Re: Electric impact wrench info ?

[Kevin Ford <chery_ford@bc.sympatico.ca>]

Robert Myers wrote:

> 
> Isn't a lower torque an advantage sometimes?  Like when the yahoo uses an
> impact wrench to put your wheels on?  Most electric impact wrenches that
> I've used/seen reach about 75-80 ft-pounds which is about right for your
> lug bolts (81 ft-pounds).  An air operated wrench can twist those puppies
> right off if the yahoo has a mind to do it (or, as I suspect, is totally
> mindless).
> 

Impact wrenches are designed to remove stubborn fasteners quickly and 
easily.  For assembly, a more suitable tool is an air powered rachet 
(example typical 3/8" rachets have a torque of 50 ft-lbs), but for 
final torque, an air powered rachet operates like a convetional one, 
allowing the user to "feel" the torque applied.

For critical bolts, one must use a suitable torque wrench (that is 
sized for the torque rating, not at either end of it's scale) for the 
final tightening.  That means for audi wrenching, I have a 1/4", 3/8", 
1/2", and 3/4" (max 600 ft-lbs) torque wrenches.  (the 3/4" drive is a 
must for the crank bolt and the axle shaft nuts).

Good tire shops use a torque limiting device (they come in different 
torque settings) that look like a socket extention for their impact 
wrenche.  These are made of a spring metal, and cause the impact to 
jump out away from the fastener when the torque is reached, and not 
apply further turning force.  Good shops will also only torque alloy 
or performance rims with a torque wrench. 

If you use the proper tool for the job, the job has a much better 
chance of being done correctly (IMHO).  :)

Kevin Ford