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What Size Air Compressor?
#1
I have a Crafstman 2Hp, 6 gallon, 150PSI pancake style compressor. My air tools only last about a minute of use before I have to wait for it to build up pressure again. It's a real PITA!

Should this be good enough to work the grinder and other garage air tools or do I need to upgrade to a Higher Volume Tank like a 20 gallon?
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#2
(12-27-2010, 05:14 PM)f117rt Wrote: I have a Crafstman 2Hp, 6 gallon, 150PSI pancake style compressor. My air tools only last about a minute of use before I have to wait for it to build up pressure again. It's a real PITA!

Should this be good enough to work the grinder and other garage air tools or do I need to upgrade to a Higher Volume Tank like a 20 gallon?


well the larger the tank the better. I started out with the same pancake compressor you did.
the problem is it only delivers 3-6 SCFM @ maybe 40 pounds and under 3 at 90psi

most air tools require 90 PSI so you want to have a higher rating at 90 in SCFM. SCFM means Standard cubic feet per minute.

so a unit rated at 3 SCFM @ 40 means you have 3 minutes or less of usable time before the tank will be below 40 PSI.

at 90 you will be lucky to go 1 minute before your under 90 the compressor motor will flip on long before that but will not be able to keep up.

basically i found those 6 gallon pancake compressors are good for not much, low work cycle like using a nailer or flushing out water pipes for underground systems. you will not be able to use them for painting since they run out of air very fast.

my next step up was a twin stack 4.5 gallon compressor that was rated at
4.9 SCFM @ 90 psi. this gave me at least 4 minutes of air and was a pretty good compressor i was able to run a Media blasting cabinet just barely and got through a lot of my first projects with it. however once again 4 minutes isn't a whole lot of time.

home depot had a clearance sale and i went to a 60 gallon 3.2 HP that claimed 11.5 SCFM at 40 psi and 10.2 SCFM at 90 psi. i would get about 6-8 minutes at 90 with the regulator set i had to install a 220volt line to the garage to use it, and it made using my media blaster cabinet even better. however i found myself overloading it and popping fuses after extended use. plus it was super noisy.

in my opinion its still insufficient and you get what you pay for.

I've found if you want a truly shop ready air compressor you have to spend at lest 2000$ then your talking 23.7/22.2SCFM @ 90/175 PSI.
hey almost a 1/2 hour of continuous air is AWESOME.


The truth is there are very few air tools worth using, and the electrical versions will provide all you need and cost less. if your going to use a grinder get an electrical version it will provide better continuous torque and it won't drop off power like a air version. granted it will be a little bulky compared to the air version but i found the air hose gets more in the way then the electrical cord, and i liked the convenience of just shutting a tool off and not dealing with maintenance on the air tank and the tool itself buying oil and making sure to constantly clean the water trap.

as tools get better and batteries improve i find air tools just fading away, i went through both air and powered tools and found the power tools worked better for most things. also the noise reduction of not having to have the compressor firing in addition to the tool making noise was better.

if you have a good compressor then;
Air tools that shine: the impact wrench, paint sprayer, media blaster, nailer.

air tools that didn't live up: grinder, cutter, saw.


the problem is to really make air tools work you need a serious shop compressor and you will need to either build a shed for it or a closet to put it in to muffle the noise then you need to route air lines around the shop with quick connectors so its just like plugging in a tool to the electrical outlet. but if you spend all that crazy money to do that and you only need to use it once in a blue moon, then its pointless and your better off with electrical tools for 90% of the work.
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#3
Guess what I got for christmas? Yep, an air compressor. Up until now, I had every type of tool that went around in circles plus a reciprocating saw (two of those). From a Dremel, to a RotoZip (two of these), to an angle grinder (a 4" and a 6"), three drills (one battery, one variable speed and my favorite - variable speed close quarters drill).

It's a Craftsman 12 gallon, 1 Hp, 125 psi 2.4scfm @90 psi. Fired it up tonight and couldn't figure out why I was loosing pressure so quickly. Got out the old spray bottle and found a quality control problem. One of the welds to hold the feet on the tank welded right through the tank.

Just found gift receipt and am headed back to sears on Tuesday. Will give report when tank is fully operational...

1973 Mach 1 - Medium Bright Yellow - (in restoration mode)
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#4
The air compressor is theheart of every shop. Don't skimp here. Buy the biggest and best that you can if you are going to do any serious work. I have an 80 gallon and it still has a hard time with what I am doing.
1972 Mach 1
Q-Code
Under full restoration

[Image: IMAG0050.jpg]
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#5
(12-27-2010, 06:52 PM)72HCODE Wrote:
(12-27-2010, 05:14 PM)f117rt Wrote: I have a Crafstman 2Hp, 6 gallon, 150PSI pancake style compressor. My air tools only last about a minute of use before I have to wait for it to build up pressure again. It's a real PITA!

