Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old February 24th 08, 04:46 PM posted to rec.crafts.metalworking
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Default Impact wrench torque

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?


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Old February 24th 08, 04:58 PM posted to rec.crafts.metalworking
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Default Impact wrench torque

We use an IR 2135 to remove the center lug nut on a Porsche. These get
torqued to 340 foot pounds and left for a while, I figure breakaway
torque is around 500 foot pounds for removal. It won't do that on the
little compressor even if I charge it up to full 120 psi before pulling
the trigger. We usually do that job off of a N2 bottle regulated at 150
psi. Even then it takes a few moments to see it start to loosen and move.

I suspect you need larger hoses. I have a 3" cutoff tool that runs fine
in the shop, does not work at all well in the garage even though the
only difference is 50' of 1/2" ID copper pipe.

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

  #33   Report Post  
Old February 24th 08, 09:35 PM posted to rec.crafts.metalworking
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Default Impact wrench torque

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
  #34   Report Post  
Old February 24th 08, 11:04 PM posted to rec.crafts.metalworking
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Default Impact wrench torque

The GOOD shops have a torque stick instead of an extension bar, it
breaks loose at a specified (but somewhat inaccurate) measurement. Then
torque it up properly by hand with a calibrated torque wrench. The
mediocre shops use the torque stick alone. The bad shops have a bubble
gum brain impact wrench jockey pull the trigger until it is "good and tight"

I don't look down on a shop that uses an impact wrench for assembly as
long as they had start the bolts and had torque them afterward. It does
save a lot of time when doing a lot of similar bolts eg on the engine.

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

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Old February 25th 08, 12:16 AM posted to rec.crafts.metalworking
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Default Impact wrench torque

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



  #36   Report Post  
Old February 25th 08, 02:44 AM posted to rec.crafts.metalworking
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Default Impact wrench torque

On 2008-02-24, Joseph Gwinn wrote:
In article ,
clare at snyder.on.ca wrote:


[ ... ]

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.


Another factor is that the "wrench" which is struck benefits
from being light, as long as it is sufficiently rigid. IIRC, these were
advertised as being titanium, which is light but rigid. So make the
part which is struck to transmit torque to the actual wrench socket as
light as possible (titanium), and the hammer part as massive as possible
(tungsten?) for maximum transfer of energy to the nut.

Enjoy,
DoN.

--
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(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
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  #37   Report Post  
Old February 25th 08, 03:37 AM posted to rec.crafts.metalworking
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Default Impact wrench torque


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


  #38   Report Post  
Old February 25th 08, 05:36 AM posted to rec.crafts.metalworking
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Default Impact wrench torque


"RoyJ" wrote in message
...
We use an IR 2135 to remove the center lug nut on a Porsche. These get
torqued to 340 foot pounds and left for a while, I figure breakaway torque
is around 500 foot pounds for removal. It won't do that on the little
compressor even if I charge it up to full 120 psi before pulling the
trigger. We usually do that job off of a N2 bottle regulated at 150 psi.
Even then it takes a few moments to see it start to loosen and move.

I suspect you need larger hoses. I have a 3" cutoff tool that runs fine in
the shop, does not work at all well in the garage even though the only
difference is 50' of 1/2" ID copper pipe.


when I pull those wheel nuts off my 356, I use a 3/4 inch breaker bar and a
10 ft length of 1 inch pipe -the pipe will usually bend but it takes it off
nicely - I suspect more than 500 ft/lbs. I had one of those nuts unscrew
once, shearing the cotter and working it into the threads - this allowed the
wheel to separate from the car, taking the brake drum with it - I was going
down hill at the time and trailed an impressive rooster tail of sparks as
the shock tower ground down on the freeway - never did figure out why it was
able to shear the cotter pin, but I will always remember the feeling of
torque steer that preceeded the final separation by about 5 seconds. Oh,
and with the old 356, when the rear wheel goes you have no brakes (single
hydraulic system), no emergency brake (mechanical differential) and no way
to downshift to slow down (because of the differential) so you just get to
ride it out - it's quite a feeling.



--
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  #39   Report Post  
Old February 25th 08, 12:49 PM posted to rec.crafts.metalworking
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Default Impact wrench torque

Don Young wrote:


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


There are "calibrated" extensions, too, that limit the torque by being
of different diameters. Harbour freight probably sells them in the US,
but I know that Princess Auto in Canada does.

Cheers
Trevor Jones



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