Recommend Me a Torque Wrench Please

[Airsporter1st]

I feel a bit guilty because I may have first mentioned 'zero'. In fact many wrenches say to turn the adjustment down to the minimum rated value in the instructions, eg here;

https://www.tekton.com/manuals/manual_24340.pdf

where 25ftlbs is the minimum value.

At this point there is still a fair amount of load on the knuckle inside the wrench so parts are not going to move or come adrift. In theory, in most cases it ought to still be OK at a genuine zero, i.e. the knuckle should not be loose inside, but if you stray past zero into a negative setting then pretty much anything can happen.

The chances of something bad happening and the nature of it vary with the exact design of the wrench; the one in the manual above is a fairly common design, but there are many possible variations. IIRC in the design above the knuckle ('roller bearing' part) may rotate when there isn't enough load on it and this can throw the wrench completely out of whack. in other apparently similar designs the part that bears against the knuckle either itself turns or doesn't and this changes the chances of something bad happening unless the knuckle is actually loose inside. In others the knuckle works against a pin that can come out of position and again the wrench cannot work once this has happened.

Being able to carry out some kind of rudimentary check on the calibration of clicker wrenches is a very useful thing to be able to do.

cheers

My point exactly. My torque wrenches don't have a marking of 'zero' or 0 of any sort at all. The markings stop at their lowest rated value for each wrench. So if I continue to turn down attempting to find 'zero' I won't, so perhaps I'll just guess and probably guess wrong. With whatever consequences. This is what I've done with mine, IIRC. Teng, in one of their web pages, also say 'zero'. The printed instructions say minimum. I'll alert them to the ambiguity. This is partly my fault for not reading the instructions with enough care. But at least this discussion has clarified the issue for me.

Casual or colloquial use of language which has actual technical meaning is frequently understood to be colloquial. And may well be acceptable, depending on context. So two friends discussing a recent illness and describing it as "chronic" or "acute" might very well just mean "really bad". If one of them is a medical practitioner you would expect her to perhaps clarify the meaning. And if they are BOTH medical practitioners, and at work, you would hope that they would use those terms with their exact medical meaning. I suppose "plethora" might be a better example.

In the context of this discussion, it is quite possible that two experienced mechanics working together might say, when one borrows the other's torque wrench - "remember to zero it when you've finished Pete". It may be incorrect (depending on manufacturer's instructions), but hopefully they would understand each other. Although the arrogance of surety that experience and qualifications bring is as equally distributed amongst the manual trades as it is amongst the professions, in my experience. Fortunately we musicians have the binary reminder of our imperfection, the wrong note, which quickly corrects any mistaken self-image of perfection we have adopted.

But when one is giving advice to someone who it is assumed has less knowledge or experience of a subject than oneself, then the wise course is to adopt their perspective. I know that "the bottom string" of the guitar means the lowest sounding. So do my fellow guitarists and most players of other instruments would understand. But several times each day I have to remind my students that the "bottom string" is actually the one furthest away from the ground. So I try to use language precisely, and clarify if necessary.

OP, if you buy a torque wrench, get a good one and read the manufacturer's instructions for its care.

.....and. there endeth today's sermon - hopefully.

[mikeymo]

I feel a bit guilty because I may have first mentioned 'zero'. In fact many wrenches say to turn the adjustment down to the minimum rated value in the instructions, eg here;

https://www.tekton.com/manuals/manual_24340.pdf

where 25ftlbs is the minimum value.

At this point there is still a fair amount of load on the knuckle inside the wrench so parts are not going to move or come adrift. In theory, in most cases it ought to still be OK at a genuine zero, i.e. the knuckle should not be loose inside, but if you stray past zero into a negative setting then pretty much anything can happen.

The chances of something bad happening and the nature of it vary with the exact design of the wrench; the one in the manual above is a fairly common design, but there are many possible variations. IIRC in the design above the knuckle ('roller bearing' part) may rotate when there isn't enough load on it and this can throw the wrench completely out of whack. in other apparently similar designs the part that bears against the knuckle either itself turns or doesn't and this changes the chances of something bad happening unless the knuckle is actually loose inside. In others the knuckle works against a pin that can come out of position and again the wrench cannot work once this has happened.

