Torque wrenches lie!

Laverdalothar

Laverdalothar

Hero member
Location
Germany
I am currently re-torquing my 1000 SFC's head. I have different torque wrenches for different torques, but was never sure - as they are all at least 20 years old - how good they are and if they do their job well or not.

So - I bought me a tool to actually test them. The result was quite shocking I must say... OK - to start with: the tool I bought is controlled, new and tested. Further to that, all 4 torque wrenches showed completely different symptomes, which were repeatable. My conclusion is, that this would most probably exclude a fault with the testing device.

The 4 were from Würth (professional brand), Wisent (somewhere in the middle but not completely bad) LUX (Obi house brand) and Silka (totally cheap crap).


Adjustment precision:
It already starts with the adjustment of the spanners... none of the four was precise, it was more or less an approximation to the correct value. Most of the scales are so imprecise and sometimes the setting can still be twisted despite being locked, that 20Nm could easily be 19 or 21, etc. The higher the spanner, the coarser the scale. Sometimes, when turning the values up or down, the scale did not move at all for a short time, even though the handle was turned. At first I thought there was a little play in it. But the settings actually varied by 1-2 Nm even with a 20 Nm setting 8| Remember: that's up to 10%...

Replicability of the values (same setting, check several times):
Only one of 4 spanners (the Wisent) produced approximately the same values when measured at the first as well as the 3rd attempt (setting 40 Nm, measurements varied between 39.8 and 40.2Nm - OK for me!). With all 3 other spanners, the first click after setting was the highest measured value, the 2nd and all subsequent ones were lower (at 20Nm, first click 19.5, then between 17.3 and 17.5!). Ergo: If you tighten several screws with it, the torque is correct for the first screw, but not for all the following ones... Unless you relax the spanner after each screw and then readjust it. But then you run the risk of not getting the setting right (see point "Precise setting"):rolleyes:

Scatter over the setting range
The torque spanners were very different here. The Wisent, which was really good and precise in the lower range, was a complete disaster in the upper range! With a set value of 120Nm, it only released at over 160Nm!

The Würth triggered OK in the lower range, set at 120 Nm it triggered at 133 Nm :oops:

The absolute disaster was the Sika: completely unclear scale and MUCH away from the displayed values, even in the lower and middle range. I will check the setting again...

Calibratability
I have only tried it on one key so far, but the measurement results were so different that I can't say exactly what the problem was. I will try again now that I have the measuring device firmly mounted (2-3 days ago I held it on the tabletop with one hand only and then tried it - of course it doesn't work...).

Conclusion: I will only use the Wisent and the Würth in future. With both I will adjust the torque with the help of the measuring device, make at least 3 clicks and only adjust when the values no longer change.

I am also thinking about buying a brand-name torque spanner. However, I would like to test one first in several areas with my gauge to make sure they work more accurately then.

Conclusion2: I'm beginning to understand why some heads/head gaskets leak again when relying on a torque spanner, that ultimately does what it wants.... (n)
 
Paul Marx said:
Torque wrenches need to be checked regularly, they wear and age.

Paul
Click to expand...
They sure do. I had a wrench that always seemed a bit on the heavy side. So I borrowed one off a mechanic friend which was calibrated regularly. The difference between mine and the mechanics was startling. I considered writing a conversion chart but in the end I decided I couldn’t trust it and so replaced it.
 
Torque wrenches generally bought by DIY'ers have a far too large range to be precise over the complete range. Somewhere along the line, they may be spot-on, the rest is just a guesstimate... But that isn't too bad, most applications call for EVENLY tightened fasteners, the absolute number is mostly of secondary importance. As long as the shown value is lower than the specified limit for a certain fastener, not much to go wrong. Diffferent if the wrench tightens a lot more than shown.

