At 11:30 AM 10/5/2002, Marla Stelk wrote:
>So just how important is it really to use a torque wrench?

Personally I think it's pretty important, especially working in aluminum
and particularly if you haven't developed a good feel for what is a
reasonable torque to use.  For myself I started using a torque wrench when
I got tired of putting in Helicoils because I'd pulled the threads out of a
hole by overtightening.

For some applications -- tightening the bolts holding on the alternator
bracket for example, and the alternator to the bracket (and heads and many
other mechanical assemblies) -- it is crucial to use a torque wrench
because while overtightening will pull out the threads or break the bolt,
*under* tightening will lead to later breakage of the bolt from
fatigue.  This is less of a factor when the bolt is greatly oversized for
the job -- for items like the thermostat cover, the bolt size (6 mm) is
probably chosen for standardization and ease of use rather than for the
exact strength needed for the job.  4 mm bolts would probably have plenty
of strength, but be much more finicky to install, more problem with
corrosion and one more item to keep on the shelf.

And then there are places where that torque wrench simply isn't going to
fit, even though it's necessary.  Best you can do is give it your careful
best shot with your calibrated arm, taking into consideration the length of
the wrench you're using.  Fifteen lb-ft is fifteen pounds at one foot
distance, or thirty pounds at six inches, etc.

While you're at it -- my own tendency is to buy a torque wrench that will
handle the heaviest job I will do.  Unfortunately most of the bolts around
the engine are torqued so lightly that it's impossible to read the torque
correctly on the big wrench -- so figure on at least two to cover the range
of work.  Three or even four if you're doing really heavy work.  Get the
small one now, and a bigger one later if/when you need it.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"