Torque Values - Why the range?

[Concho Billy]

Howdy Everyone,

In the service manual, when giving a torque value they always give a range, i.e., 14-29nm.

I'm used to seeing one number. I tried to get an answer but no one I have talked has something concrete.

I talked to a HD wrench the other day and he says he's is not sure and he takes the lower number.

Is it a temp thing? Cold/Hot range?

Any help would be appreciated.

Regards,


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[FatBobRob]

i usually split it down the middle.

[Gulfstream]

I work in the aircraft maintenance industry and this is a standard practice. On fasteners that require a cotter pin the range is there to provide lining up of nut castellations and cotter pin holes. The range is the "acceptable range" for the given fastener and its intended use. I sometimes like to make all the flats line up in a certain way (ie. 12 and 6 o'clock flats horizontal) so I can look at then and see if they have moved...guess that could put me in the anal category but it gives me a quick visual method of identifying fasteners that have broke torque. Generally I recommend that new bolts are torqued to their higher range because they will stretch and in-service bolts to the lower spec since they have already stretched...but you can't go wrong with the mid value.

[Concho Billy]

Originally Posted by FatBobRob

i usually split it down the middle.

Thanks Rob. That's what I have been doing, just wasn't sure if that was correct.


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[Concho Billy]

Originally Posted by Gulfstream

I recommend that new bolts are torqued to their higher range because they will stretch and in-service bolts to the lower spec since they have already stretched...but you can't go wrong with the mid value.

John,

Excellent answer! Thank You for taking the time.

Regards,



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[fauskar]

If you read the service manual, it's stated: the lower number is used to re-check tightness. The upper number is used during assembly.

Set the T-wrench to the lower value and attempt to re-torque the item. If the wrench breaks/tics at the lower value, the item is still within specification. That's the pupose of the two values.

[84FXRP]

Originally Posted by fauskar

If you read the service manual, it's stated: the lower number is used to re-check tightness. The upper number is used during assembly.

Set the T-wrench to the lower value and attempt to re-torque the item. If the wrench breaks/tics at the lower value, the item is still within specification. That's the pupose of the two values.

FAUSKAR - Read the service manual! What a unique concept!

[Ed Y]

Originally Posted by 84FXRP

FAUSKAR - Read the service manual! What a unique concept!

Yep, sure is. Brings to mind a poplular term used often during my naval service,
RTFM or "read the fu....... manual".

[Concho Billy]

Originally Posted by fauskar

If you read the service manual...

Thank You fauskar for the explaination.

I take the SM into the bathroom with me twice a day and thought I read the SM inside-and-out to find that but quess I missed it.


Regards


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[DR_DEUCE]

a service manual..................gee, that must be whats under my PLIERS!!

[fauskar]

Don't feel bad you didn't catch it, it's in the very forward sections of the manual. The sections we skip to get to the meat of the manual. At least that's were I think I read it.

[helotaxi]

Originally Posted by Gulfstream

I work in the aircraft maintenance industry...I sometimes like to make all the flats line up in a certain way (ie. 12 and 6 o'clock flats horizontal) so I can look at then and see if they have moved...guess that could put me in the anal category but it gives me a quick visual method of identifying fasteners that have broke torque.

As a pilot, I can appreciate anal retentiveness in a mechanic