Torque wrench and an extension?

[Strouty]

I have to torque down some head bolts and even if I use a deep socket, the torque wrench will not reach. My question is........ can I use an extension, (4"), and if I can do I need to adjust my torque specs? They are torque to yield bolts, so I have to turn them a quarter turn tighter after they reach the specified torque. I know not to use the torque wrench for that.

 

[ghnl]

Yes and no. (If you mean a straight entension.)

Yes, you can use a straight extension and no, there is no need to adjust the torque value.

 

[Chuckw]

Adapters that by their nature change the effective length of the torque wrench (to increase applied torque or when using crows-foot/flare adapters) Conversion formula needed here (except when adapter is perpendicular (90 deg) to the axis of the torque wrench) When possible mount crowfoot or flare adapters at 90 deg. More on this below.

2. Extensions in the classic sense (extends in length on axis with the drive of the torque wrench; can be thought of as making the fastener taller. This extension will always "lose" torque (spring twist) but this is a non issue. No conversion formula needed.

The simple formula for length increase is directly in line with the axis of the handle; if there is any angle (like to get around an obstacle) it gets more complicated. If the angle is 90 deg no conversion is required - 30 pound/ft indicated would equal 30 pound/ft at the business end of the adapter no matter how long it is. Neat, huh?

chuck

 

[Mike83]

Oh no. Not this **** again...sigh.

 

[ghnl]

Oh no. Not this **** again...sigh.

If you don't like answering questions or the topic upsets you so much why do you reply at all? Why not just skip the thread?

 

[Mike662]

To the OP...the reason you'll probably see some reservations (like those expressed by Mike83) is that this topic has been discussed here before, and those discussions lead to a fair amount of disagreement. Also, the discussion of torque values can get pretty technical.

Let me see if I can accurately state the consensus of the previous discussions....

Adding an extension (in the traditional sense of the word...one of these...

http://buy1.snapon.com/catalog/item.asp?item_ID=1626&group_ID=238)

...there is no need to adjust your torque specs. There may be some minor effects due to the twisting of the extension, but the general consensus was that those effects (if they exist) are too small to matter in most applications. If you're working on a 747, that may not be the case, but again, the consensus was that for automotive work, there is no need to change the setting on the torque wrench.

Anything that changes the effective length of the torque wrench, however, (like a crowsfoot) does require an adjustment. You should be able to find the formula online, and it's probably posted somewhere here on GJ as well. FWIW, I know many torque wrenches come with documentation that includes the correct formula.

If I misstated anything, I'm sure our more senior members will chime in with corrections.

 

[Merkava_4]

Oh no. Not this **** again...sigh.

LOL!!

 

[AustinRoepke]

I have a crappy torque wrench, but a few statics classes under my belt.

Increase the rod behind whatever measures the torque, and you will have absolutely no affect on the value. That's the safe bet.

 

[Strouty]

I thank you guys for the answers, I tried to search, but I was on my phone and so much came up, just figured it would be easier to ask. My question was answered perfectly.

 

[rsanter]

an extension will adsorb some little amount of the torque you are applying to the fastener and will throw you reading off a little.
the rules I would follow are:
use the shortest extension you can
use the best quality extension you can that will have the least amount of flex or twist in it while using it

bob

 

[mrholeshot]

Because they are torque to yeild bolts your initial torque will prob be between 45-60lbs. If you go the other stated 90 degree turn it really won't make any differance as long as you are using a good extention that doesn't twist. When I have to use an extention I use the maximum torque called for. Just make sure the treads are cleaned and lubed (or sealer for the ones that hit water jackets. Thats a bigger factor than the differance a 4 inch extention poses

 

[caper]

Just make sure the treads are cleaned and lubed (or sealer for the ones that hit water jackets. Thats a bigger factor than the differance a 4 inch extention poses

Only lubed if your using a lubed torque spec.Lubed threads and a dry torque spec will result in an over torqued bolt.

 

[mrholeshot]

Only lubed if your using a lubed torque spec.Lubed threads and a dry torque spec will result in an over torqued bolt.

If using something like ARP lube will it really over toeque a bolt but on a torque to yeild bolt the initial 45-60 psi won't see much differance. If it was just a straight hard torque bolt it would make a differance as far as over torque. In his case with TTY consistant torque is the most important thing. I have to use a differant torqure value on hard torque bolts when I use ARP lube. A light oil or sealer won't change the torque value enough to worrry about.

