How do you verify or calibrate a torque wrench (for light home bike mechanic purposes)?
In other words, can I "trust" a cheap torque wrench not to crush delicate components or round off fasteners?!?!
Know somebody who can calibrate? I have a buddy who spanners on helicopters so I get him to check mine. It's how I found out my OG X-tools wrench was of the belief that the stated numbers were an artificial construct.
Wrench was a hippy.
There’s a tool shop local to be that does then, so there must to somewhere close to you that’s similar.
I guess there must be a way of doing it yourself too, possibly with a vice and some weights?
guess there must be a way of doing it yourself too, possibly with a vice and some weights?
Exactly that. . Bit of simple maths for the lever length and you know the force you applied
Yep you can do this to do a basic check that things aren't way off. There's a few good guides online.There’s a tool shop local to be that does then, so there must to somewhere close to you that’s similar.
I guess there must be a way of doing it yourself too, possibly with a vice and some weights?
I've never had mine done in years, although should have. It was stated that they need calibrating annually but I'd guess that it's number of clicks that puts them out.
For delicate stuff (stems, carbon bars etc.) I've taken to using pre-set torque collars (I have some 4, 5 & 6Nm ones from Topeak & Lifeline). They slip at the pre-set torque so have the added advantage that you shouldn't actually be able to over tighten anything.
There are various calibration tools available online (Amazon have some around £50) but like all tools there's going to be a whole range of cost & quality.
There are various calibration tools available online (Amazon have some around £50) but like all tools there's going to be a whole range of cost & quality.
And then for it to be in any way a reliable calibration, your calibration tool needs to come with a test certificate, (very unlikely for 50 notes) and be re-tested to a traceable standard occasionally.
I work for a cal lab, and though we don't do it ourselves we see plenty of torque wrenches for sub-con calibration. Looking at the data once they're in spec they very rarely then go out. I expect they're looked after and not left at high torque settings when not in use.
For low torque bike components I'm not sure I see the point. I work to the rule of do it up until it stops moving and then add a bit more if it slips. For higher torque applications it's easy enough to check your torque wrench using a measured length lever and weights.
it's easy enough to check your torque wrench using a measured length lever and weights
That's what I'd be doing if I could be arsed.
(years ago, somebody on here very kindly offered to calibrate a couple for me that were pretty old but life intervened for a few months and I then forgot until, err, just now)
Here's my heath robinson calibration setup
Turns out my 1 year old Wera that set me back about £150 might not be very accurate
That's 5.3kg of logs, 97mm radius, should be 5Nm
The torque wrench had to be set to around 6Nm to lift it without clicking. It was very repeatable. Granted that's at the low end of the range of this torque wrench, maybe it's more accurate at higher torque.
I invite armchair engineers to poke holes in my method 😁
I think it is Canyon that has the WiFi torque wrench that auto adjusts to the right setting as they move round the bike - I'd love that, but very much not cheap!
Cheap torque wrenches aren’t totally bad I think, they’re just a bit inconsistent, and most failures come from user error rather than the tool itself. In my experience, budget wrenches are usually pretty accurate through the middle of their range, but they can struggle at the very low end or if they’ve drifted out of calibration without you realising it. Most of the crushed parts I’ve seen were torqued to the right number but assembled incorrectly in the first place.
As an aside, I've heard that electronic torque wrenches that use stress gauges (as in power meters) don't go out of calibration, don't lose accuracy at the ends of their range and can accurately measure much wider torque ranges (no sure if one could be found that would cover the whole range of bike torques, say 5-50Nm or similar).
Are these the way to go in future or are they prohibitively expensive or flawed in other ways (mechanical wrenches still seem to be the norm)?
As an aside, I've heard that electronic torque wrenches that use stress gauges...
I imagine some of the curmudgeons here will be rolling their eyes at the thought of another item to remember to charge the batteries occasionally... 😉
I imagine some of the curmudgeons here will be rolling their eyes at the thought of another item to remember to charge the batteries occasionally... 😉
Well I changed from a digital 'vernier' caliper to an old fashioned manual one for that very reason!
We've got a few digital ones (Facom and Snap On) at work up to 1200 Nm and they do seem pretty stable over a number of years use (and get calibration checked, plus we have 3 sizes of calibrated digital wall mounted setting units). I've got loadcells (also strain gauged lumps of metal) that are +40 years old and done +100 million fatigue cycles without major changes). Also done quite a lot of torque and clamp load testing, ultrasonic stretch measurement etc.
