Help me with imperial thread stem bolt...

[medoramas]

It really is an imperial thread bolt. First person I spoke to was a maintenance guy/engineer at my work place (who is also maniac rodie rider...) and he tried to find one in his biiiig bolts & nuts collection, but every single one had a metric thread. He seemed to be surprised to see that thread on an Orange product. I've got 5 other bolts on the stem and they all are such a stupid things...

To make it clear - it snapped because of my stupidity, nothing else. Had an issue with the head set (it was getting loose, all sorted now) on my way to work and I decided to clamp the stem a bit "more"...

 

[pete_mcc]

I've got 5 other bolts on the stem and they all are such a stupid things...

So if there are five other bolts then that suggests that the stem is a modern, ahead stem with a removable clamp, ie 2 bolts at the back and 4 at the front. If that is the case then they are certainly not imperial as the stem would have been made in the late nineties. No taiwanese factory made stem (and almost all OEM stems are made in the far east) would ever use an Imperial bolt, they wouldn't even know what one is as it is not a standard measurement unit and hasn't been for many, many years. Add that to the fact that I can't think of a single bolt maker who would do a metric head on an imperial thread.

I realise that you have been convince by an 'expert' (in the same way that I am an 'expert') but the logic just doesn't add up at all.

 

[pete_mcc]

Just as a thought, have you tried removing one of the other bolts on the stem and seeing if it fits into the offending hole to see if the thread is fine? At least that way you can rule out the need for retapping.

 

[FluffyChicken]

Why did you mate not just measure it to find out.

I'd still agree with the above though. Picture of full stem anywhere ?

 

[WD Pro]

By 'eye' that thread looks a little more course than M6 :?

Imperial stuff on modern bikes ? dont bet on it not existing ...

But I do agree that it will be very rare

WD

 

[medoramas]

Yes, that is an ahead stem. And yes, I took the bolt from the handlebars clamp and put it on the steerer clamp (to replace the broken one) - so now I'm missing the one on the hb clamp. They are definitely imperial threads, I've just taken a picture of a standard, metric thread bolt and the one of my stem - the difference is radical. I'll upload the pic this afternoon - I'm working away from the computer today in a place where 3G signal is a dream...

 

[danson67]

I think you're right on the Imperial thread...looks like a 1/4" UNC to me.

Below L to R: M6x1.0, 1/4"x 20 tpi (UNC), 1/4" x 28 tpi (UNF)

The UNC thread should be about 6.2mm diameter, 5.8mm if it's an M6 bolt.

Metric head on an imperial bolt would be a really freaky special, so that's unlikely. If it is an Imperial thread, the 5mm AK fit is probably just a worn key fitting in the standard 3/16" (4.8mm) Allen key socket.

All the best,

 

[medoramas]

Inside the bolt (where the allen key goes in) there is a letter K, if that's any clue... I've just heard that there is a guy in my town that makes nuts and bolts. I'll see what he says

 

[pete_mcc]

By 'eye' that thread looks a little more course than M6 :?

Imperial stuff on modern bikes ? dont bet on it not existing ...

I'd quite happily lay money that Orange never specced imperial on their bikes, or any other major maker of bikes for that matter. HL would undoubtedly made the stem have never specced imperial and I'd bet that if any other Orange owner on here checked their stems they would be m6 with a 5mm key.

I just can't see Orange, or all of HLs other clients, using their metric keys all over the bike and then swapping to their imperial keys just for the stem.

Maybe someone else has swapped them out afterwards for these imperial ones that then tapped the threads out and helped snap that over torqued bolt.

Either way, I wouldn't be using a stem that's already been so over torqued that the bolt has snapped and that appears to only use imperial.

 

[pete_mcc]

Just as my final thought, if you lookat the third thread down there is a nice shard of bolt thread or hole thread, meaning that it was badly threaded or seriously over tightened: