Sell the torque wrenches and buy a new stem.
Tighten allen bolts up holding the short end of the allen key, long end in the bolt. It is very hard to overtighten doing this, and will get your bolts in the right ballpark tightness most of the time, maybe except for crank arms.
They're two rules I usually adhere to TandemJerry, why I panicked and didn't yesterday is a bit of a mystery. What's particularly gauling is that, as someone has said, once the head had gone there was no torque and I should have been able just to wind the shaft out, instead I made a complete hash of it with a drill!
I shall go out for a ride and try and relax.
s'alrite. I was rebuilding an engine a few years ago and somehow over torqued the camshaft retaining bits in the cylinder head - obviously didn't know at the time.
Started it up, ran smoothly - winner. 5 miles down the road on initial break in run the engine cut out, I thought ****. Got towed home by the AA and went to bed.
Next day, took cam cover off, plugs out, trued to turn the engine over by hand, wouldn't go, double ****!
Out came the tools, stripped the head and both CAMS were scored on their journals and 8 out of 16 retainers were fecked. So one very very expensive lesson in checking things over before you put things back together.
maybe except for crank arms.
for which the correct torque is standing on the long end of the of the key 
Pjay - we all do these things from time to time - as others have said it's all just part of it ! If you want some therapy have a search for a thread from a few weeks back about things going wrong with bike fettling - you are not alone 
here it is :
http://www.singletrackworld.com/forum/topic/most-mind-blowingly-stupid-parts-breakage-youve-had
You can always ring the Samaritans if you're that gutted
Shit happens - standing back and trusting your gut generally works for me.
A silly mistake like this has left me feeling pretty useless and a real numpty...
If it's any consolation, I'm a professional mechanic and I wrecked a £250 wheel bearing recently.
Regarding drilling it out for an M6 bolt or helicoil.
If you've drilled it off centre, it may be hard to get a helicoil to work. depends just how much of a mess you've made of the hole.
Drilling oversize for an M6 bolt may be a better option. If the head of the bolt is recessed into the stem, an M6 bolt head won't fit. Use an M6 button head screw, as it uses a smaller hex key, and grind the outer diameter down.
In either case, I'd say you're going to need it clamped down on the table of a pillar drill, not free hand in a vice.
A torque wrench is only any good if it's actually callibrated properly I've never bothered with one in over 20 years of spannering. Not needed on a bike IMO. For carbon bits maybe..
Thanks everyone, I've been out for a ride and it's still fun with the old stem and bars. I guess I just need to mark it up as a learning experience and carry on.
PJay - Member
Thanks everyone, I've been out for a ride and it's still fun with the old stem and bars.
The best response yet
Added to which - maybe there was a material failure there and that contributed / caused the [initial] failure?
Absolutely, just put it down to experience and don't loose heart over it.
I'd refuse to believe that there is anyone, with any kinda fettling background, that's not found themselves staring in horror at something [similar] and wondering how on earth it happened.
In a similar vein to the camshaft tale above ^ a pal and I once walked [for what felt like miles] along a main road with a big box, collecting as many of the fragmented bits of his motorbike engine as we could find, after he'd replaced one of the bottom end shells and 'bolted it all back up properly' late the night before, in a barn where he was working.
We never did find everything, not that it mattered given that it was completely and utterly annihilated. When we stripped it later that day, it was scary how much damage had been caused, there was almost nothing we could salvage.
I think he mostly wanted it done as a kinda public service, just to tidy up all the bits of metal from all over the road.
What type of torque wrench are you using?
or
The top one isn't much good on lower torques such as your stem and they should always be returned to zero after use otherwise it knackers up the calibration.
It sounds like there was a fault with the bolt or threads, it shouldn't snap being 25% over torqued, trouble is now you have drilled it you can't try the warranty route.
We all make mistakes and even with experience you'll still do it. I recently cracked an alloy head trying to remove a broken exhaust stud which cost me £300 and hours of work. It happens, hindsight is a wonderful thing!
The bolts can be very stiff on sunline stems I always greased mine well
I still don't see the need for torque wrenches, I've never snapped or stripped a bolt through over tightening, and only had a few things loose. This includes wrenching at a few lbs'. I'm no mechanical genius either.
I always put the bolt in & run it all the way down to make sure the thread is deep enough & isnt binding. Crucial with smaller/finer threads.
For it to snap like that I'd wager the thread wasnt deep enough & it was binding before it was actually clamping.