Being able to carry out some kind of rudimentary check on the calibration of clicker wrenches is a very useful thing to be able to do.

cheers

My point exactly. My torque wrenches don't have a marking of 'zero' or 0 of any sort at all. The markings stop at their lowest rated value for each wrench. So if I continue to turn down attempting to find 'zero' I won't, so perhaps I'll just guess and probably guess wrong. With whatever consequences. This is what I've done with mine, IIRC. Teng, in one of their web pages, also say 'zero'. The printed instructions say minimum. I'll alert them to the ambiguity. This is partly my fault for not reading the instructions with enough care. But at least this discussion has clarified the issue for me.

Casual or colloquial use of language which has actual technical meaning is frequently understood to be colloquial. And may well be acceptable, depending on context. So two friends discussing a recent illness and describing it as "chronic" or "acute" might very well just mean "really bad". If one of them is a medical practitioner you would expect her to perhaps clarify the meaning. And if they are BOTH medical practitioners, and at work, you would hope that they would use those terms with their exact medical meaning. I suppose "plethora" might be a better example.

In the context of this discussion, it is quite possible that two experienced mechanics working together might say, when one borrows the other's torque wrench - "remember to zero it when you've finished Pete". It may be incorrect (depending on manufacturer's instructions), but hopefully they would understand each other. Although the arrogance of surety that experience and qualifications bring is as equally distributed amongst the manual trades as it is amongst the professions, in my experience. Fortunately we musicians have the binary reminder of our imperfection, the wrong note, which quickly corrects any mistaken self-image of perfection we have adopted.

But when one is giving advice to someone who it is assumed has less knowledge or experience of a subject than oneself, then the wise course is to adopt their perspective. I know that "the bottom string" of the guitar means the lowest sounding. So do my fellow guitarists and most players of other instruments would understand. But several times each day I have to remind my students that the "bottom string" is actually the one furthest away from the ground. So I try to use language precisely, and clarify if necessary.

OP, if you buy a torque wrench, get a good one and read the manufacturer's instructions for its care.

.....and. there endeth today's sermon - hopefully.

Well, you didn't have to read it. Or to reply. But apparently you couldn't resist the temptation of a sarcastic reply with no content. Well done.

[Gattonero]

I think there is somewhat a myth about "setting the torque wrench to zero after use".
My latest tool is a precision WIHA torque screwdriver that is calibrated from 1 to 6Nm, an expensive tool that I bought new. Since new, I have compared it to a Beta 1/4" and a Premier 3/8" torque wrenches that had both been calibrated a long time ago and never get reset to their minimum value.
Guess what? On a bunch of different fasteners, both the old wrenches would show less than 10% difference on a 5Nm torque test.
I suppose this has to do with the materials and size of the internal spring and the thread to adjust the wrench, they're not all the same.

[Airsporter1st]

My point exactly. My torque wrenches don't have a marking of 'zero' or 0 of any sort at all. The markings stop at their lowest rated value for each wrench. So if I continue to turn down attempting to find 'zero' I won't, so perhaps I'll just guess and probably guess wrong. With whatever consequences. This is what I've done with mine, IIRC. Teng, in one of their web pages, also say 'zero'. The printed instructions say minimum. I'll alert them to the ambiguity. This is partly my fault for not reading the instructions with enough care. But at least this discussion has clarified the issue for me.

Casual or colloquial use of language which has actual technical meaning is frequently understood to be colloquial. And may well be acceptable, depending on context. So two friends discussing a recent illness and describing it as "chronic" or "acute" might very well just mean "really bad". If one of them is a medical practitioner you would expect her to perhaps clarify the meaning. And if they are BOTH medical practitioners, and at work, you would hope that they would use those terms with their exact medical meaning. I suppose "plethora" might be a better example.

