Proper use of Torque Wrenches

[JayArr]

A torque wrench is only accurate when you apply force at the handle, if you hold your hand farther down towards the socket, it will apply more torque than set for.

Who told you that? I was taught that it didn't matter that it just required more force if I choked up but that the click meant that the set point had been reached. If I set the handle for 99 lbs on a three foot torque wrench I need 33 pounds of force on the end or 50 pounds of force at 2/3 (2 foot) or 99 pounds at 1/3 (1 foot) mark, but no matter what there is 99 foot pounds of force on the nut when it clicks.

If I've been wrong about this there are a lot of misadjusted nuts on my vehicles.

Can someone confirm what GMCMAN posted is true?

 

[Uncleenvoy]

Yeah..doesnt the mechanism sense whatever u set it at and clicks when that amount of pressure is reached no matter how you reach it?i covet one if those digital ones but cant convince myself to pull the trigger and pay those prices. maybe ill go look for one in Craigslist or somwhere

 

[mrrsm]

This kind of information has More Value, depending upon How and Where it is Delivered... Because... One should always...

"Praise in PUBLIC... Criticize in PRIVATE..."

 

[TJBaker57]

Who told you that? I was taught that it didn't matter that it just required more force if I choked up but that the click meant that the set point had been reached. If I set the handle for 99 lbs on a three foot torque wrench I need 33 pounds of force on the end or 50 pounds of force at 2/3 (2 foot) or 99 pounds at 1/3 (1 foot) mark, but no matter what there is 99 foot pounds of force on the nut when it clicks.

If I've been wrong about this there are a lot of misadjusted nuts on my vehicles.

Can someone confirm what GMCMAN posted is true?

I didn't know the answer not knowing how torque wrenches are made. So I did this experiment and there appears to be a difference!! It can be seen that I cannot lift the hanging weight, a vise, from the handle end of the torque wrench but I can lift the vise from a choked up position!

New video by Thomas Baker

photos.app.goo.gl

 

[Uncleenvoy]

All this torque talk just reminded me i forgot to torque the crossmember bolts and trans pan bolts..gotta do that first thing in the morn..thanx guys

 

[TJBaker57]

misadjusted nuts

I resemble that remark!

 

[budwich]

I think you guys are over thinking things a bit. The torque is "set" at the nut by the amount "dialed in" on the handle or otherwise (ie. digital wrench). The amount of torque provided at the nut is the same regardless of where you "hold" the wrench. If you hold it closer then YOU have to provide more torque (effort) to the wrench to cause the result (the same result) as you would holding it at the end. You are the changing effort not the torque at the nut.

 

[TJBaker57]

I think you guys are over thinking things a bit. The torque is "set" at the nut by the amount "dialed in" on the handle or otherwise (ie. digital wrench). The amount of torque provided at the nut is the same regardless of where you "hold" the wrench. If you hold it closer then YOU have to provide more torque (effort) to the wrench to cause the result (the same result) as you would holding it at the end. You are the changing effort not the torque at the nut.

Then why does the wrench in my video click when pressed at the handle but does not click when pressed further up the handle when lifting the very same force (hanging weight)?

 

[budwich]

because you need more force to create the same torque as you move up the handle (towards the tightening nut). It is you (your arm... your weight, whatever) that changes to create SAME torque at the bolt / nut.

Your "test" has no "calibration"... meaning you aren't sure of what force you are putting on the torque wrench. Basically, the "multiplier effect" of the wrench is "more than subtle" at the different points. In one case, just enough to cause the "click" in others, not so much so.

 

[TJBaker57]

because you need more force to create the same torque as you move up the handle (towards the tightening nut). It is you (your arm... your weight, whatever) that changes to create SAME torque at the bolt / nut.

Your "test" has no "calibration"... meaning you aren't sure of what force you are putting on the torque wrench. Basically, the "multiplier effect" of the wrench is "more than subtle" at the different points. In one case, just enough to cause the "click" in others, not so much so.

