impact wrenches and air compressors

how do the spec-s of an air impact wrench relate to the air compressor? i need to loosen a crankshaft pulley bolt that is torqued at 134 ft- lb. on a 1998 honda civic LX. i have a sears craftsman 1.5hp 4- gallon 4.7SCFM@40psi--3.3SCFM@90psi air compressor. i don't yet have an air impact wrench. what should i look for in terms of psi when i go to buy one, such that i can use that air compressor to drive the impact wrench to loosen the bolt? tia.

Reply to
gp8q18
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Your compressor could probably run 1/2" impact for a few seconds. After that you can wait for the pressure to build but, if the bolt is not seized, it should loosen in that time at full zap. If not, you will have to wait for pressure and try again. It should break loose fairly quickly assuming your impact is good for 200 ft/lb or more at 90 psi. Keep in mind the pressure at the impact will be considerably less than the pressure indicated at the compressor. You will probably need over 100 psi at the compressor to get 90 at the gun.

BTW, inexpensive impacts tend to use quite a bit more air than a top line gun at the same pressure and work load. Most of the less expwensive ones will use even more than their specs indicate.

Lugnut

Reply to
lugnut

I have a 5 gallon tank and 3 hp motor and can get about 5 seconds of good impacting with a 1/2" drive Campbell Hausfeld impact gun.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

I removed the crankshaft pulley bolt on my Mom's Civic. I tried three different 1/2" drive impact wrenches (one of them was a professional quality Ingersoll-Rand impact wrench borrowed from my ex-auto-mechanic neighbor) and none of them budged it after many minutes of trying. A 3/4" drive impact wrench from the rental store got it loose in a couple of seconds.

As the other poster said, cheap impact wrenches will suck up a lot of air, they're OK for most home jobs like undoing wheel lug nuts but for stuff that's really stuck you will like having a higher quality more expensive tool. And for really stuck stuff nothing will beat a FOAD 3/4" impact.

Reply to
Mark Olson

Crankshaft pulley bolts can be difficult to loosen sometimes.

90 psi may not do it. 110 psi would be much better. For a impact, just get a good brand name and it should be ok.
Reply to
Paul

They stretch the truth a bit I think.. those bolts are in there with a lot more than an 134fl-lbs of torque. You are going to need a 3/4 drive to get it off most likely.

You may be able to find a local shop that will break it loose for you and snug it back up if you slip them a $20. That's usually what I end up doing as they have the high powered stuff and my dinky home owner stuff just can't break them loose.

Steve B.

Reply to
Steve B.

I have loosened up and removed one or two crankshaft pulleys before with a 3/4 '' breaker bar and a big hammer or a 3/4 '' breaker bar and a cheater pipe.No impact wrenches needed.That was on vehicles with manual shift transmissions. Cheater pipes Rule! cuhulin

Reply to
cuhulin

Steve B. wrote in news:spfae41o4bmqho02u9lg6hvhjjul7vfprj@

4ax.com:

No they are not.

No. A 1/2" drive DeWalt DW-293 325 ft/lb electric impact wrench takes it off easily.

Reply to
Tegger

Sure seems like they are. I've tightened back to spec and it's no where near what it took to get the damn thing loose.

I think I'll save the $178 and just pay the guy $20 to bust it loose for me. I never met an electric impact wrench I was impressed with.

Reply to
Steve B.

Pressure matters less than volume. Most impact wrenches (most air tools PERIOD) are designed to work fine as long as you can give them 80 PSI.

Volume is another story- your compressor needs to be able to keep the tank pressurized as you use the tool. Impact wrenches aren't very demanding because you use them in short bursts, and even a very small compressor can re-fill the tank between bursts. Just don't try to make like a NACAR tire changer and whip 10 lugs on and off in less than 13 seconds...

The most demanding air tool in my kit is the smallest one- the cut-off wheel. Since it spins at high speed and is constant use, it keeps my

5-horse compressor running about 80% of the time. On the other hand, I can change 2 tires with the impact wrench just with a portable 11-gallon air tank filled to 120PSI and no compressor at all.
Reply to
Steve

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