Wrenches for professional use usually have a quite small working range and rarely a reversable rachet head, ie, work in one direction only. Mechanics working with largely differing fastener sizes need an assortment of torque wrenches. The german "Dreh-mo-meter" wrenches are a nice example. I had my set re-calibrated a couple of years ago, turned out they were on average a mere 1.5% out, after I don't know how many decades.

piet
 
I’ve been using a Britool torque wrench for over 30 years now, After 15 or so years I reckoned it would not be precise anymore, and wanted one with a ratchet and more compact, and bought a Gedore. I compared both by setting same torque figure of 5 kgm (most common setting for a 750 man..🙂) on both wrenches and connecting both wrenches to eachother. If right, both would click at exactly the same time, which they did!
I still use the Britool most of the time..

Think it’s important to always unload the spring after using the wrench.

Marnix
 
I Use teng tool torque tools. I’m happy with their products. I did read this review on amazon for a sliver line torque wrench , which is entirely impressive. Image bought several sets of their spinners to have around the workshop , due to their quality and price I’m really happy. Their lifetime warranty is impressive as well.
here’s the review from Amazon Uk on the torque wrench.



Devan
5.0 out of 5 starsVerified Purchase
Accuracy Tested Using a Torque Wrench Calibrator, Excellent Value and a Lifetime Guarantee + Adapter & Extension
Reviewed in the United Kingdom on 6 February 2014
Size Name: 28 - 210 Nm, 1/2 inchStyle Name: 1/2" Torque Wrench
I bought this item based on the excellent reviews, but wasn't expecting too much wow.

First of all it comes well packaged in a sturdy case. Included is a 1/2" to 3/8" adaptor (very handy) and a 100mm long 1/2" to 1/2" extension. The finish of the chrome vanadium of all parts is excellent and the wrench operates with a smooth and sturdy quality.

Despite all the good news upon inspection I still wasn't convinced, I needed objective results. Working for Delphi, a large automotive parts design/manufacturing company I popped over to one of the labs and pulled out the torque wrench calibrator, a Norbar Pro-Test Series 2 [...] costing approx £2000.

And these are the results, the first number is the indicated reading and the second number the measured value.
28 Nm - 28.8 Nm
42 Nm - 41.8 Nm
56 Nm - 57.2 Nm
70 Nm - 70.3 Nm
84 Nm - 85.1 Nm
98 Nm - 97.6 Nm
112 Nm - 114 Nm
126 Nm - 127.2 Nm
140 Nm - 142.1 Nm
154 Nm - 155.9 Nm
168 Nm - 168.3 Nm
182 Nm - 184.8 Nm
196 Nm - 196.3 Nm
210 Nm - 209.7Nm

Now I must admit, every time I tested it at a different setting the figures would vary slightly. The above values are an average of three tests at each setting.

Most torque values given in a Haynes book have a range of plus or minus 10%. This tells you there's a safety factor designed into most fasteners. Torque is a method of tensioning a bolt to give an axial load (basically the tension it creates to hold two or more parts together). Now there are a few variables that can affect the axial load of a screw threaded fastener for any given torque value. Namely variations in friction between the male and female thread and the underside of the bolt head and fixing face. If you're after a high level of axial load accuracy then you should be using a torque and angle method. This is where an initial torque is applied to fix the mating parts together and a rotation through a set angle of say 80 degrees gives the required axial load. This greatly reduces variations resulting from changes in the coefficient of friction between the threads, caused by lubrication or lack of and even rust. These methods are often used on an assembly line for torque critical items such as high pressure diesel injection system fuel pipes.

In summary the home/garage user really doesn't need to invest in overly expensive torque equipment. Assuming it lasts and continues to give relatively accurate results, this device is more than capable. It's best to store the item at the lowest torque setting as this prevents the spring from 'creeping' and stretching. DO NOT be tempted to set it more than half a turn below its minimum setting as this may just disengage it from the thread causing damage.

So an excellent purchase and if you register it at Silverline's website using the product code 633567 (which is not obvious to find on the box) it is guaranteed forever!

Well done Silverline, you really have marketed/manufactured an excellent product.
684 people found this helpful

so anyone wanting an economic option could get one of these.
 
