REALLY Basic Torque Question

[mwb]

Yes, you'll lose a bit of the torque value with an extention (or a crowsfoot,for that matter).
Do some research and you'll find a formula to factor in the extention.

However, I just add couple ft-lb's (or Nm's, if you into metric). One or two extra should do the job.

Just remember that torquing is not only to ensure the correct tightening of a fastener, it's to prevent overtightening, so don't go overboard on that torque value.

Careful with this! An extension will not reduce your applied torque. A crowsfoot will amplify (increase) torque at the nut unless you put it on backwards (open end facing the wrench handle.

The OP was not asking about a crowsfoot I only added that to make sure it was not confused with a 'normal' straight extension. The link I posted gives you the formula for correcting for crowsfoot; there is no change when using a normal straight extension.

If you apply a torque to one end of a pipe (think drive shaft) the torque on the other end has to be the same (but in the opposite direction). It would not matter if your extension was 0.5 inches or 50 inches long. The fact that an extension may twist under load does not change the torque that is transmitted.

 

[RoyJackson]

Careful with this! An extension will not reduce your applied torque. A crowsfoot will amplify (increase) torque at the nut unless you put it on backwards (open end facing the wrench handle.

The OP was not asking about a crowsfoot I only added that to make sure it was not confused with a 'normal' straight extension. The link I posted gives you the formula for correcting for crowsfoot; there is no change when using a normal straight extension.

If you apply a torque to one end of a pipe (think drive shaft) the torque on the other end has to be the same (but in the opposite direction). It would not matter if your extension was 0.5 inches or 50 inches long. The fact that an extension may twist under load does not change the torque that is transmitted.

Problem with your comment is, although torque is transmitted, the typical micrometer setting ("Click" type) torque wrench will trigger prior to the transmission of torque through an extension. This is negligible, but in aerospace, we did have to factor for it.
I use a 1/2" drive micrometer setting torque wrench and I need a 6" 1/2" drive extension to torque my rear wheel bolts. That extension is pretty darn stiff (resistant to twist). As written earlier, I "guesstimate" about 2 ft-lbs of added torque to accomodate it (which is probably within the tolerance of the torque wrench anyway).
So, the illustration of a drive shaft isn't quite accurate (for a comparison to a torque wrench) because it doesn't account for the triggering of the wrench.

Now, we've added some real complexity to a "REALLY basic torque" question, haven't we?

 

[timswi]

Wow!!! Setting 2 on my impact seems to have the right torque for all wheels

I know you should torque them, but to be honest, I never have. I run them down on the second setting and double check them with a 4 way. Never cracked or warped a wheel (steel or aluminum) in my life.

 

[gpflepsen]

Problem with your comment is, although torque is transmitted, the typical micrometer setting ("Click" type) torque wrench will trigger prior to the transmission of torque through an extension. This is negligible, but in aerospace, we did have to factor for it.
I use a 1/2" drive micrometer setting torque wrench and I need a 6" 1/2" drive extension to torque my rear wheel bolts. That extension is pretty darn stiff (resistant to twist). As written earlier, I "guesstimate" about 2 ft-lbs of added torque to accomodate it (which is probably within the tolerance of the torque wrench anyway).
So, the illustration of a drive shaft isn't quite accurate (for a comparison to a torque wrench) because it doesn't account for the triggering of the wrench.

Now, we've added some real complexity to a "REALLY basic torque" question, haven't we?

With all due respect, I don't see this as being valid. Any torquing operation should be as "static" as you can make it to ensure good results. Every system of forces is going to be conservative, that is force in = force out, or in this case, torque in = torque out. A flexing drive extension is no different than pushing a spring to push a load. Force applied = force transmitted. Always

I'm all for learning something new, so if you can tell the whys of your position I'd appreciate it.

 

[banjodunn]

G'day i will throw my 2 cents in now, I have got three ext bars that i use in conjunction with a "click" type tension wrench and use these for engine building i have my wrench calibrated every twelve months, and i also send my bars down to get checked, 2"ext looses 1/2 ft/lb, 6" looses 1.2ft/lb and 12" looses 2.3 ft/lb. So i guess that they are prob accurate enough to use an ext but at least i can allow for it, as far as wheels go though i have never tensioned one in my 20+ years in the trade and never had a prob.


Jon

 

[SPYDERLK]

Problem with your comment is, although torque is transmitted, the typical micrometer setting ("Click" type) torque wrench will trigger prior to the transmission of torque through an extension. This is negligible, but in aerospace, we did have to factor for it.
I use a 1/2" drive micrometer setting torque wrench and I need a 6" 1/2" drive extension to torque my rear wheel bolts. That extension is pretty darn stiff (resistant to twist). As written earlier, I "guesstimate" about 2 ft-lbs of added torque to accomodate it (which is probably within the tolerance of the torque wrench anyway).
So, the illustration of a drive shaft isn't quite accurate (for a comparison to a torque wrench) because it doesn't account for the triggering of the wrench.

Now, we've added some real complexity to a "REALLY basic torque" question, haven't we?

Yeah! ... Incorrect stuff. Youre putting people who dont know any better into jeopardy. Get physic.
larry

 

[mjncad]

I have this little chart I got at McMaster-Carr and it's in the same drawer as my torque wrench.

Use this handy guide to reference torque requirements for inch nuts in 1/4" to 4" sizes and metric nuts in M4 to M100 sizes. The guide has 56 pages and measures 3 1/2" Wd. x 5 3/4" Ht.

Each90662A050$6.70

 

[c23380]

use to build engine for piston aircraft. Standard practice is that extentions do not change the torque much, IE not enough to worry about considering the +or- tolerances given in the manuals. this being said there is a shortcut when using crows feet or any other adapter the is not in line with the wrench. If you allign the adapter 90 degrees from the torque wrench direction of force then the setting on the scale will still fall well within the range of + or -. cylinders on Lycoming and Continental engines were all done this way for 30 to 40 years at our shop. Just passing this as it was passed to me by our Cheif engine builder.

 

[Transit]

use to build engine for piston aircraft. Standard practice is that extentions do not change the torque much, IE not enough to worry about considering the +or- tolerances given in the manuals. this being said there is a shortcut when using crows feet or any other adapter the is not in line with the wrench. If you allign the adapter 90 degrees from the torque wrench direction of force then the setting on the scale will still fall well within the range of + or -. cylinders on Lycoming and Continental engines were all done this way for 30 to 40 years at our shop. Just passing this as it was passed to me by our Cheif engine builder.

X2:thumbsup:

 

[RoyJackson]

use to build engine for piston aircraft. Standard practice is that extentions do not change the torque much, IE not enough to worry about considering the +or- tolerances given in the manuals. this being said there is a shortcut when using crows feet or any other adapter the is not in line with the wrench. If you allign the adapter 90 degrees from the torque wrench direction of force then the setting on the scale will still fall well within the range of + or -. cylinders on Lycoming and Continental engines were all done this way for 30 to 40 years at our shop. Just passing this as it was passed to me by our Cheif engine builder.

Yeah, pretty much negligible for short (6"), but we had to go by the manuals, so we used the calculations for correction. Of course, there was more then one occasion we did have to use longer (12+") extentions which, according to the Navy and aircraft manufacturers, did have an effect.