In article ,
clare at snyder.on.ca wrote:

On Sat, 23 Feb 2008 11:46:26 -0500, Joseph Gwinn
wrote:

In article
,
mark wrote:

I bought what is apparently the most powerful 1/2" drive impact wrench
available IR 2135 with 1000 ftlb of torque and am still finding it
weak.

What torque is your arm rated for? It seems unlikely that any human can
put a 1000# push on a handheld tool that might be 12" in diameter at
most.

Joe Gwinn

The mass of the wrench absorbs the "instantanious torque" or "impact".
Mean torque, or average torque, may be as little as 100-150 ft lbs and
still have a 1000 ft lb rating - without stretching things at all (or
very little)

OK, makes sense. Same theory as the traditional striking wrenches. But
the wrench must be pretty heavy to achieve such a number.

But I still suspect that the 1000# may be a better measure of their
marketing versus their impact wrenches. The instantaneous peak torque
one will achieve will depend on how stiff the nut assembly in question
is. I assume that this is measured while trying to twist a piece of hex
stock welded to an anvil-sized hunk of iron. A better measure might be
the rotational inertia of the hammer assembly plus the rotational speed
at impact, combined into the angular momentum at impact. Such a measure
would be more useful in deciding the relative strength of an impact
wrench.

Hmm. The above metric won't work. A very light hammer moving fast will
have a large angular momentum, but will be ineffectual in breaking stuck
fasteners loose - the hammer will just bounce. The surface may become
battered, but the nut won't turn. The hammer must be heavy, just as
when using a handheld hammer to force something apart by banging on it.

Or a handheld hammer-activated impact wrench. I always used at least a
two-pound hammer, sometimes five pound. The objective was to use a
sufficiently large hammer that one blow would reliably do the job. This
is how I got aluminum screws out of aluminum castings without damage, to
get the alternator cover off of 1970s Japanese bikes. You got one
chance before the #2 phillips screw was mangled beyond hope. They came
loose with a very loud Crack!

This requires some thought. There must be a metric that captures the
effect of hammer weight on effectiveness.

Joe Gwinn


The other day it would not remove the bolts that hold on my
front brake caliper bracket and sometimes it wll not remove lugnuts. I
am using it at 125psi with 50' of 3/8" hose and 1/4" M (milton) quick
connects). Would going to 3/8" qc fittings help at all? I notived a
local tire shop has the air pressure at 150 psi. Is this what is
needed? How come air tools say never to go above 90 psi?