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sfcpiet said:
Torque wrenches generally bought by DIY'ers have a far too large range to be precise over the complete range. Somewhere along the line, they may be spot-on, the rest is just a guesstimate... But that isn't too bad, most applications call for EVENLY tightened fasteners, the absolute number is mostly of secondary importance. As long as the shown value is lower than the specified limit for a certain fastener, not much to go wrong. Diffferent if the wrench tightens a lot more than shown.

Wrenches for professional use usually have a quite small working range and rarely a reversable rachet head, ie, work in one direction only. Mechanics working with largely differing fastener sizes need an assortment of torque wrenches. The german "Dreh-mo-meter" wrenches are a nice example. I had my set re-calibrated a couple of years ago, turned out they were on average a mere 1.5% out, after I don't know how many decades.

piet
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The comment with the small working range made me think, as well as your comment about they are spot on in one segment but not in others probably. this is exactly what I saw... If you try to adjust them, you just change the area they are spot on.

what puzzled me the most is the difference between the first and all following clicks. Maybe I am simply to paranoid about it. When I fastened the cylinder head the last time, I was thinking that the second screw was not giving the same resistance as the first one. I set the torque wrench 2 Nm higher and - for what reasons ever - this is exactly the difference I measured between the first and all following clicks on that wrench :oops: when I checked the first screw again (untightening it 90° and then tightening it back again), the wrench clicked at the same angle as before. I took that as a sign there was something wrong with this wrench and bought me the measuring tool...

@MarnixSFC: releasing the tension on the torque wrench when finished is something I learned before I first time was allowed to even touche one. ;)
 
I have had two Snap On Torque wrenches for about 40 years, a big one with 1/2" drive for higher torques and a smaller 3/8" one for lower end stuff, both of them have an adjuster similar to a micrometer, both of them came to me at separate times because a professional was buying new Snap on Stuff which has batteries, and give a "your nearly there warning" by vibrating and then they click when bang on, not for me is that, as the batteries would be flat whenever I want to use the things, no doubt they could do with checking, but I don't know how to get that professionally done by someone who is not trying to sell me new kit and is ACTUALLY good at the testing procedure, so they don't get done, I have several quarter drive torque wrench handles that are pre-set and not adjustable, these all came for a few quid from a boot sale, and are 1/4" drive and appear like thick-ish screwdriver handles, all of them are fairly useless as the torque setting are really low (in the inch/pounds) but you never know, I was told they would have been used in a production facility, by someone, no idea who.

I would like to buy two pre-set torque wrenches one at 25ft/lbs and one at 15ft/lbs, they would have to be very high quality
CLEM
 
I've got a couple of Teng torque wrenches. Teng tools appear to be reasonable quality. One is a small 1/4" drive and the other is a bigger one with 3/8" drive. I forget the actual ranges on each of them, but it's something like 30Nm max for the 1/4" and up to 100Nm for the 3/8". They cover most of what I want to do. As a home mechanic, my torque wrenches don't get a lot of use, and I always re-set them to zero when not in use so as to keep the internal spring unloaded. So I expect they'll stay in some sort of calibration long enough to see me out.

For things like the Jesus nut or wheel nuts on the car, I use a rattle gun. I reckon my cheapo Chinese rattle gun would struggle to do much more than 100Nm. As an experimment, I clamped an old 3/4" BSF bolt in the vice, put a nut on it and rattled away at it with 100psi air supply for about a minute to tighten it as much as the tool could manage. I had to stop a couple of times to let the compressor catch up. I dunno what grade the bolt was but didn't appear to be high tensile when I dabbed it against the bench grinder. The rattle gun didn't do anything nasty like shear the bolt off or strip the thread. And I could stull undo the nut with a ring spanner afterwards, although it took a bit of serious grunting and swearing. Conclusion - it's a shit rattle gun. Anyway, I figured if it can't fuck up a beat-up old 3/4" bolt of dubious quality, then it's safe to use on wheel nuts and larger threads.
 
