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Unread 01-26-2013, 10:10 PM   #1
the88thpianoman
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A riddle of air compressors...

Comparing these two air compressors from harbor freight. They both have the exact same 2.5 hp motor and 125 psi rated tanks:

http://www.harborfreight.com/air-too...sor-67708.html

http://www.harborfreight.com/air-too...psi-67847.html

Yet, the 21 gal is rated at only 4.7 scfm, but the 10 gal is rated 5.3. Is there any reason why the larger tank should supply less air?

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Unread 01-26-2013, 10:46 PM   #2
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Quote:
Originally Posted by the88thpianoman View Post
Comparing these two air compressors from harbor freight. They both have the exact same 2.5 hp motor and 125 psi rated tanks:

http://www.harborfreight.com/air-too...sor-67708.html

http://www.harborfreight.com/air-too...psi-67847.html

Yet, the 21 gal is rated at only 4.7 scfm, but the 10 gal is rated 5.3. Is there any reason why the larger tank should supply less air?
The supply is what is available from the compressor, and has nothing to do with the storage tank.

Obviously, the two compressors are different - and it's fairly common for a lower-pressure compressor to have a higher volume delivery (just as in electricity, pressure and volume delivery are directly mathematically related.)
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Unread 01-26-2013, 11:17 PM   #3
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For 30 dollars more, I would just buy the bigger one. They are the same brand with the same motor. I doubt one is actually better than the other.

If you like your compressor turning on after on squeeze of an air gun trigger then get the smaller one.
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Unread 01-27-2013, 02:32 PM   #4
Baitis
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I doubt you'll notice any difference. Go with the bigger tank so that you won't have to listen to thing run as often. If you're looking to run any type of air tool neither will get the job done.
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Unread 01-27-2013, 07:13 PM   #5
1ironwill
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Neither. An air compressor is not a harbor freight purchase. What tools are you trying to use with it, and frequency of use?
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Unread 01-28-2013, 05:39 AM   #6
gmiller0737
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Neither. An air compressor is not a harbor freight purchase. What tools are you trying to use with it, and frequency of use?
This,While some things from H.F. are just fine their electrical stuff usualy dosen't hold up well.
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Unread 01-28-2013, 07:36 AM   #7
vadslram
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I have the HF pancake tank compressor that I use the bejeebers out of. My main compressor is a twin cylinder 2 hp with a 15 gallon tank but being 220v it is a bear to move around. The little one will do nailing, tire inflation and blowing down the irrigation for winter. I only need a 10 ft hose because it weighs nothing and runs on any 110v outlet so I bring the compressor to the work.
If you plan on making a living with pneumatics or plan on doing some serious custom painting you might want a bigger unit but for basic daily air the HF works fine. And if you think you need all the CFM for any lentgh of time GO 220v. 110 will be stressed in the long run, have work harder on startup and use more electricity.
I paid $39 for my pancake 4 yrs ago and it is still going strong.
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Unread 01-29-2013, 12:25 AM   #8
the88thpianoman
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Originally Posted by 1ironwill View Post
Neither. An air compressor is not a harbor freight purchase. What tools are you trying to use with it, and frequency of use?
It wouldn't be a HF purchase if I needed a heavy duty one, but for airing up tires, occasionally zapping off some lug nuts, and every once in a while going at a control arm bolt, I think this will do just fine. I've heard pretty bad things about non-oiled HF compressors, but pretty good things about the oiled models.
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Unread 01-29-2013, 04:30 AM   #9
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I doubt that either one will run an impact gun. I have a oiled compressor that is rated at 5.7 SCFM at 90 psi and it won't run an impact gun that claims to need only 4.5 scfm at 90 psi in its specifications. Unfortunately you really need a two-stage compressor to run tools like an impact gun effectively.
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Unread 01-30-2013, 05:52 PM   #10
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I bought a 12 gallon air compressor from sears and it's only 2.4 cfm and it wont run my die grinder for more than 30 seconds. My ginder uses abour 3 cfm at 90 psi. My impact doesnt really matter since it's massive air and storage capacity is more important. Do I wished I would have gone bigger. I have been looking into this one. http://www.harborfreight.com/2-horse...8127-8026.html Supposed to be a lot quieter being belt driven and puts out almost 6cfm. Another hundred bucks would get me a 60 gallon from home depot, but dont know if it's worth it. Does the 20% off cupons work for air compressors they send you in the mail all the time?
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Unread 01-30-2013, 06:20 PM   #11
joeyk803c
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It should.

My dad picked up a 3 gallon HF compressor a few years back for $70. It has a higher SCFM rating then our 33 gallon Husky compressor. We had an issue with the auto switch, but my buddy fixed that in a second. It works just fine. Hell I used it when I was replacing the shocks on my TJ the other week. Ran my CH 1/2 Impact gun fine.
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Unread 01-30-2013, 06:45 PM   #12
the88thpianoman
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Originally Posted by That1guy View Post
I bought a 12 gallon air compressor from sears and it's only 2.4 cfm and it wont run my die grinder for more than 30 seconds. My ginder uses abour 3 cfm at 90 psi. My impact doesnt really matter since it's massive air and storage capacity is more important. Do I wished I would have gone bigger. I have been looking into this one. http://www.harborfreight.com/2-horse...8127-8026.html Supposed to be a lot quieter being belt driven and puts out almost 6cfm. Another hundred bucks would get me a 60 gallon from home depot, but dont know if it's worth it. Does the 20% off cupons work for air compressors they send you in the mail all the time?
No the compressors are excluded from the coupons.

I'll be testing out the 21 gallon compressor this weekend. My impact wrench is rated for about 5 scfm @ 90 psi. I really don't mind if I have to wait in between trigger pulls on the impact wrench. I won't need to use it much right now and I don't have the budget for a nice compressor. If it works at all, I'll be happy. It's mostly going to be used for airing up tires and blowing dust out of computer parts.
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Unread 01-31-2013, 03:48 AM   #13
vadslram
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Quote:
Originally Posted by the88thpianoman View Post
No the compressors are excluded from the coupons.I'll be testing out the 21 gallon compressor this weekend. My impact wrench is rated for about 5 scfm @ 90 psi. I really don't mind if I have to wait in between trigger pulls on the impact wrench. I won't need to use it much right now and I don't have the budget for a nice compressor. If it works at all, I'll be happy. It's mostly going to be used for airing up tires and blowing dust out of computer parts.
Not at my HF. Everything is included but sale items.
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Unread 01-31-2013, 07:18 AM   #14
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you shouldnt have to ait between trigger pulls.
im using a 5 gallon compressor my fathers had for many many years for carpentry and roofing.
and i can lay on the trigger for a good solid minute straight before the compressor kicks back on.
but it has alot of trouble with lug nuts. (i also use about 130ftlbs for them, but still)
so with 21 gallons, i think your only concern should be whether it can put out the power you need.
im using a kobalt 1/2" rated for 300ft-lbs at 90psi. not sure of these other numbers being discussed, dont even know what those mean to be honest
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Unread 01-31-2013, 07:51 AM   #15
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I have a drawer full of air tools I never use any more. A quality electric impact is a lot more handy.
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