air impact wrench for auto work

Reply

  #1  
Old 07-28-13, 02:36 PM
Member
Thread Starter
Join Date: Nov 2008
Location: West
Posts: 261
air impact wrench for auto work

I have a pancake style air compressor,2.6 at 90 psi 6 gallon Porter Cable.
I am not buying a new compressor. What impact wrench would be good for general auto work?? Should it be 3/8 or 1/2 ??? and do any have a built in torque rating at least roughly??
 
Sponsored Links
  #2  
Old 07-28-13, 02:59 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 46,906
Good questions. The pancake won't deliver much air though. It would probably be borderline on a 1/2" gun. A 3/8" may work ok.

Impact guns need high volumes of air......quickly. One or two pulls of the trigger could just about empty that tank. You may need to look into picking up a second tank that you can connect to the first one to store more air.
 
  #3  
Old 07-28-13, 05:08 PM
Join Date: Jan 2007
Location: North Central Indiana
Posts: 912
You better look at an electric. You dont have enough compressor for an air wrench.
 
  #4  
Old 07-28-13, 06:04 PM
Member
Join Date: Oct 2010
Location: USA
Posts: 563
Yeah, I'm not feeling it either. My 30 gallon compressor fails to keep up with balljoint removal and the like.
 
  #5  
Old 07-29-13, 05:30 AM
Member
Join Date: Jan 2012
Location: Canada
Posts: 2,542
As the others have mentioned, a compressor with a decent tank or a second tank will be needed.
The 90PSI probably won't be enough for most tasks. All the compressors I've had at home where ~125PSI cutoff which (can't remember the cut-in pressure).

As for the impact gun, I've had reasonable success with the cheap ones. Obviously the better guns will work much, much better, but will you get the use to justify the cost?
To improve the performance of your impact, keep the hose short (high quality) to reduce it from expanding under pressure. Also, I add a couple drops of oil in the inlet of my gun each time I take it off the shelf to use it. These two items will make a huge difference.
 
  #6  
Old 07-29-13, 06:23 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 910
Originally Posted by diy9999
I have a pancake style air compressor,2.6 at 90 psi 6 gallon Porter Cable.
I am not buying a new compressor.
There's a fair chance that any impact wrench will burn out that compressor.
Result being that you WILL be buying a new compressor.

Here's why. Your compressor is rated 2.6 cfm at 90psi.
Hold the trigger on an impact wrench and it pulls 25.4 cfm. And that's for the smallest impact wrench (e.g. my CH TL0502) which generates 60-250 ft-lbs.

The problem isn't CFM, it's duty cycle. Although PC is a good compressor, it's still oil less compressor so it's likely designed for 33% - 40% duty cycle. So for every 1 minute on - 2 to 2.5 minutes off.

Some quick gueses-
- eh, 1 minute for an impact wrench to drain a 6 gallon tank at 150psi?
  • Edit. 20 seconds to drain that air tank if it's at 150psi..

    6 gallons x .133681 CFM per gallon = .8 CFM tank volume.
    Atmospheric pressure is 14 psi, so at 150 psi that tank holds 10.7 times the volume.
    So .8 cfm tank filled to 10.7 capacity means 8.56 cubic feet of air stored in the tank.
    Wrench takes 24.5 CFM, so it should drain 8.56 CF in just about 1/3 of a minute.

- 5 minutes for it to refill to 150psi.
- 15 minutes for the compressor to rest.

End result, you can use the impact wrench for 20 seconds every 20 minutes.


As you add larger tanks, you are more likely to burn out the compressor filling up the tank.
It's likely designed to "run for 1, rest for 2".
If you add a 54 gallon tank, that's 10 times more air, so (guesstimating) 40 minutes of compressor run time to fill the tank. And running 40 minutes non-stop is going to kill your compressor in a short amount of time.
  • Edit larger tank may not help all that much.

    Say add a 54 gallons tank for 60 gallons total. That's 40 minutes on time, but filling is still limited by duty cycle, something like 5 minutes on, 15 minutes off.
    So 8 compressor cycles @ 20 minutes each, or 2 hours and 40 minutes for a 60 gallon tank.

    And that will give you about three and a half minutes of impact wrench time.

Originally Posted by diy9999
What impact wrench would be good for general auto work??
Small impact wrenches usually generate 60-200 ft-lbs. Medium up to 500 -750 ft-lbs.

In your situation, I'd think the most productive purchase would be an air ratchet.
Invest in a good breaker bar to loosen bolts, then the 30-60 ft-lbs from an air ratchet should
be sufficient to remove or snug the bolts.
 

Last edited by Hal_S; 07-29-13 at 07:42 AM.
  #7  
Old 07-29-13, 11:14 AM
Group Moderator
Join Date: Oct 2004
Location: WI/MN
Posts: 18,774
I have an electric impact wrench someone gave me before I had a compressor and it does a pretty fair job. As stated, pneumatic impact wrenches take a lot of air.
 