In the context of this discussion, it is quite possible that two experienced mechanics working together might say, when one borrows the other's torque wrench - "remember to zero it when you've finished Pete". It may be incorrect (depending on manufacturer's instructions), but hopefully they would understand each other. Although the arrogance of surety that experience and qualifications bring is as equally distributed amongst the manual trades as it is amongst the professions, in my experience. Fortunately we musicians have the binary reminder of our imperfection, the wrong note, which quickly corrects any mistaken self-image of perfection we have adopted.

But when one is giving advice to someone who it is assumed has less knowledge or experience of a subject than oneself, then the wise course is to adopt their perspective. I know that "the bottom string" of the guitar means the lowest sounding. So do my fellow guitarists and most players of other instruments would understand. But several times each day I have to remind my students that the "bottom string" is actually the one furthest away from the ground. So I try to use language precisely, and clarify if necessary.

OP, if you buy a torque wrench, get a good one and read the manufacturer's instructions for its care.

.....and. there endeth today's sermon - hopefully.

Well, you didn't have to read it. Or to reply. But apparently you couldn't resist the temptation of a sarcastic reply with no content. Well done.

.....and you couldn't resist the temptation of jumping up on your soapbox and preaching, when all I was trying to do was be helpful.

[Airsporter1st]

I think there is somewhat a myth about "setting the torque wrench to zero after use".
My latest tool is a precision WIHA torque screwdriver that is calibrated from 1 to 6Nm, an expensive tool that I bought new. Since new, I have compared it to a Beta 1/4" and a Premier 3/8" torque wrenches that had both been calibrated a long time ago and never get reset to their minimum value.
Guess what? On a bunch of different fasteners, both the old wrenches would show less than 10% difference on a 5Nm torque test.
I suppose this has to do with the materials and size of the internal spring and the thread to adjust the wrench, they're not all the same.

Yes, I also have an adjustable torque screwdriver which has remained at its set torque for years and yet doesn't appear to need recalibration. I wonder whether these types have a different mechanism from the beam-type clicker wrenches? From experience in other uses, I would definitely say that the quality of the spring has a big part to play.

[mikeymo]

I think there is somewhat a myth about "setting the torque wrench to zero after use".
My latest tool is a precision WIHA torque screwdriver that is calibrated from 1 to 6Nm, an expensive tool that I bought new. Since new, I have compared it to a Beta 1/4" and a Premier 3/8" torque wrenches that had both been calibrated a long time ago and never get reset to their minimum value.
Guess what? On a bunch of different fasteners, both the old wrenches would show less than 10% difference on a 5Nm torque test.
I suppose this has to do with the materials and size of the internal spring and the thread to adjust the wrench, they're not all the same.

Yes indeed. Even the thickness of the graduation marks is enough to make a slight difference, perhaps. And the tools you mention, all being quality tools, are presumably designed to last longer under usage or long term storage. Whether "correctly" stored or not. Quality will out I suppose.

I'm slightly more worried that in attempting to set to zero/minimum I've actually gone too far with my torque wrenches and maybe disengaged some of the internal workings. Having found that professional calibration is actually a bit more expensive than I thought, I'll probably do the "weight dangling off the handle" method to check, and only take them to a professional if they appear to be a seriously out.

[Brucey]

I think the quality of the spring makes a big difference too. One of the ways in which a high spring preload puts the wrench out of calibration (at least for the first few clicks after storage, if not longer) is that the pressure in the assembly forces lubricant out of the places where it is needed, or worse yet causes it to separate so that what is left is more like plasticene in its consistency. As I mentioned upthread there are numerous variations on the theme of clicker design. Just looking at the various patents in this field shows this quite well. They don't all work or respond the same way.

