torque wrench question

[chickey191]

does adding an extension to a torque wrench appreciably change the torque application to whatever you are torqueing? Just wondering.

 

[Ignacio]

Gawd I hope you're not trolling here. If so, I'm a fish on......

Otherwise, here's my answer without the benefit of somebody like Tom Austin responding.

No. It wouldn't change the torque being imparted on the joint any as long as your extension doesn't interfere with the head area of the wrench any. The amount of effort you exert with your arm would feel less and you'd have to move it farther, but the torque part of the wrench is still going to click at the same torque setting.

My concern would be that if you're needing to put on an extension......are you at the limit of the upper range of the wrench?

Do I win some prize now?

 

[mdisher]

No Prize for you, you are lose!

I think he's talking about the other kind of extension

From the head to the socket no?

Unless you get ya one of them fancy swivel jobbies to get to hard to reach places, it should not.

 

[Ignacio]

....extension.....ahhhh. :blink: I clearly was thinking "cheater bar".

Then my answer is different. It could make a difference unless you're able to twist it at a very clean right angle and somehow support the extension. You could overtorque it.

 

[pawtracks]

Basically as long as your extension does NOT increase the length of your torque wrench your indicated torque will still equal your actual torque (what you are really after - why you are using one in the first place)

If the extension is 90 degrees from the torque wrench you are fine.

If it makes your lever longer then your actual torque no longer equals your indicated torque.

A few equations:

here or here

 

[Rickster]

some confusion here on the question. I'll give it a shot.

If you're talking about a socket extension like:

then -- no, that won't affect torque.

If you're talking about a cheater bar over the wrench handle -- that would depend on the type of torque wrench, a 'clicker' break-over type will be ok if you put a pipe over the handle, and don't interfere with any moving parts.

If it's a beam type -- you can't interfere with the beam deflection:

If you're talking about an offset extension (like a crow's foot or spanner) -- yes it matters.

Like:

or

 

[Luke]

Use a very short extension. A long one will have some slight twist/flex which will reduce the actual torque in the higher torque ranges.

 

[chickey191]

....extension.....ahhhh. :blink: I clearly was thinking "cheater bar".
Then my answer is different. It could make a difference unless you're able to twist it at a very clean right angle and somehow support the extension. You could overtorque it.

Nope = wasn't trolling, but I should have been more clear - I meant Socket extension - not a cheater bar. I would think that there would be some torsional loss of torque when using an extension, but wasn't sure. intuitively - I would think that a short extension would present no problem at all. the longer the more torsion deflection there would be.

I guess then the question would be - assuming that the above is true....

at what length would it take to make a discernable difference in torque settings.

"discernable" as defined by "makes a difference of more that 1 ft. lb. of torque

that should keep someone busy for awhile

 

[Rickster]

Actually it's a fairly easy question to answer, but you may not like the answer.

The easiest way is to just put your assembly on a torque analyzer and see what it does. most any NIST certified calibration or metrology is certain to have one. you will be able to adjust the wrench to get the specified torque.

Note: unless the clamping force has 30% margin, then using the torque of the fasteners is not an acceptable practice.

Note: If you are concerned about 1 ft-lb, note that most commercial torque wrenches are only certified to hold 5% accuracy and precision, so if you have a standard 3/8" clicker type torque wrench 100 ft-lb max, then the wrench itself will be off much more than the torsion in 3/8" X 10" extension.

The torsional properties of your extension will be predicated on the steel and hardening process used, again -- gotta measure it on an analyzer. LINK to get one (ebay) Ebay link

EDIT: Here's a link on the strength of some metals -- Clicky

EDIT:and a link to some bending properties: Clicky