clare at snyder.on.ca wrote in message
...
On Sun, 24 Feb 2008 21:35:30 +0000, Mark Rand
wrote:

On Sat, 23 Feb 2008 21:00:11 -0500, clare at snyder.on.ca wrote:

I never reduced the pressure on my impacts from the 150 shop line
pressure. Mine DID have a "power" adjustment that allowed me to dial
the wrench back for assembling, and dial it up for dissassembling.


/RHETORICAL
How do you get accurate torque when assembling with an impact wrench?

The wheel nuts on my car require 81lb-ft of torque (put the wheels on
today
after a brake job) they assemble and disassemble easily by hand. A shop
uses
an impact wrench on them and they don't until they've undone them and
re-done
them with a torque wrench! The crankshaft pulley needs 200lb-ft. Also a
manual
job, just use a longer handle.


I can understand the use of an impact wrench for undoing truck wheel nuts,
but
with anything less than 400 lb-ft I would question the use of power tools
for
assembly. Much above that and I would be using a crane and balance. For
large
bolts, I would be expecting to use either hydraulic bolts or heated bolts
and
a micrometer, per the drawings.
/RHETORICAL


Am I being excessively picky?


Mark Rand
RTFM
Assembly with an impact is strictly a "speed" thing.
With the proper "torque stick" and the proper technique, it is
possible to "torque" a wheel nut accurately with an impact
wrench(within less than 10%)
I have, for decades, made a practice of putting the wheels on with the
impact wrench, then going around and checking the torque on ALL the
studs with the torque wrench before letting the car out of the shop.

I generally check my own vehicles again after 50-100 miles of driving.

On truck wheel nuts a "geared" torque wrench is often used (planetary
drive multiplier)

--
Posted via a free Usenet account from http://www.teranews.com

I have seen shops use a torque wrench after an impact wrench but they only
checked that the torque wrench would click in the tightening direction. In
other words, they did not check that the lugs might already be too tight
after using the impact wrench.

Effective use of a torque wrench in loosening tight fittings requires that
the whole assembly be very rigid. It takes only a short extension or a thin
socket to reduce the power significantly.

Don Young