Well the way I see this test is thus.

I have a hanging weight that does not change, plus a distance from center of rotation that does not change, equalling a rotational force that does not change. A constant which requires no calibration for this purpose.

I then have a torque wrench whose setting does not change. And yet by moving the point where force is applied to the wrench handle the force given to the load does change. A rotational force greater than the wrench setting is applied when my hands move up the handle lifting the hanging weight.

When force is applied at the handle end it results in less force applied to the load and the wrenches setting is properly achieved.

 

[gmcman]

I think you guys are over thinking things a bit. The torque is "set" at the nut by the amount "dialed in" on the handle or otherwise (ie. digital wrench). The amount of torque provided at the nut is the same regardless of where you "hold" the wrench. If you hold it closer then YOU have to provide more torque (effort) to the wrench to cause the result (the same result) as you would holding it at the end. You are the changing effort not the torque at the nut.

I hear what you're saying, and I thought that was the case when I began using them, however that's not how it works.

Think of it this way, and it also plays into your method of thinking....when you have a fastener that requires 50 foot-pounds of torque, you are going to exert 50 pounds on a 1-foot-long handle, or 25 pounds on a 2-foot long handle.

The tool used to set this torque, is calibrated with 50 pounds of force at a set distance, the breakaway force is set after a certain amount of force is being applied to the mechanism.

So if you need 50 foot-pounds of force to tighten the fastener, how much force do you need to apply at a shorter length to achieve that 50 foot-pounds?

It takes more effort (torque) to tighten a fastener using a shorter lever. So on a 24" torque wrench, you would apply 50 pounds. On a 12" wrench, you would apply 100 pounds.

The misconception is the wrench doesn't measure force at the fastener, it measures force applied to the wrench's mechanism.

I believe....I worded that last part correctly..

Edit to add: Think of a beam-style torque wrench, you bend the beam under tightening torque to deflect the indicated value. I'm not versed in the mechanics of the click or digital style wrenches, but it takes more force to change the shape of the beam when choked down on the handle, kinda like a threaded rod, a 4' section bends easily, but a 6" section is hard to bend.

So with a click-style, the head/mechanism is separate from the handle, and by pushing on the handle near the mechanism, you are not allowing the handle portion to deflect as it should. The deflection is imperceivable.

 

[budwich]

OK... but I think I was referring more to the type of torque wrench that tjbaker has in his video where by the mechanism is not a "dual rod / beam" design. As such, that wrench "transfers" the torque from the head thru a "slip contact" (flip) and a spring which "sees" its torque from the entire range of the wrench assuming that the handle itself is not bending. I think a digital head works the same way. The "dual beam" is a different animal and in most cases one would not necessarily normally try to operate it down from the end as you could readily "see" your hand may impact the deflection of the "beam".

The "click style" wrenches may be referred to as "rigid handle"... there is a reason for that, the handle does not deflect. The torque mechanism is based on internal deflection AND "slip / flip" / spring pressure therein.

 

[JayArr]

I hooked my torque wrench up to my digital torque reader and put that in a vise. See pictures.

I set the torque wrench to 50 ftpounds. I set the digital torque reader to 'peak hold'

I torqued against the vise until it clicked, then I read the digital readout.

It didn't matter if I held the torque wrench at the end or half way up my wrench delivered very close to 50 ftpounds of torque at each click.

 

[TJBaker57]

I hooked my torque wrench up to my digital torque reader and put that in a vise. See pictures.

I set the torque wrench to 50 ftpounds. I set the digital torque reader to 'peak hold'

I torqued against the vise until it clicked, then I read the digital readout.

It didn't matter if I held the torque wrench at the end or half way up my wrench delivered very close to 50 ftpounds of torque at each click.

I expect that it depends greatly on the specific construction of the torque wrench. Perhaps higher quality units are more uniform than low-cost chain-store units.

I have yet to see any manufacturers instructions which recommend applying force anywhere but the handle.

