Looking on feedback on impact wrenches--corded, cordless, pneumatic

cigroller, you said, “I have an impact that tells me that it will do 525 ftlb. However, I’m assuming that getting the full power from it requires the right oomph from the compressor - or does it not?”

You need to google the make & model # of your impact tool, & get the average air consumption spec & also the “air consumption at load” (max momentary air consumption). For example, my CP 7750 1/2" drive air impact wrench, w/550 ft lbs of normal working torque, 800 ft lb rating for breakaway torque, has an 8 CFM average air consumption rate, & 32 CFM air consumption at load rate, so, to power that gun one would need a compressor with at least those CFM ratings, plus every 1/2" drive gun I’ve ever seen needs a minimum of 90 psi AT THE GUN, which is more like 110-120 PSI coming out of the compressor. But believe me, as you find more chores the compressor can do, you may wish you had chosen one with a greater CFM rating than what you would need with just an impact wrench!

Hope this helps. Please let everyone know what you end up doing.

P.S: Go with a 3/8" I.D. air hose instead of the 1/4". This will allow the compressor to flow enough CFM’s. Also, the coupler plugs that push into the coupler on the end of the hose are the most narrow part of any air system & are the weak link as far as enabling compressor flow. Milton makes high flow “v style” coupler plugs; see p. 42 of this website:


@karl_sieger - that was very helpful. Thanks very much. So in short, it seems, you need a minimum PSI, but the key for hitting the full tool capacity is CFM. My impact is just a Kobalt that I picked up from Lowes. For a long time I just had a little 4 gal pancake compressor on loan from my brother. I don’t even know what its CFM rating was, but it did fine with the Kobalt 90% of the time. The only thing that stymied the set up was an axle nut that I ended up taking to a shop to have broken loose.

But my brother had to take his compressor back - so I do need to get a new one. The problem is that I don’t use it very often (so breaking the bank makes no sense), but do use it for lots of different things (so doing without one entirely will never work). Unfortunately I don’t think I’m going to be able to end up with something that even does 8CFM - let a lone 32. But I suppose there are always going to be those times where you need another way to skin the cat.

Thanks again.

It’s interesting that the Meanjoe wants to bust loose frozen ball joint nuts, and yet, no one mentioned that it’s very, very difficult to get a real impact in that cramped area. I don’t know what you’re driving, but I"m positive I can’t get one on either of my vehicles, nor any of the vehicels I’ve workied on…there just isn’t enough room.

Of course, there are many, many good reasons to have an impact. Ball joint nuts just isn’t the one.

I’ve always gone with sturdy (I use almost all impact stuff) sockets and a long breaker bar. The shorter the socket on the nut, the more force directly applied to loosening it, and less to twisting the socket off the nut. If you do use an impact, you’ll also want impact extensions, sockets, and maybe even swivel extansions to bust those loose.

For really stubborn ones, I’ve also found that keeping a good pressure on the breaker bar and then using a hammer for impact-type of force works well in some circumstances. If you’re not trying to keep the ball joint, consider heat, too. heating up the nut (and avoiding the center if possible) will also help break those loose. Just watch out for fires. :slight_smile:


It’s interesting that the Meanjoe wants to bust loose frozen ball joint nuts, and yet, no one mentioned that it’s very, very difficult to get a real impact in that cramped area

Because most of the advice to buy air tools was dispensed before Meanjoe specified ball joints. The first post just said fasteners under the car.

cigroller, if you can swing $500, here’s one with pretty good specs:


Worn sockets will greatly reduce the effectiveness of an impact. For best results the socket should be a snug fit on the hex and the square drive mating must also fit with no play.

I don’t care for cordless stuff because the battery life is going to be short when dealing with rusted, tight, or larger fasteners. Unless you’re keeping a slew of charged batteries around to swap as necessary.
Corded impacts are better but are going to struggle, maybe with no success, on larger fasteners.

I’ve got several corded impacts and they simply cannot do what a good pneumatic unit will and as to ratings I think many of those ratings are overblown by the manufacturers of those tools. In a nutshell, they’re puffing the numbers a bit just like a car maker puffing horsepower numbers, etc.

cigroller, A compressor that can supply 5 or 6 CFM @ 90 PSI will usually do pretty good for shadetree stuff. If you have a 3/8 ID hose, any compressor will run an impact wrench, as an impact wrench usually isn’t run for more than a couple seconds at a time. If my (17 gallon) tank has 130 PSI in it, I can take 2 wheels off my car and put them back on without plugging the compressor into the wall outlet.

I can understand the concern for a professional mechanic to be concerned with battery life…but for the back-yard mechanic it makes more sense then buying a compressor and air-ratchets.

As long as you’re just yanking wheels, sure. Try going after a crank pulley bolt with a cordless impact wrench and see how far it gets ya :wink:

I spent 2 hours one time trying to remove 4 spark plugs from a poorly running Subaru in which those 4 spark plugs had just been installed a few days previously by an independent shop a few miles away.

Three pneumatic wrenches (2 of mine, 1 borrowed), 1 broken 1/2" drive Craftsman breakover, and a 3/4" drive breakover later I had them out.
There’s not a cordless or cord type on the planet that would have touched this job and even the penumatics would not bring them out.
How the shop wedged them in that tight I will never know.

Once out I found 3 different types of plugs had been used; 2 ACs, 1 Bosch, and 1 Champion. Apparently the indy shop was cleaning the back room out during their tune-up special… :wink:

Price is kind of an issue with these things, so try Harbor Freight Tools and buy their plug in model for price. Keep in mind that a $130 compressor is great for cleaning filters on bagless vacuum cleaners, so it will always be of use.

I’m sure it’s been said, but IMO if you are going to do this stuff very often, a compressor is the first and ultimately the cheapest way to go. Even moderately sized ones are good deals compared to an electric impact wrench that will last. Bite the bullet and just do it. I did it many years ago and even know when I seldom use it, it’s invaluable and pays for itself over and over.