Recessed 4mm bolt to torque

[Monsieur Remings]

Okay, I have just bought a new 25mm setback FSA seatpost and was going to buy a torque wrench to go along with it. I have already in my possession a 5nm Torque Key but I need 7nm for the seat clamps. The problem is that despite finding a reasonably priced wrench, there doesn't appear to be a fitting that will reach the bolt in the recess of the seat-post.

Does anyone either have any idea where I can find such a fitting, whether or not they exist or should I torque it with my existing key to 5nm and give it a little tighten manually? What do you all reckon?

 

[black'n'yellow]

I've never used a torque wrench on a bike, but if you're determined to use one then I would have thought that 5nm plus a bit more would do the job. 7nm doesn't sound like much anyway, not to hold a seat in place.

 

[GrumpyGregry]

doesn't an allen key 'bit' from an appropriate socket set fit both the torque wrench and the recessed bolt?

Halfrauds sell them in sets or indiviually.

 

[Monsieur Remings]

Yes, am sure they would fit but whether it would reach may be another matter, Greg.

I know what you mean black but 7nm is what they recommend. There's just little point n spending the money on a torque wrench when the fitting isn't long enough to reach the recessed bit.

Any other takers?

 

[slowmotion]

MR, what size drive is the wrench, 3/8", 1/4" or whatever ?

EDIT: search on ebay for "hex bit " and you will find loads of stuff like this...
http://www.ebay.co.uk/itm/15PC-METR...t=UK_Hand_Tools_Equipment&hash=item3f171ab8c5

or this.....

http://www.ebay.co.uk/itm/FRANKLIN-...t=UK_Hand_Tools_Equipment&hash=item3a7650e6c9

 

[GrumpyGregry]

MR How recessed is the bolt head?

My hex sockets are 30mm long, and longer ones are available.

 

[Monsieur Remings]

Okay, thanks people this is really helpful, the recess isn't that deep, maybe 15-20mm only so a 30mm should do it but I was going to buy this...

http://www.wiggle.co.uk/bbb-btl-73-torqueset-torque-spanner-set/

...which is a 1/4 inch. I'm sure I can find the correct length, size from the links you've given Slow and Greg, thanks.

However, what does concern me and I might be wrong is that, surely the length of the socket makes a difference to the force applied, or am I wrong? Is the torque wrench linked, which seems a fairly cheap one, good enough to know the difference when a longer length socket is used opposed the standard shorter ones included with the wrench?

Or am I talking bollocks? Thanks again for any input.

 

[slowmotion]

The length of the socket (and the hex key) makes no difference to the the torque that the wrench applies. Torque is a radial force applied at the same level at any point on the drive shaft. It doesn't matter how long that shaft is. As long as the shaft itself doesn't twist under stress ( and it won't ), everything will work fine.

I would be a useless teacher....

 

[Monsieur Remings]

Thanks Slowmotion, your input is much appreciated.

 

[slowmotion]

My pleasure!