 

[Moose-LandTran]

an extension will adsorb some little amount of the torque you are applying to the fastener and will throw you reading off a little.

If you're using a straight extension that isn't touching anything (ie frictional loss) then it won't alter the torque reading/output. There's nowhere for the torque to "go". In the case of an impact gun some torque will be "absorbed" by flex of the extension.

If you're using an angle gauge use it on the socket and the extension above it, you'll get a more accurate reading that way as it won't be affected by twist/flex of the extension.

 

[Chuckw]

No one mentioned lube,,,,,that changes everything...

 

[mrholeshot]

If you're using a straight extension that isn't touching anything (ie frictional loss) then it won't alter the torque reading/output. There's nowhere for the torque to "go". In the case of an impact gun some torque will be "absorbed" by flex of the extension.

If you're using an angle gauge use it on the socket and the extension above it, you'll get a more accurate reading that way as it won't be affected by twist/flex of the extension.

I was assuming he didn't have a torque angle meter in his situatin. lol

 

[Moose-LandTran]

No one mentioned lube,,,,,that changes everything...

You might want to read post #12.

 

[Moose-LandTran]

I was assuming he didn't have a torque angle meter in his situatin. lol

You can get them for $10. I wouldn't skip using one.

 

[caper]

A light oil or sealer won't change the torque value enough to worrry about.

I beg to differ with you and have had it proven to me in a course on bolts and torque wrench useage by a large bolt manufacturer/distributor.It was demonstrated through the use of a pressure transducer which measured pressure applied by a bolt at certain torque settings.A "dry" bolt was torqued and then another bolt was taken and just held in the instructors hand to allow his sweat to lubricate it and then torqued with the wrench at the same setting as the dry bolt.The transducer showed that the sweat lubed bolt was exerting about 15-20% more pressure than the dry bolt.This was with both bolts torqued to the same setting on the torque wrench.We were taught that any bolt that had been handled should be considered lubed and that unless we cleaned the bolt threads prior to install with brake kleen we should be torqueing using the lubricated specs.I had to sit through 8hrs of class on bolts a few months back.That was a looong day.

 

[Coach James]

No one mentioned lube,,,,,that changes everything...

That's what she said!











Coach

 

[Ironcrow]

Extensions in the classic sense (extends in length on axis with the drive of the torque wrench; can be thought of as making the fastener taller. This extension will always "lose" torque (spring twist) but this is a non issue. No conversion formula needed.

There may be some minor effects due to the twisting of the extension, but the general consensus was that those effects (if they exist) are too small to matter in most applications. If you're working on a 747, that may not be the case, but again, the consensus was that for automotive work, there is no need to change the setting on the torque wrench.

an extension will adsorb some little amount of the torque you are applying to the fastener and will throw you reading off a little.

And this is why the subject comes up again and again and creates some bickering. As it will until everyone gets it right. The effect of extensions on a torque wrench setting is always exactly and precisely ZERO. Car or 747. Always.

 

[foul_ball]

And this is why the subject comes up again and again and creates some bickering. As it will until everyone gets it right. The effect of extensions on a torque wrench setting is always exactly and precisely ZERO. Car or 747. Always.

For what it's worth, I do work on 747s and my employer agrees with you. My employer also says that for bolts less than 1" diameter, I can use (1) wobble extension or (1) ball/swivel adapter to apply torque so long as the deflection does not exceed 15 degrees. The universal "yoke-style" adapters are strictly prohibited.

 

[Moose-LandTran]

My employer also says that for bolts less than 1" diameter, I can use (1) wobble extension or (1) ball/swivel adapter to apply torque so long as the deflection does not exceed 15 degrees. The universal "yoke-style" adapters are strictly prohibited.

I was wondering about that yesterday. Does a yoke-type universal joint affect torque accuracy? If so, how?

 

[spongerich]

Torque wrenches are for sissies anyway. I always grab my biggest ratchet, slip on a 2' piece of iron pipe and jump on it a few times... that way you can always be sure you're making things tight enough.

 

[foul_ball]

I was wondering about that yesterday. Does a yoke-type universal joint affect torque accuracy? If so, how?

I'd love to get a look at the lab data myself, but I don't know who even has access. I just know the wobble plus style extentions I use make my life a lot easier. Plus, they don't go flaccid like the universal type when you can only get one arm into a crevice to put a socket on something.