  #8  
Old 07-29-13, 07:46 PM
Member
Thread Starter
Join Date: Nov 2008
Location: West
Posts: 261
btw do all air tools need lubricating oil put inside the air inlet???? what is the best type oil to use??
 
  #9  
Old 07-30-13, 04:28 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA
Posts: 44,364
Most do, I'm not familiar with the ones that don't. They sell 'tool oil' for pneumatic tools but I've often used 3in1 oil when tool oil wasn't handy.
 
  #10  
Old 07-30-13, 04:53 AM
Member
Join Date: Jan 2012
Location: Canada
Posts: 2,542
I can't remember what oil I use. Bought a half pint for pocket change and have been using it ever since.
I add a couple drops to any air tools that are not intended to blow air on the item (i.e paint gun, sand blaster, tire adapter).
I had considered a auto oiler, but didn't think the mess in the hose would be a good idea for me considering I switch tools frequently.

I would suggest a moisture remover however. The one I have was really cheap and does take some water out of the air hose. Really good if you need to use the compressor in cooler (or cold) weather as the compressor heating the cold air can generate a bit more water which is bad for tools.
 
  #11  
Old 07-30-13, 05:01 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA
Posts: 44,364
I've not used them but the self oiling systems are supposed to work good BUT it renders the hose useless for any painting [and I'm a painter ]

I'd second the advice for a good moisture separator. I probably don't need it too much here in N.E.Tn. but when I lived in fla it was an absolute necessity!! With the fla humidity I needed to drain both the water separator and the compressor tank on a daily basis and depending on use - more often.
 
  #12  
Old 07-30-13, 06:23 AM
Member
Join Date: Jan 2013
Location: U.S.A.
Posts: 1,534
Tool houses carry air tool oil, but a buddy of mine, who repaired air tools as part of his living, always recommended Marvel Mystery Oil. In my opinion, the proper way to oil an air tool is to drip it directly into the nipple on the tool; automatic mist oilers are not as effective, and, as mentioned, render the hose useless for painting or other applications where you do not want oil. And yes, moisture is an air tools worst enemy, so a moisture trap should be considered essential. If possible, route a hose from the air compressor to the trap, and then from the trap to the tool, because the cooler the air is when it reaches the trap, the more effective the trap will be. Back to the opening post though, in all seriousness, with the size air compressor that you currently have, you will be deeply disappointed with a pneumatic impact wrench. Pneumatic wrenches have an edge in some areas, but none that matter if you cannot sustain the pressure and volume to effectively run them.
 
  #13  
Old 07-30-13, 07:27 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 910
Originally Posted by diy99999
btw do all air tools need lubricating oil put inside the air inlet????
Basically anything with moving parts that spin, shear, saw, vibrate etc, you want to add a few drops of oil before you use. Some big air wrenches have an internal reservoir that must be filled before they'll work correctly.

To keep oil in the tools, you can get air mist oilers that are usually mounted near the tank (about the size of a can of tennis balls) or there are individual tool oilers (about the size of a golf ball).


Originally Posted by diy99999
what is the best type oil to use??
No real consensus. You'll find it's all over the place.
Some people swear by (but others warn against) air tool oil, sewing machine oil, brake fluid, transmission fluid, chain saw bar oil, synthetic motor oil...
 
  #14  
Old 07-30-13, 08:01 AM
Join Date: Jan 2007
Location: North Central Indiana
Posts: 912
I have seen Marvel Mystery oil used in air tools for over 50 years.
 
  #15  
Old 07-30-13, 08:17 AM
Member
Join Date: Jan 2012
Location: Canada
Posts: 2,542
I have seen Marvel Mystery oil used in air tools for over 50 years.
I've never really put much thought in the brand or type of oil I've used. Heck, couldn't even tell you what the bottle looks like other then it's a light tan color around the top from the oil. Been using the same stuff year round, in plus and minus 40'C weather.
 
  #16  
Old 07-30-13, 08:41 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 910
Heck, couldn't even tell you what the bottle looks like other then it's a light tan color around the top from the oil.
Basically, any oil as long as it doesn't say "ULIVO", or "extra virgin"
That is, unless you're working on a Fiat... or Citroen (grin)...

(Some imports use green mineral oil for brake fluid, it looks like olive oil)
 
  #17  
Old 08-16-13, 01:36 PM
Member
Join Date: Jun 2009
Location: California
Posts: 214
That compressor won't run an air powered impact wrench, I have them from 1/4 inch to 3/4 inch and that compressor wont supply enough pressure at volume, it was intended to run a nail gun and not a big one. My brother in law has one.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes