I have a craftsman 1/2 inch impact wrench, i'm using a 5hp compressor with a 30 gallon tank. I can't even take off the lugnuts on my car with ut lossening them first.I'm not sure if it's my compressor or the impact wrench.(i'm using about 40ft of 3/8 inch hose)

Pneumatic tools are rated in cfm (cubic feet per minute). Your 1 HP air compressor is rated at probably not more than 3 cfm while the 1/2 " impact driver needs at least 8 cfm, maybe 12 chm of air.
The compressor must provide more chm than tool rating needs.
It is a problem, by the time you look at five horse power air compressors and larger, a lot of electric power is needed. A circuit of 220 volts, 20, 30, or more amps would be required to run those large expensive compressors.
If you can, return the air tool and get a good electric tool instead.
Leave those high air volume air tools to shops that are so equipped to use, or invest if you must.

Mobile synthetic 10-30 , Craftsman compressor oil if K-mart or Sears are near by. You can also use a non-detergent 10 - 30 motor oil , I use Mobile or Craftsman in mine. I have three - one is a Campbell Hausfeld this oil is per their book - (minus the Craftsman)

Don F

The two most important specs are CFM at 90 psi (that's how fast the compressor can compress more air when the tank starts to run low) and how big the tank is. Virtually any compressor that has a top pressure rating 20 psi higher than you need for your tool (which is usually about 90 psi) and that has a tank of a couple of gallons will work. But the smaller the tank, the shorter time you can operate the tool before the compressor has to kick in. And the lower the CFM at 90, the longer you will have to wait for the tank to come up to pressure again so you can operate the tool at full pressure. If this is for occasional use and you aren't in a hurry, you don't need much of a compressor at all. If you want to operate continuously, then you should get something with a CFM at 90 psi that is higher than your tool's CFM consumption. Keep in mind that impact wrenches don't operate continuously like paint sprayers do. Good luck. Vote if you found this helpful. Al K

Hi and welcome to FixYa, I am Kelly.

Air Tool consumptions are based on 15 seconds per minute (25%) of tool use.

Usage rates refer to the total time that air is flowing through the tool. If your applications result in more extensive usage, calculate air tool requirements as

follows.

(25%) 15 seconds = rated scfm x 1

(50%) 30 seconds = rated scfm x 2

(75%) 45 seconds = rated scfm x 3
(100%) 60 seconds = rated scfm x 4

Your impact wrench is rated a 8 CFM Cubic Feet Per Minute Usage

SCFM is Standard Cubic Feet per Minute (pre-compressed air volume)

I would be more concerned that the plumbing from the compressor tank could support the 8 CFM required by the 1/2" Impact. Remember the Air compressor will recover the pressure loss regardless of size. The only problem your going to have for "small jobs" is if you use too small of an air line to supply the impact wrench you are not going to get the full torque that it will produce to the drive head. In other words... a 1/4" supply line or 1/4 fittings anywhere in the system just isn't going to cut it even at 120 PSI. If you have the patience... a 5 gallon tank compressor that has the output volume required should be all that you need. I have been a mechanic over 4 decades and rarely have to use a 1/2 in impact for very long. Examples of 1/2" vs 3/8" useage. Wheel nuts, crankshaft pulley center bolt, some starters, steering, suspension and rear end parts. Other than that a 3/8" Impact works great.

One other thing you can do if you have an Air-Peen portable tank (with added fittings) is to add that in line with your output hose when your using the impact wrench so that you have longer use times.

I know this does not answer your what SCFM compressor is required question but it will resolve your needs. I just can't see telling someone that is a "small jobs" user to buy a larger compressor when really all they need is more volume for a brief period of time. The re-plumbed 1/2 inch output / in-line Air-Peen tank is a much cheaper and reasonable work around and you can disconnect that tank when your not using the impact wrench.
Lastly... if your inpact wrench has a SMALL male air fitting everything above will be a waste of time. You have to get that volume into the tool without restriction so that the rool will work properly for you.

Thanks for choosing FixYa.
Kelly

first I hope that you drain the water out of the tank regularly. It seems as though you might have an air hose collapsing but in any case there is something apparently restricting air flow too the gun. try opening the petcock and see if you have steady air discharge or not and if you have another air hose try it. Also, are coming directly off the compressor to the tool or do you have an oiler or drier in line? if so, eliminate the accessory. Let me know how you do....I'm curious.

It needs to be taken apart and cleaned then lube it with air tool oil and reassemble it should make a big difference

You probably have a restriction in the regulator. You may be able to disassemble and clean it but you'll have to relieve the tank.

Make sure you have at least 90 pounds of air and if you do you need to oil the wrench air tool oil pour some in the where the air line hooks up ..air tools need to be oiled daily cause compressed air cause water vapors to build up when you use it and then when it sits it begins to rust a bit and the oil stops this ...

Here are the specs on your compressor:
Electric Single Stage Air Compressor, Motor Running Power 5.0 HP, Free Air Flow @ Maximum Pressure 16.1 CFM, Free Air Flow @ 90 psi 18.0 CFM, Maximum Pressure 135 PSI, Phase Single, Voltage Rating 230 Volts, Current Rating 21.5 Amps, Tank Capacity 60 Gallons, Tank Type Vertical, Height 71 Inches, Length 20 Inches, Width 30 Inches, NPT Outlet (F) 1/2 Inch, 60 Hz
Good luck with your new comressor.

An impact wrench also requires a few special accessories. An air-powered impact wrench runs off of an air compressor with a tank – the air compressor should have at least a 10 gallon tank and be able to generate at least 3hp. Also, an impact wrench requires special sockets that are designed to withstand the high torque applied by the wrench.