I tend to agree with Piet, that even settings are more important than outright accuracy. I've reassembled the 750 quite a few times without a torque wrench and nothing awry has ever come of it my motors don't leak. I've got a 1/2" drive Warren & Brown (sold through Repco in Oz). I might get it recal'd simply because it's about 40 years old. I reckon it's a top notch unit and it doesn't work of a compressed spring, but a bend in the bar, which clicks off a release pin when the adjuster makes contact with the release plate.

In the bicycle world torque accuracy at very low settings has become critical with the widespread use of carbon fibre in very light gauges. Inch pounds (or grams?) are the go.
 
piranha-bro2 said:
it doesn't work of a compressed spring, but a bend in the bar, which clicks off a release pin when the adjuster makes contact with the release plate.
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I don't reckon there's much that can go wrong with that type. I'd be surprised if its calibration changes.

I still have an old torque wrench that's even less high tech. It just has a scale and a pointer on the handle. The handle deflects as you put force on it and you read off the torque on the scale. It's about as simple as you can get, and it works both ways. I can't imagine how it would ever lose its calibration during normal use.
 

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cape said:
How about this one? At least the torgue is easy to set.
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I thought about such a tool. I am just not really confident it is any more accurate than my existing tools, as these electronic things are sooo cheap...

Saturday, we tested the two torque wrenches of a friend of mine. One was a "no-name" (at least we did not find any brand on it), the other was a roughly 30 - 40 year old Gedore, used by one of his previous employer. The "no-name" was almost accurate around the lower side of the scale (40Nm) but when adjusted to 130Nm, it released only at over 168... As he is only doing the nuts of his wheels with it which need 130Nm, we set it to be accurate around that load and left it there.

The Gedore was - though 30-40 years old and used in a professional workshop - VERY accurate... 10Nm setting, it released at 9,8, 20Nm it released at 19,6 and at 40Nm, it released at 39,8. Also, 4 times clicking it did not change the setting much (withing 0,3Nm up and down on all 3 settings).

This proofs enough for me that this thing is really worth the money... I will bin at least 2 of my 4 torque wrenches and potentially buy me a new one for the range up to 40Nm...
 
Dellortoman said:
I don't reckon there's much that can go wrong with that type. I'd be surprised if its calibration changes.

I still have an old torque wrench that's even less high tech. It just has a scale and a pointer on the handle. The handle deflects as you put force on it and you read off the torque on the scale. It's about as simple as you can get, and it works both ways. I can't imagine how it would ever lose its calibration during normal use.
Click to expand...
I have one of these, too. Need to check it with my device, will report back.
 
will definitely test and report... :)

For those that are unsure and do have lots of screws/nuts to fasten where the right, constant torque counts, I can only recommend to get your wrenches checked or make sure you have a high class one.
 
Wired up some new 12.5MW (12500kW) aeration blower motors at a sewerage treatment plant. The HV terminations were M16 brass nuts on brass studs. The manufacturer specified 110nm. We had two freshly calibrated Kinchrome 1/2” drive torque wrenches. I stopped before the click occurred as it already was so bloody tight I felt I was going to break the stud, in which case I may as well have thrown myself in the shit tank. I tried the other wrench and it hit 110nM well before it got to the point of the previous wrench 🤨
 
rowdypat said:
Wired up some new 12.5MW (12500kW) aeration blower motors at a sewerage treatment plant. The HV terminations were M16 brass nuts on brass studs. The manufacturer specified 110nm. We had two freshly calibrated Kinchrome 1/2” drive torque wrenches. I stopped before the click occurred as it already was so bloody tight I felt I was going to break the stud, in which case I may as well have thrown myself in the shit tank. I tried the other wrench and it hit 110nM well before it got to the point of the previous wrench 🤨
Click to expand...
That is why I bought me the device to test them. Will do that with any torque wrench I ever use. I will even adjust it before using it any time I need to fasten a screw... the results were simply to shocking...
 
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