I have an old 1hp 3gal Craftsman that i use for various hobbies and delivers 2.4 SCFM at 90psi. Recently, i bought a $40 impact, also from Craftsman, rated at 340 ft. lbs and supposedly needs 4.1 SCFM at the same pressure. The set-up works fine, but it seems to struggle a little when taking lugs off (takes about 3-4 seconds to loosen a lug, out of the 5 second recommended maximum continuous use suggested in the manual.)

I'm a complete newbie when it comes to this stuff, so bear with me.

Is this a case of an underpowered compressor, or a weak impact? I'm sure some will say it's both, but what i can do to make the most out of this situation? Will replacing the impact with a better one help, or would i be better off with a larger compressor that can push more air? (I'm hoping it's the former)

I've read that the ideal setup is to get a compressor that's rated at 1.5x the cfm rating of the tool i'm using, or 6+ cfm. That sounds rather high, and compressors at this range costs quite a bit more.

Comments are gladly appreciated.

Thanks.

 

IR Impacts FTW.


but in your case I blame compressor............It's just too small.

 

Make sure your impact is properly lubed with air tool oil, both in the motor and the gearset.

A 3 gallon tank @ 90PSI doesn't give you any reserve at all - there's only a few seconds worth of air in the tank and it's right at the required pressure for the tool.
The compressor will never keep up. It's OK for a nailer, but for an impact - not so much.

 

Thanks, guys. The gun is well lubricated, at least as far as i'm concerned.

So it's the compressor? I don't mind the constant recycling and do like the portability of it.

However, i see y'all's point. If i do go for a new compressor, should i be looking for a larger capacity, or one that pushes more air? (e.g. 10 gallons at 3.4scfm, or 5 gallons at 4.2scfm.)

 

^^ If all you want to power is nailers and impact you can go smaller (not smaller than you have, just smallish rather than BIG) and more portable. The stuff that takes the most air are paint guns, sanders and grinders. I bought a Craftsman on sale a couple of years ago - 6.3 SCFM @ 40psi, 4.9 @ 90psi, 150psi max and a vertical 33 gallon tank.

 

+10000000

ir 2135ti ftmfgdw!!!!
-gp-

 

I'd like to eventually use an airbrush with it, and i've heard those use a lot of air as well. I'll check out the larger tanks and weigh in the pros/cons. Thanks, Coach.

 

bare minimum is a 30 gallon tank if your using air impacts,drills,ratchets or any length of continues on time tools, I have a 33 gal compressor and it comes on every 3 to 5 min's at 90 psi, I havn't looked in a long time but there are some higher pressure rated system at the same tank size's so check those out too.

 

Hmm... so really, i should be looking at tank capacity and not how much air is pushed at 90psi? Again, i don't mind the recycling, but it just feels like the impact isn't putting out much torque. I originally thought it was because it's rated higher than what my compressor can push out.

To get a compressor that barely meets the requirements of my $40 impact would require buying a $600 compressor.

 

If the max in your tank is 90 psi and the rated requirement for your tool is also 90 psi you have zero buffer - as soon as you draw any air from the tank then the pressure in both your tank and hose is dropping below 90 psi and the tool loses power. If the tank is only 3 gallons, it takes only a couple seconds before your tank is down to 40-50 psi.

On the other hand, if the tank is 30+ gallons and starts off at 150 psi, you can draw air for quite a while at 90 psi hose pressure before the tank gets down to 90 itself (the compressor would kick in before it got there). Your compressor doesn't have to keep up with the tool all the time if the tank size and max tank pressure are enough to give you the buffer you need to operate the tool.

The only time the compressor has to have air volume output in excess of the tool requirement is if you have a constant flow, like a grinder or paint gun that doesn't give the tank any downtime to refill.

Unfortunately a $40 impact takes just as much air as a $400 impact. I don't think you need to spend $600 though, if you're not looking for commercial grade you could get what you need for half of that. I got the one I described above for $350 CDN.

 

Thanks for the further explanation. Much appreciated.

The compressor is rated at 125 PSI, i was just noting the SCFM at 90psi between that and the impact. All the while i thought the numbers had to match as close as possible.

Based on your comment above "Your compressor doesn't have to keep up with the tool all the time if the tank size and max tank pressure are enough to give you the buffer you need to operate the tool." it looks like i shouldn't really worry about the SCFM rating, at least for the tools i currently have.