Titanium bolts. Be VERY careful

Sep 2, 2009
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#1
Hey,

So, I bought a new Deda stem last week, which came with Titanium bolts.

On the stem itself, the website, and also on Wiggle, the limit is set to 8Nm for all bolts on the stem (6 bolts in total).

Using my digital torque wrench set to 7.2Nm, I tightened the bolts on the back, connecting the stem to the steerer. All good.

Tightened the 4 bolts on the front, and approaching the 6nm mark on the final bolt...

POW!

I am blind.

Bolt snapped and hit me in the eye.

Cut to today, I am out of hospital, having been told I am a very very lucky boy not to have been blinded. I have a small cut on the inside of my left eyelid which is irritating as hell, and a headache.

And a knackered stem.

So, titanium bolts. I would recommend NOT using them on a stem. Only lose about 8 grams in total by using steel ones which don't have a habit of exploding when tightened.
 

StuInTokyo

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Dec 3, 2010
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#3
Damn.... you are VERY lucky indeed.

When I head down to my workshop, I turn on the light, put on my safety glasses, then the tunes, then my apron, but just tightening some bolts on the stem, wow, I'd not think to wear my safety glasses then :eek: Must have been a faulty bolt, I'd contact whomever you got them from they might have a bad batch from China :(

Glad the damage was not worse.
 
Sep 2, 2009
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#6
I`d also throw away that torque wrench!
If your fork tube is carbon then 8Nm is too much.
Well, this was a rating given on the stem, on the box it came in and also on the website of the people who sell it, so you can't blame me for following their guidelines, can you?

I have contacted the relevant people and am awaiting response on this.

I can imagine that something like this would happen if I had gone over the Nm limit, and was approaching something like 10 or 11Nm, but not WITHIN the limit, and in such a disastrous manner...
 

WhiteGiant

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#7
A rating is a rating, but...

I hope you're not permanently injured because of this, seriously.
I have heard though, that the eyes are "particularly miraculous at healing themselves".

I'm no expert, but I was just wondering how you tightened them exactly.
As far as I know, the "proper" way is to hand-tighten each each bolt first, and then give a 1/4 to 1/2 turn on each (some say, in a criss-cross pattern) to make sure that, before the final turns to the correct tightness, each bolt is at roughly the same tension.
If one bolt was tightened all the way to 8Nm before any others had any tension on them, tightening the other bolts might cause a levering effect on the first, and push it to over double the original tension. ie. 16Nm.

I'm not saying that's what you did, but it might be a possible cause of failure.

I hope is heals soon!
Travis
 
Jan 14, 2007
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japanichiban.com
#9
Travis thats actually the first thing I though of when reading this post.
Me 3. Better to be under than over and tighten the last turns a few at a time from opposite to opposite... front to back, left to right, rinse and repeat... making sure all the bolts are going in the same distance...not unbalanced on one side. Layer, upon layer upon layer, roll it and fold it and roll it again... :eek::bike:
 

FarEast

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May 25, 2009
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#10
The actual torque rating stated on most kit is the max tolerance not the actuall tightening requirement.

My cleats actually state that the max is 8mn but the instructions stat that they should be tightened in cross pattern to between 4-5mn.

As standard practice I normally drom 1-2nm off the max torque requirements for frame fixtures. A classic example of this is my Dura Ace shifters..... torque chart says 8nm but at that rate they are on the bars rock solid and in the event of a crash will basically take the brunt of the truam and probably take the bars with them.

At 6mn they are on nice and tight but if I give them a whack with the palm of my hand I can get them to shift a little and thus possibly give them some chance of surviving a stack.
 
Sep 2, 2009
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#11
Hey there,

Yeah, I knew there would be questions about tightening technique when I posted this.

Of course, I tightened in what I deemed to be the correct manner; tightened it by hand, evenly, in a criss-cross motion until all bolts had exactly the same amount of thread showing in the gap between the front plate, and the main stem body.

Then used the torque wrench to bring it up to 7.2Nm.

The snapping occurred at around the 6Nm mark, and was definitely not due to imbalanced loads, etc.

My eye feels a bit better today. No real visible damage on the skin, but hurts inside, and on the inside of the eyelid.

This kind of raises an interesting issue, doesn't it; what is the correct Nm rating for parts, and which manufacturers are giving correct and full instructions on how to install things?
 

zenbiker

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#12
6Nm isnt enough to snap a 5mm Titanium bolt. My guess is either you made a mistake setting the wrench or its not working properly.
Ritchy makes a Torque Key which is perfect for bars , stems and anything going on carbon. About $4
 
Sep 2, 2009
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#13
I have a 130 quid digital torque wrench, complete with a certificate from the manufacturer stating the results of tolerance tests across its full range.

I did not set the torque wrench wrong.

It was not my fault that it snapped.
 
Jan 14, 2007
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#14
I have a 130 quid digital torque wrench, complete with a certificate from the manufacturer stating the results of tolerance tests across its full range.

I did not set the torque wrench wrong.

It was not my fault that it snapped.
Bad luck. Hope your eye gets better fast...

The day my brother gave me his old racer in 2003 (my first since I was in high school) he was tightening up the seat post for me... as hard as possible... till the clamp cracked in half. Was a good first lesson.
May have to invest in some safety glasses.

I don't have a torque wrench so just go light but firm and play it by feel.
May have to invest in one.
 

GSAstuto

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#16
Hmmm, its very hard to snap a 5mm Ti bolt @ 7nm torque - especially if its threaded into Aluminum. There is obviously some mfg defect, or perhaps as Travis indicated, excessive tension was formed because of unbalanced tightening. Where did it say 7nm anyway? That seems quite high. General rule of thumb is no more than 1.45 the diameter. So - they should be within spec at 7nm. Typically you'd need to torque to at least 2x or even 3x that to get a graded bolt to 'snap'. Also - did you use teflon grease on the threads? Or put it in dry? Did you just whack the wrench down on it? Or smoothly come up to torque? You should tighten in X fashion and then work up the torque slowly in 25% increments. And for the final torque hold at least 3s ever so smoothly 'on torque'.
 

StuInTokyo

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Dec 3, 2010
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#17
If you still have the bits of the bolt, if you could find them, I'd love to see a picture, I'll bet that is shows an internal fault in the metal.

If there was a manufacturing defect in the bolt, the surface will be mostly smooth where it broke, if it was due to fatigue, which I cannot see as the bolt was new, there would be a very rough surface.
 
Sep 2, 2009
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#19
Honestly can not be bothered to keep debating this with you good chaps.

Nothing personal, please realise.

I have been in contact with the relevant people, and the issue is being dealt with.
 
Jan 14, 2007
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#20
Honestly can not be bothered to keep debating this with you good chaps.

Nothing personal, please realise.

I have been in contact with the relevant people, and the issue is being dealt with.
Hope your eye is feeling better.
With regards to the debate, it's all great reading and learning.
As far as technical and getting my hands dirty I'm fairly illiterate.

These threads let me learn a lot of stuff I wouldn't know about.
May even invest in some safety glasses for my cycling tool box.

Thanks for starting the thread. Sorry if we attacked you like piranhas... (or seemed like it).

May be a good idea to start a thread about accidents you've had while doing maintenance. I know I've hurt my fingers a few times...saw my seat post clamp explode in two as a friend was tightening it up for me... :warau:

I'm always scared the pump clamp is going to fly off as I max the pressure in my tires and hit me in the eye like a whip....