move without any extra thread showing. Dumb I know.I will back them both off and reassess. It's my sons bike so no risk taking.
Both bolts backed off gently and okay. Waiting on a better torque wrench. Thanks again.
I would put a heli coil thread insert in. They are stronger than holes of the same size without a insert.
If I can't achieve the required torque then I may use a insert. That's a great idea thanks.
No worries depending on where you are I could loan you a kit
They don't need to be that tight, and if it needs a helicoil something is clearly wrong!
If you cant achieve the desired torque i suggest both a new torque wrench with certification and some training on how to use it . Torques for stems are in the region of 5-10nm. Something is wrong if your stripping threads.
Heli coils are not stronger as Larry suggests. They add a variable into the mix, yes steel bolt/screw into a steel helicoil into ALU, maybe but you still have the less hard ALU holding the helicoil
I have said time and time again if you can't guage 10nm torque by experience you should probably not use a torque wrench (whether calibrated or not) as you are not cut out for tools.
And a torque wrench certifaction means sod all, time and time again I have seen Wrench's (with in cal stickers) not making correct torques.
Unless you check them each time they are as useful as my calibrated arm, 3 white knuckles, or whatever you use.
For pinch blots you must have strippedheads for it to be over right. Don't worry!
I always use one of these now, I've got one at home and one at work
http://www.bontrager.com/model/08370
Bin it, not worth the risk of it giving 'way'.
And I always use one of these, carbon or not.
Yes thanks for that but I know how to use one and managed to reach the desired torque with the bottom bolt but the top one appeared to slip suggesting I may have managed to strip the thread somehow. And I tightened them incrementally and alternately by the way. A borrowed wrench did the trick, no stripped thread thank goodness. I am at a loss as to what exactly happened to be honest.
Your torque wrench has been dropped/mishandled and is under reading. Get it on an analyser and see what's what
Just a thought how many people with torque Wrench's or soltorks, know how often these things should be serviced,and then have them done?
Stu174 helicoil inserts are much stronger than standard threads. The thread wire works in two modes rather just straight sheer.
I can send you a paper if you want?
Either way if you want it dome I am Hampshire tadley
TBH torque wrenches are fine if used properly, calibrated every five minutes, kept in a safe lined with fairy dandruff and french lacy knickers etc etc.
Unfortunately most torque wrenches don't lead that life, so I'll continue to use my own judgement, which also goes with me out on the trail unlike most torque wrenches.
Send me the paper please, love to see how a hard material in a soft one will increase strength in a 'pulling force'
Email is stublackbourn at hotmail dot co dot uk
Ive seen some horrendously stored torque wrenchs , people who use them like ratchets breaking out bolts , or just chucked in a drawer with other wrenches not in box. Ive pulled wrenches out in shops only to find the mic is still screwed to the last torque setting. My own wrenches are stored in their blow moulds inside my tool box with nothing on top and the mic fully wound off , they were checked out at work on the inspections calibration equipment. Ill probably get them done once a year but then i rarely use em as ive been doing bikes long enough i know what stuff needs to be. Cars on the other hand i use my torque wrenches for.
Even just pulling your wrench wrong will give a false reading.
This guy shows it in simple terms
http://www.clubgti.com/showthread.php?256235-Why-Helicoils-can-be-better-than-the-original-thread!
Nice picture
It increases it's strength as it's a Bigger circumfrance for the sheer mode to react against