Some years ago I had a torque wrench come apart and had the opportunity to see its construction. Alas I do not remember anything specific but do remember there being a recognizeable means for adjustment/calibration.

 

[budwich]

I hooked my torque wrench up to my digital torque reader and put that in a vise. See pictures.

I set the torque wrench to 50 ftpounds. I set the digital torque reader to 'peak hold'

I torqued against the vise until it clicked, then I read the digital readout.

It didn't matter if I held the torque wrench at the end or half way up my wrench delivered very close to 50 ftpounds of torque at each click.

View attachment 98916View attachment 98917

This is as expected. If you look at the design of a "non-digital" (cheaper) rigid "clicker", the reliance of the "internal deflector" and the "slip/flip" mechanism which lies on friction / break point is very "non-linear" towards its "peak".... much like inertia to get some thing moving which takes that little bit to break thru that point. Tjbakers "demo" shows how easy it is to have or not have that "break point"... his further relies on other "frictions" across the setup which will impact the outcome. The "published accuracy" of the clickers is something like 6%... that's if properly calibrated which I doubt the average DIY tooler ever does / maintains. It would quite easily move the accuracy of the "break" to 10% or higher which again taking into account "multiplier effect" of an "uncontrolled hand" at various points makes his "demo" some what.... well ... hmmm.

 

[gmcman]

The "click style" wrenches may be referred to as "rigid handle"... there is a reason for that, the handle does not deflect. The torque mechanism is based on internal deflection AND "slip / flip" / spring pressure therein

Correct, the head/mechanism is separate from the handle, the deflection I was referring to was the handle to the seperate mechanism.

Just for clarification I'm not saying the wrench will be off by 50% using it halfway down the handle, just an example it takes that much effort on your part.

Here's a good video on this topic.

Disclaimer: This is not directed anyone here..lol, he seems a bit salty and obviously towards his own viewers or something else.

But it shows how the values change. What was surprising is the value changed by almost 25% when choking down on the handle.

 

[budwich]

Interesting... but I think you could get a similar degree of "variance" by holding the handle at the same place and varying the force (ma) along the way (ie. less smooth, more abrupt, slower, etc) just do the "slip / flip" design of the "break" which is kind of what he shows in the video.

 

[JayArr]

Well this certainly has my attention. I decided to dismantle my older torque wrench to see how it works. Take a look at the pictures.

The click is heard when the torque on the outer casing acting against the resistance of the bolt causes the little metal rectangle to 'roll' and allow the half shaft to hit the outside casing.

I still don't know why he gets different readings as he moves his hand up and down the shaft, According to physics and Archimedes (for the last 2000 years) it shouldn't matter where on the outer shaft the force is applied. It's a lever with a fulcrum.

The only thing that changes is the speed at which the force is applied. With a long lever the force is applied slowly as the handle is swung through a longer arc. I wonder if instead of a human arm we used a screw to push the wrench if we would get the same results. If we varied the speed that the force is applied to compensate for where on the shaft we were applying it would that even it out?

The pragmatic end of things is that the spring/scale is designed to be accurate only when your hand is on the handle in the proper location.

This means there are a bunch of crank bolts in various engines that I put on with pipes on the end of my wrench that are under-torqued.

 

[JayArr]

OK, new test! And I think I may be onto something.

I'm still set for 35 ftlbs on the torque wrench and attached to the vice.

I went and got my scale for weighing my suitcase when I travel. I'll admit it's probably not well calibrated but it does come with a needle to capture the peak weight.

I put it around the handle and keeping it at 90 degrees to the wrench I apply pressure SLOWLY. At the click the weigh scale reads 23 pounds. The digital meter reads 34.8. It's 18" from the end of the wrench so that's pretty good. (23*1.5=34.5)

Next I place the weigh scale half way up the shaft (approx 9") and pull. The first few times I get readings of 55-56 pounds on the weigh scale and 39-40 on the digital scale. Except that once or twice my digital guage reads overload??

