Calibrating torque wrenches, was dist. rattle

auditude at auditude at
Wed Jan 28 09:59:09 EST 2004

Bernie Benz <b.benz at> wrote:
> > From: auditude at
> > 
> > Bernie,
> > 
> > Well, maybe we're used to different terms.  To me, when something is
> > calibrated, it is reset
> > against the standard.  Something is changed to bring it within the tolerances.
> A calibration is the quantification of the error characteristic over a
> defined range, and does not imply a scale change to bring the indicated
> within a given percentage of the actual.
> > 
> > Like with some video cameras you do some kind of calibration setup against
> > something
> > white before you use it (don't know if that's current technology).  Or when I
> > look down at the
> > bathroom scale with nothing on it and it shows 4 pounds, when I reset it to
> > zero before using
> > it, to me that is calibrating the scale in a way.
> A zero adjustment is a trivial part of a calibration.  If the response error
> is linear relative to the indicated scale, i.e. reads 10% high for all
> readings over the range, one has a simple to apply calibration, or
> correction factor.  Such is not always the case, requiring a more complex
> correction formula or look up table.  The indicated reading is less than
> accurate until corrected per the current calibration table.  The scale
> numbers may be meaningless, 1 to 10, until the correction factor is applied,
> i.e. 10.5 ft lbs per division.

Okay, those are nice technical terms.  But I guess I didn't see where you answered my question.  What do you Do Yourself to fix a torque wrench that doesn't work, just replace it?  Do you apply a correction factor to all its measurements?

> >  This is different to me  than putting on a 5
> > pound weight to verify that it measures 5 pounds, and therefore requiring no
> > adjustment at
> > all.  The words I use in that instance is a calibration check, altho' I'm not
> > asserting that it is
> > the correct or best term to use.
> > 
> > Altho' it's not necessarily a technical definition, we can look to trusty
> > to see if
> > it helps.
> > 
> >
> > 
> > cal·i·brate     P   Pronunciation Key  (kl-brt)
> > tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates
> > 1. To check, adjust, or determine by comparison with a standard (the
> > graduations of a
> > quantitative measuring instrument): calibrate a thermometer.
> > 2. To determine the caliber of (a tube).
> > 3. To make corrections in; adjust: calibrated the polling procedures to ensure
> > objectivity.
> > 
> > I'm using either the "adjust" portion of definition 1. or definition 3.  It
> > sounds like you are
> > referring to just the "checking/determination" portion of definition 1.
> > 
> > Or maybe you are using the same definition as I am, but you haven't yet
> > described what you
> > Do Yourself when the wrench doesn't repeat the correction measurement against
> > the
> > standard?  I guess with a pointer style you can maybe bend the pointer, but
> > with a click type
> > I wouldn't know what to do.
> > 
> > If the report that came back with my torque wrench showed that it was as
> > effective when I
> > got it back as it was when I dropped it off, then for sure I wouldn't think it
> > was worth the
> > money.  But since they changed something in it or about it to make it more
> > effective, and I
> > don't yet know how to Do That Myself, I figure it was worth it.
> If one does not know what he has paid for, it most probably was not worth
> the price.

Since my torque wrench now works better than it did when I sent it in, what does that last statement have to do with this thread?  

There is a such a thing as "core competency" you know, where you outsource things that can better be done efficiently and effectively by someone else.  Nowhere in this concept is there a requirement to fully understand the methods used.  The end result is what's relevant.

My not knowing how they made it better is only a problem when I try to DIY the calibration of my torque wrench.  I was waiting for you to explain how you Do That Yourself, and I guess I still am.  If it's not possible or practical, just say so.



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