Interesting discussion of course. But what I can tell you is EVERY single fastener that I use where torque actually matters in a critical way (think things like rod bolts and engine heads and hydraulic cylinders, etc.) the actual condition of the fastener IS listed as part of the torque specification (wet, dry, oil, whatever). and I follow those religiously. Now when I get to fasteners on my truck/dozer/tractor that simply really don't matter (if its not a graded bolt in a critical area that's like 99.999% of the time) I do add antiseize to make it easier the next time given I live in a terrible area for corrosion (seacoast) and torque to the called for torque even if I know that's not 100% correct. Because for these fasteners it won't really matter. I feel better because I used a certified torque wrench but the practical difference to my just tightening it is probably nearly none.

What torque is not: bolt tightness.

What torque is: bolt stretch.

Yes, wet torque is a thing, and it's a critical thing. If you're not using the correct torque specifications, why bother torquing at all? Why not just guess.

Torque is used for two primary reasons: even tightness between two surfaces that are secured with a rotating fastener (eg, bolt or screw), and protecting the fastener from failure.

then a fastener is run into a threaded hole and tightened, the fastener is stretched: specifically, the stretching and tension is between the fastener head, and the threads. There is a tension stretching, and a torsion. Both can lead to failure of the fastener.

When multiple bolts are installed in a surface, often there is a specific tightening pattern that must be used. The reason for that is to reduce stresses on the parts and to ensure that there is equal, even compression between them, applied by the fasteners. The consequence of failing to follow the correct order and torque is a warped head, or failed wheel half, or component. One overtightened component takes the load and means the opposing fasteners on the other side of the surface are not tight enough, even when one is overtightened.

Use dry torque where dry fasters are installed, and wet torque where it's applicable, but don't use wet torque values on dry components, and visa versa. Using dry torque values on wet installations can lead to fastener failure, excess load on the fastener, unequal and uneven surface compression, and part failure. Use the correct, parts, correct tools, and the correct numbers.

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Originally posted by sns3guppy:
What torque is not: bolt tightness.

Well it kinda is isn't it? Wouldn't a lug nut tightened to 70 ft lb be tighter than one tightened to 15 ft lb?

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Torque is used for two primary reasons: even tightness between two surfaces that are secured with a rotating fastener (eg, bolt or screw), and protecting the fastener from failure.

I don't know but to me protecting an alloy engine component is far more important than the bolt that's being tightened in to it.

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a fastener is run into a threaded hole and tightened, the fastener is stretched:

Or the threads in the hole are stretched..... or stripped.

This message has been edited. Last edited by: ridewv,

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Originally posted by ridewv:

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Originally posted by sns3guppy:
What torque is not: bolt tightness.

Well it kinda is isn't it? Wouldn't a lug nut tightened to 70 ft lb be tighter than one tightened to 15 ft lb?

It depends. Instead of tightness, let's think about clamping force, or the amount of pressure the nut is placing on the rim pulling the rim to the hub, which would be equal to the amount of force pulling on the stud in an attempt to stretch it. That's that for every action there's an equal and opposite reaction thing.

Two scenarios:

One, the threads of the stud and lug nut are clean and dry. Torquing the nut to 70 ftlbs will result in X amount of clamping force.

Two, the threads of the stud and lug nut are clean, but lubricated with a miracle lubricant that reduces friction to 0. Because friction is 0, we can turn the lug nut with our fingers the same number of turns we did in the first scenario to generate the exact same amount of clamping force even though the torque is 0. In fact, with 0 friction, we could keep turning the lug nut with our fingers until the stud broke or the threads failed.

In other words, the amount of clamping force is solely determined the number of turns of the nut on the stud and the force of torque on the nut is solely overcoming friction. The less friction, the less torque for the same amount of clamping force.

You could probably prove this with a C-clamp and a piece of 2x4. Take the C-clamp and spray with some brake cleaner to get the threads all clean. Clamp it on the 2x4 as tight as you can by hand. Take the C-clamp off. Lubricate the threads with the slipperiest oil you have and clamp it on the same 2x4 in a different spot. Again, tighten it by hand as tight as you can.

I bet the lubricated clamp leaves the deepest impression in the wood. The clamp is the same, the wood is the same, the amount of torque you can apply by hand is the same, and the only difference is the amount of friction. This would prove the inverse relationship between friction of the threads and clamping force.

My high school science teacher was really disppointed that I became an accountant.

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Originally posted by ridewv:
Well it kinda is isn't it? Wouldn't a lug nut tightened to 70 ft lb be tighter than one tightened to 15 ft lb?

A lug nut with an applied torque value of 70 ft-lbs will have higher neck stretch or tension on the lug bolt than a lug nut torqued to 15 ft-lbs. We think in terms of tightness because more force is needed to put the lug nut on, and to remove it. The reality is that the lug bolt is being stretched. Increase the torque value, increase the stretch on that bolt. The resistance is friction on the threads and bearing surfaces, but that friction, in turn, is tension as the lug bolt is stretched.