Should this be good enough to work the grinder and other garage air tools or do I need to upgrade to a Higher Volume Tank like a 20 gallon?


well the larger the tank the better. I started out with the same pancake compressor you did.
the problem is it only delivers 3-6 SCFM @ maybe 40 pounds and under 3 at 90psi

most air tools require 90 PSI so you want to have a higher rating at 90 in SCFM. SCFM means Standard cubic feet per minute.

so a unit rated at 3 SCFM @ 40 means you have 3 minutes or less of usable time before the tank will be below 40 PSI.

at 90 you will be lucky to go 1 minute before your under 90 the compressor motor will flip on long before that but will not be able to keep up.

basically i found those 6 gallon pancake compressors are good for not much, low work cycle like using a nailer or flushing out water pipes for underground systems. you will not be able to use them for painting since they run out of air very fast.

my next step up was a twin stack 4.5 gallon compressor that was rated at
4.9 SCFM @ 90 psi. this gave me at least 4 minutes of air and was a pretty good compressor i was able to run a Media blasting cabinet just barely and got through a lot of my first projects with it. however once again 4 minutes isn't a whole lot of time.

home depot had a clearance sale and i went to a 60 gallon 3.2 HP that claimed 11.5 SCFM at 40 psi and 10.2 SCFM at 90 psi. i would get about 6-8 minutes at 90 with the regulator set i had to install a 220volt line to the garage to use it, and it made using my media blaster cabinet even better. however i found myself overloading it and popping fuses after extended use. plus it was super noisy.

in my opinion its still insufficient and you get what you pay for.

I've found if you want a truly shop ready air compressor you have to spend at lest 2000$ then your talking 23.7/22.2SCFM @ 90/175 PSI.
hey almost a 1/2 hour of continuous air is AWESOME.


The truth is there are very few air tools worth using, and the electrical versions will provide all you need and cost less. if your going to use a grinder get an electrical version it will provide better continuous torque and it won't drop off power like a air version. granted it will be a little bulky compared to the air version but i found the air hose gets more in the way then the electrical cord, and i liked the convenience of just shutting a tool off and not dealing with maintenance on the air tank and the tool itself buying oil and making sure to constantly clean the water trap.

as tools get better and batteries improve i find air tools just fading away, i went through both air and powered tools and found the power tools worked better for most things. also the noise reduction of not having to have the compressor firing in addition to the tool making noise was better.

if you have a good compressor then;
Air tools that shine: the impact wrench, paint sprayer, media blaster, nailer.

air tools that didn't live up: grinder, cutter, saw.


the problem is to really make air tools work you need a serious shop compressor and you will need to either build a shed for it or a closet to put it in to muffle the noise then you need to route air lines around the shop with quick connectors so its just like plugging in a tool to the electrical outlet. but if you spend all that crazy money to do that and you only need to use it once in a blue moon, then its pointless and your better off with electrical tools for 90% of the work.

Thanks for the advise!
What you steted makes sense.
I guess I'll use the money I was going t buy a bigger compresser on electric tools
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#6
Check E-bay or craigslist. Another good place is watch for auctions.
I got lucky, a friend of mine has a body shop and he was upgrading his compressor. I picked up his old one for $300. Will post pic of it tomorrow.
jim
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#7
This is the air compressor that I scored for $300


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#8
Although the person that gave me the Craftsman 1 hp 125 psi compressor had the best intentions for me, the previous post regarding SCFM is of great assistance. The smallest rotary air tool I picked up uses 6 SCFM at 90. The 1hp just didn't do it. Like they say, go big or go home. Start with at least 2-1/2 hp and go up from there for any real work. Since, I'm knee deep in electrical grinders, drills etc. I returned the compressor for refund.
1973 Mach 1 - Medium Bright Yellow - (in restoration mode)
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#9
Agreed the bigger the better. How much you use it makes a difference on the quality of compressor.
Jeff T.

Low buck, touring style, '73 Convertible "rolling restoration", 351c, 2v heads with a shave and a haircut, Performer intake, Holley 650(ish), roller rockers, screw in studs, guideplates, stainless valves, Duraspark / Motorsports MSD, T-5 conversion. 1-1/8" front, 3/4" rear swaybars KYB shocks and some home brewed subframe connectors. Future plans; JGC steering box, Cobra brakes and... paint, interior, etc.

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passenger.

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#10
another thing to watch out for is the duty cycle of the air compressor.
you can have a 400 gallon tank if the duty cycle is like 10% your in for a world of hell.

the best type is a screw type compressor with 100% duty cycle, that means you could run it 24 hours a day at 150psi and maintain pressure.

at work i have such a compressor of course its a 10,000$ unit lol and would take up about 1/8 of my garage, so its not practical for the home hobbyist.

basically look at how long the compressor can maintain 90 PSI the larger the SCFM the better, next look at the duty cycle of the compressor if listed the closer to 100% the better.

220 is better then 120 volt
more horsepower is better
and the larger the tank the better as it can compensate for a lower duty cycle.
next the more cylinders the better.
if your serious you need to look at a water trap or even better a refrigerator unit with filters and water trap, now your talking an extra 1000-2000$ but if you do any media blasting work you must have one.

as said go big or go home.

the other option is just get electrical powered tools that do the same as the air tools.
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