Torque 3

[jhampton1970]

Is there a formula to estimate the added torque needed when using an extension or elongated socket?

I was given a general rule of +10% for every six inches of extension from a seasoned millwright. Nevertheless, I have looked in the 26th edition of the machinery handbook, and a few other places, with no luck.

It is understood of the many variables i.e. surface friction, lubricants, etc. My goal is something in general.



Regards,
Jason Hampton
-Freedom isn't free!

 

[ivymike]

What's the added torque intended to compensate for? Misalignment of the tool?

 

[CoryPad]

Are you referring to tightening of threaded fasteners?

There is no need to change the applied torque due to socket/extension length variation. However, long extensions can twist, so the rotation angle will be different.

Regards,

Cory

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[jhampton1970]

CoryPad,

Don't you feel it necessary to add torque to compensate for the possible loss of torque by the extension? The extension will flex and not yield the desired amount of torque due to the twisting effect.


Regards,
Jason Hampton
-Freedom isn't free!

 

[GregLocock]

Not in our universe.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ivymike]

The extension will flex and not yield the desired amount of torque due to the twisting effect.

well, maybe if it's rapidly accelerating...

 

[JStephen]

There are methods of estimating torque by the angle of the turn, maybe the millwright is thinking of something like that. And there would be a reduction in the maximum amount of torque that could be applied. But if you're using a torque wrench, the torque it shows should be what is applied to the fastener.

 

[electricpete]

If you put a crows foot on the end of the torque wrench, then you have to correct the torque reading on the wrench based on a ratio of distances. Once distance is the point of force application to the normal socket position, the other distance is the point of force application to the extended socket postiion.

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[electricpete]

Here is a link:

http://maintenanceforums.com/eve/ub...f=119103451&m=573108107&r=475108107#475108107

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[electricpete]

I'm not sure if that link is readable, it works find for me but I recall it may require cookies (have to go through a login process). If you guys can't read it let me know and I will cut/paste relevant portions.

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[CoryPad]

epete,

It is readable.

Regards,

Cory

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[Tmoose]

Several times in the last 40 years I have heard thoughtful, well-meaning folks mention the need to adjust torque when using an extension. I think part of the problem is the venerable Sturtevant/Richmond "Torque Manual" refers to, and even defines an "extension" as "a rigid bar...extending longitudinally forward from the axis of, and is attachable to, the drive square for the purpose of increasing the range of the Torque wrench...... "

That same concept and even nomenclature is used lots of places.

http://www.tpub.com/content/howitzers/TM-9-2350-304-34-1/img/TM-9-2350-304-34-1_239_1.jpg

Sadly we Tool users who frequent the Sears and Snapon catalogs know an "extension" as something quite different. More than once nothing less than trials with real tools and real fasteners would get everyone back on the same page.

 

[electricpete]

Tmoose - I don't understand you point.

Is it:

1 - you don't like the word extension to refer to something similar to what shown in your link? In that case what does extension mean to you?
2 - you disagree with applying a correction for the setup shown in your link?
or
3 - something else?

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[ivymike]

you DO apply a correction for the "extension" shown in the link.

you DO NOT apply a correction for the device commonly known as an "extension" (6in extension bar shown here

http://www.sears.com/sr/javasr/prod...&subcat=Socket+Accessories&BV_UseBVCookie=Yes

)

 

[ivymike]

the OP was referring to the latter version (Is there a formula to estimate the added torque needed when using an extension or elongated socket?)

 

[CESSNA1]

jhampton1970: The equation you are seeking is:

toque applied to the bolt = Reading on torque wrench * (1 + length of extension/length of torque wrench).

Thus; if a torques wrench reads 100 in-# what is the torque on a nut if there is a 6 inch extension on aan 18 inch torque wrench.

M = 100 * (1 + 6/18)
M = 100 * (1 + .333)
M = 133 in #

Regards
Dave

 

[ivymike]

oh yeah? Then what should he use for deep-well sockets?

 

[rb1957]

it looks like people are reading "extension" and understanding two different things ... either an extension in the torque moment arm (like cessna1 above) or an extension along the tightening axis (so that the body of the wench is further away from the nut/bolt) (like ivymike)

maybe the OP should clarify ?

 

[CESSNA1]

rb1957: You are correct. I was unclear in my response the extension I am talking about it the horizontal extension off the end of the torque wrecnh that increases the overall length or moment arm of the torque wrench. An extension alone the tightening axis need no correction.

Thanks
Dave

 

[Fabrico]

Jason, even if the extension is 20 feet long, it will have equal torque at both ends. Any difference between torque applied at the wrench head and that delivered to the fastener, can only come from misalignment.

Some confusion comes from impact tools, which of course, none of this applies to.