Too little lug bolt tension means too little friction, and there is a point at which the nut simply won't stay put. There also comes a point at which the tension is insufficient, meaning the clamping force is insufficient; if it's unequal on opposing sides of the wheel, it also affects the clamping force across the wheel, and around the wheel: it affects the ability of the other lug bolts to do their job, and consequently the tension on those bolts. Too loose the load falls on the opposing bolt. On some parts, like an aluminum cylinder head, this may lead to warping or failure of the opposing side as the opposing side takes the load. In other cases it may cause loss of tension on other bolts.

It's all about fastener tension, however. We think of torque as tightness. It's not. It's fastener tension, and becasue it's impractical to to measure fastener elasticity and stretch, it's the closest we can approximate with a simple, calibrated hand tool.

Think of it this way: torque values change with the size of the fastener. A bolt, screw, or stud will have a higher torque value if it has a larger diameter. It will have a lower torque value if it has a smaller diameter. A reference to standard torque value charts will show this: standard values are based on the size of the shaft, for a given fastener material.

In context of the thread, when applying torque to a lubricated fastener (eg, wet torque value), the fastener will turn further, with higher fastener tension or stretch, for a given torque value, when wet. Remembering that the torque we experience with the ratchet handle or torque wrench is the force required to rotate the fastener based on bearing surface friction (caused by tension of the fastener being stretched): less friction means we can turn it further, with more stretch or tension, before we reach a given torque value.

If torquing to maximum values with a dry torque, for a given fastener size, we can exceed the capability of the the fastener if the threads are wet. That may mean permanent deformation of the fastener, or failure (such as twisting off a stud, stripping threads, or snapping a bolt. We've reached the limits of elasticity of the fastener, given it's diameter, and material. We may also exceed the capability of the material being fastened or clamped: the limiting factor may be aluminum threads being fastened with a steel bolt, for example. The cause is the same: excess fastener tension, causing excess friction, causing failure of the fastener or part. Hence, manufacturer or standard torque values that are recommended or required.

Insufficient claimping force may mean a failed part, too; Clamping force on one area of a part is affected by the fasteners on other areas of the part (which is part of the reason that we do initial torque application on opposing bolts on a surface such as a wheel or cylinder head).

The problem we have is that while you can apply identical torque values using a calibrated wrench (the best we can do with hand tools in a realistic setting), the actual clamping force applied will vary, sometimes significantly. That may be due to lubrication on the threads. It may be due to an odl bolt and a new bolt on the same part or surface. It may be due to flex in the surface material, or torquing (clamping) in the wrong order. Where torquing is required in a particular pattern, for example, failure to follow that pattern will produce inaccurate clamping force, despite the the torque wrench clicking to the same value. We think we've torqued it to a given value, but failure to do it in the correct pattern or order means we haven't, and the effect can lead to failure of fasteners or the part itself.

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Originally posted by trapper189:

....Two scenarios:

One, the threads of the stud and lug nut are clean and dry. Torquing the nut to 70 ftlbs will result in X amount of clamping force.

Two, the threads of the stud and lug nut are clean, but lubricated with a miracle lubricant that reduces friction to 0. Because friction is 0, we can turn the lug nut with our fingers the same number of turns we did in the first scenario to generate the exact same amount of clamping force even though the torque is 0. In fact, with 0 friction, we could keep turning the lug nut with our fingers until the stud broke or the threads failed......

Miracle lubricant may eliminate the friction between external threads on the stud and the internal threads in the lug nut but there will still be clamping force from either stud stretch or thread deform applied which will require torque which you wouldn't be able to do with your fingers. At least I couldn't.

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Miracle lubricant may eliminate the friction between external threads on the stud and the internal threads in the lug nut but there will still be clamping force from either stud stretch or thread deform applied which will require torque which you wouldn't be able to do with your fingers. At least I couldn't.

I use anti-seize on many things but lug nuts isn't one of them.
I follow the recommended procedure and torque them dry if that's what it calls for.
You may be popping them at torque specs but you can stretch the studs beyond what they are rated for.
I've seen enough wheel end failures that I just follow the specs myself.

I have some Detroit Diesel peanut butter for head bolts that if it were to be used on a lug nut it would most likely snap off before you popped it at 80 ft lbs.

With the features that torque wrenches have today you can measure torque and angle at the same time.
Set up a couple fasteners dry and wet.
Pre-load each then pop them to spec noting how many degrees each turned.
Not exactly scientific but can give an estimate on how much more one turned to get to the same torque spec.

I use that feature to spot failing hardware.
Take rocker shaft bolts for example.
Spec is 20 ft lbs then 120 deg which is about 70 ft lbs for new bolts, with a 3 use life.
Serviceable bolts start from 20 ft lbs and increase in torque to about 70 ftlbs.
Bolts that have been reused too many times will start out at 20 hit about 45 ftlbs then drop off to 30 or so at 120 degrees.
Snapping off a rocker shaft bolt down inside a cam cap is bad enough, which is what happens to the new guys occasionally. .
Sending it down the road and having the bolts fail while under a load is a bad day.