Air Compressor For Impact Wrench

11/23/2007

For my home use, I might occasionally need an impact wrench for things that you can't do without one. I'm thinking things like removing the bolt at the center of a harmonic balancer, etc. So what is the minimum compressor required to operate a good 1/2" impact wrench to remove a single bolt such as this? I'm not going to disassemble an engine with it or anything like that, just use it when I can't get the job done otherwise. The reason I ask is that Sears has some small compressors on sale for good prices. The reason I'm considering a small compressor is that I don't have room in my garage for a large compressor. Plus I think I could use a small compressor to run a nail gun for various carpentry jobs around the house that we have planned.

Sears sales for tomorrow:
2 gal. or 3 gal., 125psi, $79.99
5 gal. $139.99
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You want a compressor that puts out a minimum of 5.0 scfm at 90 psi, preferably more like 5.5 or 6 or so.
5.0 and a good impact wrench is good for about everything.

Don’t think it will properly do a harmonic balancer bolt, though. It would take a whole bunch of compressor and impact for that. Do the breaker-bar-and-bump-the-starter method.
Ron Porter
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When I did Seth's 98, I used an IR 231HA with my 25 gal Craftsman compressor (5.5 cfm @ 90) and ripped the harmonic balancer bolt off with ease. I have the pressure set to 145 psi.

Once upon a time (early 90's), this was THE 1/2 inch impact wrench to have if you turned wrenches for a living. They have way better stuff now, but the 213HA can be had at Lowe's for under $100.00 at times.

I agree, however, that it would take way more than a 2 or 5 gallon compressor. They're good for filling up tires, or running a nail gun. But for working on cars, you need more.
Dave Garber
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A quick survey on Sears... It takes a 1.5hp or above compressor to achieve 5scfm, and most 1/2" impact wrenches specify somewhere between 4 and 5 scfm. Compressors of this type start at $200. Like I said, Sears has a 3 gal., 1hp on sale for $80. At 2.4scfm it might run a 3/8" impact continuously. Equally important for me it is small so I could find a place for it in my crowded garage. I see a good assortment of compressors on Craig list, so I might wait for a cheap used compressor there.

By my calculations:
A 3 gallon tank is .4 cfm. If the compressor will run it to 125 psi, and you run the impact enough to run it down to 90 psi, you've taken roughly 2.3 atmospheres out of it, meaning roughly .9 cfm, meaning it should run an impact wrench for 10 seconds before the pressure drops below 90 psi. In my experience in the shop, most uses of the impact wrench require 2 seconds or so per fastener. A stubborn fastener might take more, using a puller on a stubborn harmonic balancer takes a lot more. So I'm guessing a 3 gal. tank would allow a person to attack a stubborn fastener, but not hit repeated fasteners, even if the stubborn fastener required you to stop and wait for the tank to pump back up for a second or third hit. This would be sufficient for my limited use at home.

bjshov98
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I like most of what Sears sells, but their "oiless" compressors are horribly loud. Be sure you can handle the noise before buying one.

Don Mallinson
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I recently picked up one of these critters for $79.00 as an early
Christmas present for myself. Crap, this friggen thing kicks ass (can
I say "Christmas"?).

It feels like a kitten in your hands when it's working - you can
easily work with it one handed even on it's highest setting - I can
only figure that is the twin hammers opposing each other and
cancelling out force. My older, weaker impact twists hard in
comparison - you need both hands when it bottoms out - but set at
highest output it doesn't even equal level 3 on the new gun which has
6 power levels.

Also, I fear level 6 at 95 PSI will rip out wheel studs.

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=2623
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97 Pacific Green - Parting this one Out
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We used mostly Chicago Pneumatic in my dad's shop, but he had one IR that worked well, so I would be looking to buy one of those brands. I've noticed some incredibly cheap impact tools for sale, and figured they were probably a waste of money.

Long ago I figured out that even though I was hooked on SnapOn for wrenches/sockets/ratchets, you didn't have to buy everything from the SnapOn guy. I bought some lesser tools, hammers and such, from Sears or wherever. I even bought some 3/8" drive extensions from Wal-Mart. I bought a Harbor Freight drill press, because I use it very little and mostly for light duty drilling. But I wouldn't buy a cheap cordless drill, and bought the best DeWalt I could find. For an impact wrench I would buy a good brand, but maybe just buy their basic model.

bjshov8
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My dad said that back when he did most of the work in his shop they set
their air compressor to 160psi and used impact wrenches for everything. (I
suppose that was good for productivity.) He said they had to rebuild their
wrenches frequently though.

bjshov8
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I use a 3-gallon 1HP portable Craftsman compressor for inflating tires
and the air blow gun. It works fine on the same 15A 110V circuit that
also supplies everything else in my tiny garage (incl. lighting). The
Sears website is getting slammed right now so I can't snag a link.
It's the one that was $119.99 a while back and is probably under $100
now.