5 Nm Vs 6 Nm at the bottom end of a mechanical wrench is pretty normal.
But I rarely use a torque wrench on a bike anyway 😀
The majority of bike torques are to stop you squashing or stripping things. Very few bike joints are actually critically tightening to obtain optimum clamp loads or yield torquing a single use faster.
https://www.boltscience.com/pages/tighten.htm
I like my bending beam torque wrench...... *Curmudgeonly laugh*
I like my bending beam torque wrench...... *Curmudgeonly laugh*
You may laugh but I genuinely do like them. No RSI in my wrist from setting then backing off after use and if the dial says zero when I pick it up then it’s likely still as accurate as it ever was
As someone who doesn’t own a torque wrench yet, but has one in mind for Christmas, can I ask what the OP (or others) are doing that need such accurate, calibrated wrenching? Im genuinely interested as to what components are going to be damaged by using 7Nm instead of 6 for example?
I guess there must be a way of doing it yourself too, possibly with a vice and some weights?
Hmmm, that's not really "Calibration" the best you can call it it "verification" perhaps(?)
A calibrated tool or measurement device will be tested, then adjusted to ensure it's readings are accurate (or at least within an acceptable level of deviation from reality).
TBH you're probably as well off buying a new tool from RS or wherever, with 12 month of certified calibration (which of course starts drifting after the very first use) as you are stumping up for someone to test and recalibrate a Torque wrench. Or just accept that even a well calibrated Torque wrench is only ever going to get you in the ballpark, and +/-15% is probably what you'll get at best.
Realistically I'd be more concerned about your Tyre pressures, people seem to obsess over having the exact right +/-0.5psi value; as read on the decade old gauge that came with their Track pump, that's spent most of it's time in an out-building with no temperature or humidity control. you sure that Minion is at exactly "22.5psi" buddy? of course it is...
I guess there must be a way of doing it yourself too, possibly with a vice and some weights?
Hmmm, that's not really "Calibration" the best you can call it it "verification" perhaps(?)
A calibrated tool or measurement device will be tested, then adjusted to ensure it's readings are accurate (or at least within an acceptable level of deviation from reality).
Adjustment isn't needed for calibration. Readings don't even need to be accurate, just repeatable and traceable to national standards.
TBH you're probably as well off buying a new tool from RS or wherever, with 12 month of certified calibration (which of course starts drifting after the very first use) as you are stumping up for someone to test and recalibrate a Torque wrench. Or just accept that even a well calibrated Torque wrench is only ever going to get you in the ballpark, and +/-15% is probably what you'll get at best.
That depends on the traceability of that certificate. Plenty of certificates that I see supplied with "calibrated" electronic instruments are basically made up. Torque wrenches aren't complicated though and the branded ones that pass through work appear to generally be within their manufacturers specs year after year.
the decade old gauge that came with their Track pump
I once discovered the gauge on my old cheapo track pump was out by 30psi!
Here's my new and improved gauge, hand drawn with sharpie, calibrated via squidge test
The majority of bike torques are to stop you squashing or stripping things. Very few bike joints are actually critically tightening to obtain optimum clamp loads or yield torquing a single use faster.
This is a good point. The only thing I religiously use my torque wrench on is Shimano cranks pinch bolts.
Lots of torque tools at work that are calibrated annually. Lots of them fail calibration, even the expensive digital ones from Snap-on et al.
Having said that, failures are generally out by +/- 10% of the indicated torque. I would say not enough to either cause damage or allow a bike component to drop off.
For delicate stuff (stems, carbon bars etc.) I've taken to using pre-set torque collars (I have some 4, 5 & 6Nm ones from Topeak & Lifeline). They slip at the pre-set torque so have the added advantage that you shouldn't actually be able to over tighten anything.
Do these not go out of calibration eventually as well or are they more stable? I was thinking about getting one of those with the swappable heads for different fittings, as i only ever seem to use the 5nm setting on mine anyway for stem bolts/seatpost. Only just got round to buying a torque wrench this year and realised how much I've been overtightening everything for years 🙂 I just got a cheap Crivit one from Lidl and dropped it the first time I used it, so not sure how accurate it is, though.
I have torque wrenches and I have fasteners with specified torques, why not put them together from time to time.
Interestingly, I have two digital, two beam deflection type. My only clicky ones are the 5Nm preset one and the big one for car wheel nuts.
So long as they all agree with each other, I'm not regularly calibrating
Having said that, failures are generally out by +/- 10% of the indicated torque. I would say not enough to either cause damage or allow a bike component to drop off.
that's what I've always suspected - any loss of accuracy on a reasonably good quality tool (and probably even on the cheap stuff) isn't going to be significant for bike use where theres always going to be a reasonable margin of error (given most mechanics aren't using torque wrenches most of the time anyway)
I want to not massively overtighten small stuff and things where I might be tempted to (eg shimano crank pinch bolts, seat post clamp, suspension pivots) and get enough but not massively too much (so as to strip) things like the chainring on my ebike motor cranks, bottom bracket, or the reverse thread on a UDH
Using a torque wrench doesn't guarantee things won't slip - both K and I have had Ergon grips slip on the carbon bar which has grip treatment on it when tightened to spec. and suspension pivots still go loose and I've had a properly torqued BB get movement and creak.