What to look for in an Impact Wrench?
 

My 15 gal. air compressor has the following specs:

SCFM Delivery:
SCFM Delivery At 40 psi 4.9 SCFM
SCFM Delivery At 90 psi 3.5 SCFM

Most impact wrenches I'm looking at consume 4.5 - 6.5 SCFM. Getting a new air compressor is not an option right now. Can I use a 6.5 SCFM impact wrench with my air compressor?

Any compressor that puts out 90 psi will be just fine for an impact wrench, and you don't have to worry about the continuous delivery aspect of your compressor at all (unlike using a paint gun, grinder, etc.).

Also, do I really need an impact wrench that can go to 600 ft./lbs. of torque? Am I fine with 300 ft./lbs.?

I never use an impact wrench on my car except for a couple of places where it just makes sense (i.e. shock tower bolts). When I do pull out my impact, it's typically to break something loose, so my Ingersol Rand (with over 600 ft/ lbs) really comes in handy. I'm a weekend warrior, but I had a couple of pro wrenches tell me not to waste $ on lesser wrenches, and go with the I/R so that's what I did. That being said, my I/R wouldn't budge my engine mount bolts the first time I removed them (but it did have enough torque to snap my crossmember :)) whereas a 3' breaker bar (section of pipe) worked like a champ. Honestly, if it were me, I'd stick with sections of pipe rather than get a wrench that won't do the tough jobs. I've loaned my I/R to a buddy when his wasn't getting the job done, and he was looking to buy an I/R the next day.

more power isn't always better, I use my 3/8" drive butterfly throttle valve air impact on light duty jobs all the time, then pull out the big 1/2" impact when torque is needed.

The problem is the tool was designed for some volume and pressure so if you can't provide them the tool simply doesn't work. It may turn free but with no guts to undo anything, basically the tools can't give a lower torque by a restricting the input. - Ask me how I reach that conclusion... ;)
Kind of using your car with 50% water in the fuel tank, it just doesn't work.

You can rent a compressor at HomeDepot or other places..

With a 15 gallon tank at 150 psi, I'd assume that it could supply 6.5 SCFM @90 psi for some amount of time before the flow and/or pressure drops off. I can't really envision using it for more than a few seconds at a time.

I bought this one a month ago (on sale for $99 at the time). a bit lighter than most and 580 ftbls of torque. seems to be a quality piece...

http://www.sears.com/sr/javasr/product.do?pid=00919984000

Piggy back another 30 gal tank. With the larger reserve, you can pretend you have a better compressor. ;)

You can still run out of air, but not as soon. You may get all four wheels off instead of taking a break after each one.

That was actually one of the ones I was looking at. It's on special for Craftsman Club members at $109

Here's a nice one. I think it sells for about $250 off the Snap-On truck.

http://cgi.ebay.com/ebaymotors/Snap-On-Bluepoint-1-2-Air-Impact-Wrench_W0QQcmdZViewItemQQcategoryZ43988QQihZ006QQi temZ160140870193QQrdZ1QQsspagenameZWDVW

My buddy borrows my IR 2135 impact wrench (700ft/lbs) when his Snap On wrench won't do the job. It's got 4 click adjustment for power so you don't have to use more power than you need.
A "cheap" impact wrench is kinda useless. (But I find other "cheap" air tools work just fine.)
An impact wrench is not a butchers tool if used right.
One thing you don't want to use it on is axle nuts unless you are replacing the wheel bearings.
-Chris

i think a good IR & 3/8" hose is worth a shot.

Exactly.

A real plus with these high torque wrenches imo...

Air Impact Wrench, 1/2 inch Titanium Duty
Pound for pound, no other gun even comes close to the power and performance. The first time you pick it up, you'll see and feel the difference. It all starts with Titanium, which allowed us to create a compact 1/2 inch design that offers unbeatable strength and durability, yet weighs just 3.95 pounds for less fatigue after a long day.

* Titanium weighs less, provides greater durability.
* Enhanced Twin Hammer impact mechanism for fast removal of frozen bolts
* Contoured composite butterfly throttle for comfort and control.
* Professional touch trigger for ultimate power control.
* 7-vane motor delivers 1,000 foot pounds of Nut Busting Torque and 700 foot pounds of traditional torque output.
* Four-position power management control.
* Push button forward/reverse controls for one-handed operation.
Ergonomic handle design for comfort and improved grip control.
* Through-handle exhaust; 360-degree swivel inlet.
* Ultimate Torque: 700 foot pounds.
* Average Air Consumption: 5 CFM
* Free Speed: 9,500 RPM
* Weight: 3.95 poundshttp://forums.pelicanparts.com/uploa...1185539410.jpg

The beast :)!

Get the most powerful one you can afford, you'll thank yourself. Dont buy snap-on or mac, just go buy yourself a new CP or IR (same thing) and save a bucketful of money.

What's the purpose? To remove stubborn fasteners are to speed up a repair job? IMHO, you need both.

Amazing how much time is spent manually rotating a threaded fastener after loosening it. For fasteners that require a 13mm or smaller socket, I often use a 1/4" dr. air ratchet handle to manually loosen the fastener, then use air to remove it. It's compact, lightweight, easy to handle and won't fatigue your arm and wrist as much as the larger guns. A ti ratchet and lightweight air hose would be nice.

Sherwood

I do have an air ratchet. I use it mostly for loosening. I like to hand tighten and then use a torque wrench so as not to strip bolts.

I want an impact wrench for automotive and other general around the house work. I borrowed my neighbors electric impact wrench for disassembling my deck (many carriage bolts) and it made it a breeze.