But the clicker wrench design I linked to above is one of the more commonplace types; it usually gives a total range of ~x10 with a 4% accuracy and permits the mechanism to have separate adjustments that mostly influence the high and low ranges

By contrast a torque screwdriver (say) often has a simpler torque-limiting clutch in it, that simply 'gives' when the set torque is reached. This normally consists of a spring-preloaded roller (or rollers) that sit in a notched wheel of some kind. A similar (uncalibrated) mechanism is often used in cordless drills so that screws can be driven without being overtorqued. In a calibrated form, the available range (within which there is tolerable accuracy) is usually somewhat less than with a clicker, and once the mechanism is worn, the linearity of the adjustment is usually lost. Note that repeat clicks with such a tool (eg simply turning the tool so that it clicks again and again) usually imparts a shock load to the fastener that may be somewhat in excess of the stated torque. You can see this if you (say) allow a cordless drill to overrun the clutch repeatedly; the fastener goes up a little more. I think you would lose patience with a hand tool before a similar thing would occur.

In aviation use where repeat work is required, such screwdrivers are often 'set' for a particular torque value, regularly checked (daily or better) and the adjuster itself is blanked off with a cover that needs a tool for access. Colour coding (or similar) is used to identify the tool easily.

In general the most accurate and reliable mechanisms separate the high load parts of the mechanism from the adjustment/clicking part of the mechanism. The screwdriver/drill type clutch doesn't do that very well and the standard clicker design only does it to an extent; the lever inside the wrench isn't that long. There are some alternative designs, for example

- the so called 'split beam' torque wrench is a bit like a standard beam wrench but has a short flexure and the deflection in this beam is made high travel/low force via a system of levers. There is an audible click at a set torque value but there is no slippage in the wrench and no impulse torque. There is no great force in the clicking mechanism so it is easier to design a mechanism that stays in calibration even if the dial is not wound down for storage.

- Gedore have for many years made a wrench that looks and works superficially like a standard clicker, but is actually a fair bit cleverer than that. A daisy chain of levers inside the wrench handle transmit the torque loads (with low friction) through to a low-force clicker mechanism, with similar advantages as described above.

However I note that it didn't stop Gedore from buying another company (specialising in torque wrenches of different designs) outright.

- wrenches of this design ('torque meter' etc)

have been made for many years and have a simple mechanism inside that cannot be left at a wrong/high setting. A single coil spring takes the torque load, and the primary adjustment is the end stop on that spring; even if the spring changes slightly in length (through wear etc) it cannot change in stiffness unless it actually cracks. The torque is indicated by a micrometer dial which simply measures the deflection in the spring. I have one of these wrenches and even though it is about sixty years old it is still one of the most accurate tools I own. Unlike clicker wrenches there is almost no part of the wrench that can suffer from high friction and thus throw the calibration out.

So there are many ways of skinning a cat for sure. But be aware that if you get fussy about your torque wrenches, the costs can be eye-watering. The new price of any of the three above can make the cost of a Snap-On wrench look 'pretty reasonable'.....

cheers

[Airsporter1st]

Its been a while since I last bought a torque wrench, but if I was getting one today, I'd buy a digital torque adapter, similar to this one:

https://www.sbvtools.com/en/accessories/137-sbv-digital-torque-adaptor-5425030522950.html

I think I'm right in saying that these use a load cell, which removes any concerns about springs losing their temper, hardening/drying of lubricant or internal component wear. No doubt they have their own limitations and as with most, you get what you pay for, so the cheaper models might not be so great. The one linked has a tolerance of 2% and a good range.

P.S. Some of these also incorporate an angle gauge, which is often required for e.g automotive cylinder head tightening.

[Brucey]

that looks like a nice thing; I'd want to keep it indoors in the warm and dry, not in the cold and damp of my workshop though.

cheers

[Airsporter1st]

that looks like a nice thing; I'd want to keep it indoors in the warm and dry, not in the cold and damp of my workshop though.

cheers

Some of the better makes e.g. Sealey, Facom and many others are made for the workshop environment, so I'd expect them to be OK. Some of the cheaper ones may not be as robust or well sealed, though, in which case keeping in the warm and dry would probably be a wise idea.