Of more concern would be the accuracy of your torque wrench. That sounds like a low figure for shearing an M5 bolt ?.
And as above, anything under 10Nm go as tight as you can holding the short end of the key.
Al - leaving bolts too loose is nearly as bad as too tight and stripping them.
You do need to learn the feel for when a bolt is tight enough. with your amazing skills in all areas of MTBing I am astounded you dont have this.
Ive effed a Hope XC rear through nothing but anger and a hammer and two shimano XT brake levers by trying to get them to fit over funny bulges on my carbon bars.
OK I admit I skim read this, but was it a steel bolt into an alloy stem? If so the stem threads would have gone long before the bolt snapped I would have thought - therefore faulty bolt, but unfortunately you've drilled it so I guess no come back.
I've stripped threads but never snapped a bolt - seems strange.
http://www.torqueleader.com/products.asp?id=345
tool porn. I've got one for bike stuff and another for doing landrover timing belts, far better than click/break types.
One more thing to consideer.
How were you tightening the stem bolts?
If doing up the faceplate on a four bolt stem, you need to bring all four bolts up to torque together, do not tighten one then the other, then the other etc.
If the faceplate is wonky and you tighten one bolt, then another, the first bolt head can be put under a lot more strain.
If you were to just crank up the bolts to 8nm one at a time, i am not surprised one snapped.
If you smoothly tightened them, in a pattern that means you tighten; bottom left, top right, bottom right, top left. Moving diaganally across the bar, and repeat, getting slightly tighter and tighter each time, then I bet you can achieve the recommended torque easily without snapping anything.
And also remember to grease the threads, so that they turn smoothly and don't bind.
Personally, i would use a t-bar allen key to spin the bolts up, then bring the bolts up to torque as above, probably tightening each bolt seven or eight times by feel. Then check with the torque wrench. By doing it this way i am 100% confident that the stem faceplate i tightened correctly.
And 12nm on a stem seems very very tight. Most modern stems using an M4 bolt are 5nm, the Sunline is 6nm. A fourbolt faceplate holds that bars very tightly and shouldn't need excess bolt tension to hold it.
Hi, it was actually a steerer clamp bolt that went, not a faceplate one. I had been tightening them up alternatively, a bit at a time. I think that I'd realised that I over torquing it but the brain didn't reach the hand in time. I've only got myself to blame, I'm just really upset about it as I'm generally pretty careful. It was a 2-24Nm rated clicker torque wrench by the way and I always reset it to 2Nm (it's minimal setting) before storage.
My old stem that states 12Nm for the steerer clamp is a Raceface Deus (old model), it states 10Nm for the faceplate is a 2 bolt design.
My usual approach to bolts is to do them up by hand to roughly where I think they should be and then nip them up with the torque wrench. In this instance the bolt kept turning and broke before my brain activated. I should have stopped and at least re-checked the torque settings marked on the step. I guess it was a lapse of concentration, but a potentially costly one.
TandemJeremy - Member
Al - leaving bolts too loose is nearly as bad as too tight and stripping them.You do need to learn the feel for when a bolt is tight enough. with your amazing skills in all areas of MTBing I am astounded you dont have this.
My point is you (one, I) CAN do it by hand (can see the need for carbon, cars etc)
Oh I still can't do front wheel lock-ups.
If it's a steerer clamp bolt then can you not drill it right through and fit a top hat sleeve from the far side if helicoiling is not feasible. A cruder way would just be to use a longer bolt with a nut on the far side.
I'm surprised, like others, that the bolt snapped before the alloy stripped. But, yes, we've all done something similar at one time.
I learnt my mechanicing skills on an expensive parentally-funded orange patriot when I was racing DH as a kid.
Cue lots of broken marzocchi stanchions from overtightened crown bolts, stripped BB shell on the brand new, back from warranty front end, three knackered freehubs because i thought it would be a good idea to fill them with GT85 from new, not to mention a set of Ti handlebars I found in my dad's cupboard which I promptly crimped by overtightening them in my stem.
one of many reasons I now shy well away from expensive DH toys!
Thanks for sharing your disasters guys, I guess I shouldn't take it too hard, after all I do seem to have come a long way with my mechanical skills; perhaps I got a bit complacent. It's just frustrating when I realise just how many options I have for not screwing up or salvaging the situation without making it a total disaster. I'm sure I'll be better focused next time!
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