Are torque wrenches worth it?

T wrenches are calibrated, and tested to ensure they are accurate. Modern ones are, very, especially the expensive dig ones. You can do it yourself simply to well within 25% accuracy with a rod and a weight.

All the wrench is doing is telling you the force being applied to the object being tensioned. They do not, can not, and do not claim to, tell you about what's happening to the bolt or whatever, beyond the power being applied to it's head.

^which includes overcoming friction, which could be a considerable variable, depending on various factors. You're not saying anything different from me, so we seem to be in agreement.

I thought that one spends a bit more money on a torque wrench in the hopes to have a better sense of how tightly one fastens a bolt and a nut, not so you can get a reading of a number of measurement about how much rotational force one is applying to turn the nut. With a plain washer, internal teeth lock washer, split lock washer etc...

They are spanners, not wizards. You need to use the correct nut, washer, lube etc arrangement specified by the manufacturer or whatever, for the job at hand, as well as making sure threads are clean, debris free, and so forth.

And you are focusing on a small part of the spectrum of use. They are not only used for "cranking up nuts" purposes, but also for accurately setting springs, hydraulic pressures, etc etc.

In the realm of the home bike mechanic, they might stop lummoxes twisting the heads off/rounding Al bolts/ripping out inserts/cracking stuff, or making sure rotor bolts/cranks don't come loose etc. Manufs give settings allowing error margins for these purposes. Try guessing 40 ft/lbs pressure and see how accurate you are.

They are spanners, not wizards.
My point, exactly. You made the accuracy statement and went all over the island discussing everthing else except the bit I wanted your expertise, your accuracy claim. Don't get me wrong. I want to buy a torque wrench and trying to find a good reason to buy one. So, yes, it's a personal question; I'm not trying to do the world a favour. I used to cycle competitively and was my own mechanic; I broke a fair number of things like wheels, seatposts, handlebars, cranks, pedals, brakes, forks, whatever, but never had any issues with overtightening bolts of any kind. Like yoav said, we didn't use fancy gadgets but were fine. We made our tyres rock hard when racing indoors, we made it reasonably hard to the touch when racing outdoors. Pressure? No clue. Now I use a track pump with a proper gauge, but back then, things like pressure gauges were the sort of things that the guys who finished last insisted on using. I'm veeeeery slow now.

It's not MY claim. They measure torque accurately - it's not rocket science.

They measure torque accurately.

It's not MY claim.

Understood. No further questions.

As others have said, it depends on the manufacturer and their chosen level of accuracy. I have a Roebuck wrench whose rrp is a lot higher than a draper but the certification vindicates this matters esp for light weight/delicate parts.

Tighten until you hear a slight cracking noise, then back it off 1/8th of a turn.

Done!

Carbon seatpost collapsed under my weight today. I haven't tighten the bold enough (didn't want to snap the carbon).
Now the seatpost's farked.

NO! After I saw you????

apropos nothing, I just scanned your avatar.

+1

NO! After I saw you????

No, before. By "collapsing" I meant went all the way into the frame, not snapped. I had trouble pulling it out. Badly scratched now.

I've been looking at seatposts on eBay today- to the untutored eye there is not much to separate the £50 from the £250 seatpost.

I hope you scratched an affordable one Kris, and sorry to hear of your misfortune.

oh Kriss.

I don't know how much is it worth or where to buy one right now :-) It's not very visible since I used some grease on it, but the top varnish is stripped.

Weight saving on seatpost

Sell it to dammit for twice it's original price as it's a couple of grams lighter.

Yeah, this one's one of those £250 ones like.

No grease, you need assembly paste on it to increase the friction betwixt post and seat tube and probably a coke can shim too. PX seatposts have got "form".

Thanks. I wouldn't dare to grease a carbon seatpost where it get in contact with the frame :-) Only rubbed down the stripped bit above the insertion.

Assembly paste? I will look into it. Cheers.

I have a tube of Tacx carbon paste but they do sachets that would be enough to put together full carbon to carbon everything build. It's just tiny beads of plastic in a gel but it stops any reactions between materials and allows you to keep torque down too.

Anyone got any experience of the EC90 full carbon?

I have a tube of Tacx carbon paste but they do sachets that would be enough to put together full carbon to carbon everything build. It's just tiny beads of plastic in a gel but it stops any reactions between materials and allows you to keep torque down too.

Ordered a tub of Finish Line "Fiber Grip" for now from Wiggle, as I had a voucher about to expire.
I completely overlooked that aspect of bike assembly. I mean, I'm prepared for everything with steel and alu, but i"m hopeless with carbon fibre.

Has Diggerz buy that torque set in the end? I must be nice to him.

EEI, I am clueless about carbon bike parts but do a bit of work with carbon composites. Is the scratch deep enough to expose the woven carbon under the outer composite layer? What is under the woven carbon -- solid composite of some thickness, hard foam, or something else and then another layer of woven carbon?

I think it's a cosmetic damage to the outer layer only, but will inspect it later.

If so, just a puff of clear lacquer rattle-can will do nicely. Make sure you used mat/silk/gloss as appropriate.