That's true of course (levers are so cool!), so as per Justin's question about a formula for adding a breaker bar? Yeah, I get it I think. The force applied to the fastener will be the same no matter how much you spread out the work load. Kind of like lifting a car. The car's weight will remain the same no matter how long a lever one uses. Pretty cool.

 

So then why do my instructions insist I grab the handle in exactly the right spot? Just to maximize my leverage maybe?

 

Mac my question was a extension on the socket 12" 6" 3"
In school they swore it changed torque readings but from my google friend it changes nothing but I am not positive I believe that

Also here is a pic of mine
5B668FF1-2C70-43F8-8B6E-3CA4FB3CDBE2.jpg

Middle of my grip is 12"

 

Here is a page with different formulas. It states that a straight socket extension requires no change. Crowfoots, other odd sockets do. In my early days I was told straight extensions made a few lbs difference, but that doesn't appear to be the case.https://www.motorcraftservice.com/re...la_main_en.asp

 

I read that article. Great read

 

That's a pretty cool sight. Thanks for the link, '61.
I was taught the same thing, an extension changes the torque values.

 

Extensions absolutely do not change the torque, so long as they are concentric, although there are extension torque multipliers with planetary gears that do.

Anything that changes the length of the lever that's working on the socket (that is, anything that moves the axis of rotation) will change the torque value.
Crow's foot sockets have the axis of rotation about half an inch away from the attachment point of the ratchet, so that will change the torque.
Extensions are on the same axis, so they won't.

As for where to grip a torque wrench, if it's one of the "click" ones, you need to grab it roughly at the handle so that the clicker operates properly - it is designed to click when a certain linear force is applied to it (which corresponds to the torque at the axis), but if you grab it at or very close to the little pivot that clicks, you may not have enough force on the end of the wrench to trigger it.

In the old days, the torsion bar type wrenches needed to be grabbed at the right point to ensure the proper deflection of the wrench, which corresponds to proper torque indication on the scale.

- Eric

 

I have one of those "old days" torque wrenches. The main beam of the wrench runs through a hollow oversized handle that is connected to the beam with a pivot pin. This ensures the force is applied at the correct location.

 

It doesn't matter where you grab it as long as you're on the handle on this particular wrench. Actually if you COULD grab it 6" from the socket it would still give you the correct torque value (assuming it was calibrated correctly and you weren't bending the handle) as would any torque wrench. As stated previously "torque" is simply an (force x distance) ie. 60lb x 1 ft = 60 ft*lbs is the same as 120 lb x 6 in = 60 ft*lbs. If you really want to calibrate a torque wrench there's a machine called a Skidmore that's used. I used to build a lot of bridges (I wreck them now...lol), what torque ultimately wants to achieve is to elongate the bolt a set amount which in turn causes a consistent tensile gripping force.

 

Not with the old-style type. The reading of the wrench is based on the entire wrench bending as you pull it, while the pointer remains straight. If you pulled it anywhere other than the handle, you'd have less of the shaft bend than you are supposed to have, and the scale would read low.
That's why the handle is attached at a single pivot point.

- Eric

 

Yes and no
Within a few percent, your grip on the tool does not matter.

But, it does make a detectable difference.
I poo poo'd this idea until I was working in the tools repair dept at the Delta auto assembly plant, and part of that job was to verify calibration of the various torqueing tools. I tested my home clicker tool and it does matter where you put your hand on the tool. You would THINK that the tool would click at the same TORQUE regardless, but that is NOT SO.

Again it was not off by like 20% but it was detectable and repeatable. I vaguely recall around 5% different if one's hand is placed off the handle and closer to the socket.

 

Exactly.

Because when you are pulling on the wrench, you are pulling with a range of forces spread over a wide area.
You exert the most force with your index and middle fingers, the least with your pinky, but that force is spread over about 4".
So, as you think about it, a decent portion of that force is directed at the handle, quite close to the socket end, and, importantly, close to the pivot on the handle that clicks.
Obviously, if you are pulling right on top of the pivot, the handle will not deflect the spring, and the pivot won't click.
Less obviously, if you are pulling very close to the pivot, and are pulling in a straight line (not pulling the handle around the pivot, as though the pivot were the fastener's axis), the force you are exerting will not be efficiently activating the clicker, so the clicker will not click until the torque on the fastener is higher than the wrench is set for.

I would be curious as to the results of this experiment, if someone out there is equipped to perform it:
• Test a clicker torque wrench under proper operation to establish a baseline, then
• Test it again while gripping it short, once with your grip oriented with the pinky closest in, and again with your index closest in.
• My bet is that it will behave close to normally with pinky closest to socket, and least normally with index closest to socket.

- Eric

 

Well that sounds like a left-handed grip.

 

Ya gotta change it up now and then.