my take on torque

[auditude at cox.net]

Hey list,

I have just a couple excerpts to comment on, which are below.

SJ <syljay at optonline.net> wrote:
> 
> Changing the extender length at the socket, and/or changing the torque
> wrench length(not by adding a pipe, but using a longer wrench) affects the
> resultant torque at the bolt.

This is the statement I have a problem with, the part about a longer torque wrench changing the bolt torque.  Why?  You still stop applying force when the torque wrench tells you that the bolt has achieved the required torque (by either clicking or pointing to the right spot on the scale).

Are you saying that the force necessary at the handle is decreased for a given torque value at the bolt?  I would agree with that, but not with what you wrote.

A one foot torque wrench applying 100ftlbs of torque on a bolt puts the same torque on the bolt as a two foot torque wrench applying 100ftlbs of torque on the bolt.  It would take less force on the end of the torque wrench, because it is a longer lever, but the torque at the lug and bolt isn't affected.  If you can explain why it would be different, at the lug and bolt, then I would accept it.

> > Hmmm.  So if the "click" point of the torque wrench is not at the same
> point as the center of the bolt being tightened (it's in between that point
> and the handle), then at that point it is not measuring the "twist" that's
> occuring at the bolt, but the force applied in a single direction at the
> click point.
> **** "Click point" is irrelevant. Its just another excursion into muddy
> waters. Replace the click wrench with a beam balance wrench. Now you have no
> "click point" to worry about.

Ok, then let's forget about click point.  Let's change it to a different point, the point on the wrench where the torque is being measured at, aka the bolt.  My suggestion is that "only" extensions that move the bolt away from the lug of the torque wrench will change the actual value relative to the measured value.  Extensions made opposite the lug do not change the lug to bolt distance so don't change the measured from actual torque.

Cheers,

Ken