Then I do it slowly and notice an anomaly. I can count off the readings on the dial but when it clicks the weigh scale jumps forward several pounds. ie: counting 45, 46, 47, click - peak reading = 50. The click itself is causing a final jump.

So I do it again but very very slowly this time, I take my time and sure enough if I'm gentle it clicks at 46.

The fact that it clicks at 23 on the handle and 46 half way up the shaft tell me it doesn't matter where the force is applied. If you choke up by half then you need twice as many pounds but it still clicks when it gets to 35ftlbs either way.

I think the digital torque meters are too sensitive for the jolt that occurs as the wrench clicks and they give false readings caused by the half shaft slamming into the outer shell as the square rolls.

I think the more accurate way to calibrate will be to count off the readings BEFORE the click and take the last stable reading as correct (or add 1 pound if you like) that way the error caused by the force of the click is ignored.

 

[gmcman]

Very cool pics @JayArr , thanks.

I guess there is an angular component to this I'm not sure how to describe in regards to being factual.

If you were to lay the torque wrench on the table and push on it about an inch from the head, the whole wrench would slide. However if you were to just push on it from the handle it would rotate near the head.

Also, Given the fact the torque wrench will pivot near the mechanism, that far end of the wrench (the very end of the bar) is going move in the opposite direction of the handle. So I guess when you're pushing on it further up closer to the pivot point, you aren't fully trying to rotate around a pivot point, but pressing more into the pivot point.

 

[JayArr]

The distance from the pivot point doesn't change the math of the forces, that's just basic trigonometry (Sin, Cos, Tan). If the socket is anchored the math is the same no matter where you are on the shaft.

I think what I would have like to have seen on that fancy Snap On machine is it set up to not hold the peak. I wonder if you slowly increased pressure until it clicked and then maintained the force after the click if it would read 35 or 36? and then slowly release to see at what torque it clicks back. I think the sensitivity of the electronics and the force of the click (releasing tension) causes the peak hold readings to be false.

One other thing that changes, but only slightly, is the pivot point. Before the click the pivot point is the center of the nub that the socket goes on, basically the center of bolt. When it clicks the outer shell pivots on the little pin that goes through it and the half shaft so the pivot point moves out about an inch or so. It's getting late so I can't figure out if that's important or what effect it has.

 

[gmcman]

Just to clarify, the little pin is the area I was referring to. If you push on the bar where the pin is, I want to speculate you won't get any feedback when torque is reached. So by that rarionale, from the pin to the handle, there has to be some type of progression, or "regression" of values.

So my understanding is, when you apply force near the pin, or halfway up the shaft, you are not just applying force to the handle to overcome the tension where the pivot is, but also applying force into the pivot pin. This difference in force is what the machine is registering.

This is a good "tangent" to a thread as it's a learning curve and I'm surely learning from it.

 

[Uncleenvoy]

@JayArr what kind of torque adapter do you have? I currently have two regular click type torque wrenches..a large one that does 10 ft lbs to 150 i think , and a small one for inches/ft..cant remember the range..i want to get an adapter that can switch back and forth to from ft/lb to inch/ft with a decent range..some ive seen only goes up to 99 ft/lb..ive been lazily looking for one but havent really done a serious search for one

 

[mrrsm]

FelPro has assembled some remarkable On Topic information within this PDF on Torqueing Engine Head Bolts along with a vast array of what their procedures are supposed to be by Manufacturers, Makes and Engine Models:

 

[JayArr]

Hi Uncleenvoy I've got the same as you, one smaller one for inch pounds and a big one for ft pounds. I've never seen a torque wrench that can do the whole range fron inch pounds to foot pounds.

The big one maxes out at 200 so I bought the little digital box to torque head bolts and crank bolts and other high torque stuff. you can set it for a particular torque and it will let you know as you get close to the set point. The beeps get closer and closer together as you approach the set point and it goes to a solid tone when you hit the set point. It's handy for torquing a crank bolt to 250 ftlbs with a 6 foot plumbers pipe on the end of your 2 foot breaker bar.