I use an electric (not cordless) impact wrench for loosening stuck
fasteners and lug nuts. That one was about $30 on sale from Harbor
Freight and it does the job nicely. (It's especially useful for
spring compressors and alternator pulley removal.)

Many of the folks on this list have a need for more "serious" tools
than these, but I don't, and it sounds like you don't either, Tim.

I use a 3-gallon 1HP portable Craftsman compressor for inflating tires
and the air blow gun. It works fine on the same 15A 110V circuit that
also supplies everything else in my tiny garage (incl. lighting). The
Sears website is getting slammed right now so I can't snag a link.
It's the one that was $119.99 a while back and is probably under $100
now.

I use an electric (not cordless) impact wrench for loosening stuck
fasteners and lug nuts. That one was about $30 on sale from Harbor
Freight and it does the job nicely. (It's especially useful for
spring compressors and alternator pulley removal.)

Many of the folks on this list have a need for more "serious" tools
than these, but I don't, and it sounds like you don't either, Tim.

Dan Carman
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I use thise one hard mounted in the garage. I removed the wheels and mounted
it on a rubber mat to a piece of 4x4 board from plant my mom's boyfriend
works in. The board comes from crates they get parts in and is made to take
300lbs. I use the same style of board cut up to place my jack and jack
stands on so they do not dig into the pavement of the driveway or damage the
concrete of the garage floor.

Built a baffle around it to keep the noise down and teed the out coming
line. I used the same pipe we had at the garage, bought it from the same
local company that maintains shops air lines and hoists. One side gets full
psi output to 4 different quick disconnects around my garage, the other 3
side goes in the house and down to my Railroad work bench with a regulator
on it to keep the psi down to 6-10 for my airbrushing of my modelling
projects.

Clare
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A small compressor will be fine for removing one nut. The CFM rating is for ‘staying power’ or running more than one tool at a time. Make sure it puts out 125 psi. Spend the money on the impact wrench. If it cost less than $200, don’t bother

Paul L Fisher
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It’s not the tank size, it’s the compressor capacity. To get 5 scfm @ 90 psi takes a certain size compressor motor. The tank will determine how long you can maintain the 5.0 scfm. For certain tasks like a paint gun or a sander, the volume of the tank matters. For an impact, you need the power to have it do it’s work.

Ron Porter
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That's the gun I've got. I was going to get the IR Thunder Gun, but I cheaped out
and got the Earthquake for half the cost.

It has done all that I've asked of it over these past two years, and it was
worth the $$$.

FWIW, I always use level 6 to remove lug nuts, then I use level 2 to install
lugs (just under 100 lbs/ft) for the cars, and level 3 (just under 150 lbs/ft)
for the truck that takes 150 lbs/ft for the 8 lugs.

Ron Porter
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It's got to be some of each. If the wrench develops power at 90psi, and the tank contains more pressure, and the motor is not running, the wrench will run until the pressure coming out of the tank drops below what the wrench needs to run. With a small tank, it might only run the wrench a couple of seconds. My dad runs a pretty big tank in his shop, maybe 100 gallons. You can run a wrench for a long time before the motor kicks in. The motor runs a minute or so to bring the tank back to pressure then shuts off. Then you run the wrench for quite awhile before the motor wants to come on again. I would think a small tank would work the same way, but the motor would have to come on more frequently and you'd have to stop and wait for it to come back up to pressure. With my dad's setup you can keep running your wrench while the compressor is running. With a small tank and small compressor you probably couldn't
bjshov8
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Yep. Full set of torque sticks, 60 ft lb to 150 ft lb 1/2" drive. We even
have one that does 475 ft lb (1" drive) for our GMC C5500 trucks we work on.

Paul L Fisher

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Mine is a MAC tools AW434 Series from about 14 years ago when I bought it
brand new.
I only use it to remove nuts. All whee nuts here get the speed wrench then
my 3 foot long Mac torque wrench to tighten up.
IT will snap a grade 8 1/2 inch dia bolt right in half on its highest
setting.

Never had a bolt or nut I could never get out.

It and my MAC tools air ratchet move some much air that they blow stuff
across a work bench.

Neighbours can hear me fire both up. Not that I do as much as I used to.

Clare

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