[Computerworks]

For those that have an air compressor in their shop or garage:
What are the specs to look for?
What's the difference ( or significance) between oil-lubed and non-oil?
I have looked at small portables (25-gal) and larger-tanked fixed units (60-80-gal)... what are the pro's and con's
Anyone pleased with a certain make and model?

I will be using it for shop tools - no painting.

All input is appreciated.

 

[TAZ]

Ron,

Three factors.

Noise: Lubed ones are preferred, because they are quiter but are more intricate and cost more money (but will last longer if you keep them lubed.) I personally went with a direct drive unit (non-lubed) It's loud, but I can live with it. I'm considering building a box with sound insulation around part of it.

Capacity: The biger the tank the better, I'd say 30 Gal is typical descent size for most garage work. If you got a unit that is 25-40 Gal you should be fine as long as you're pump can also keep up. I've used mine w/ a sandblaster and it keeps up. Air drills and ratches will use a fair amount of air but a 30Gal w/ about 6 CFMs at 90 PSI should do the trick. You only really need to go to large capacity if you're feeding multiple work areas and you have several tools in use at once from the same tank. But don't buy one of those dinky assed 2.5 gal jobs like a friend of mine did.

CFMs: How much air can you pump at 90PSI when operating a tools. I'd say don't get anything less than 6 CFM at 90psi, but you should never need anything greater than 9 CFMs at 90psi even if you want to try your hand at painting. Streetrodpainter - what do you require for painting?

Personally I'm using the Sears Craftsman 30Gal, 8.6 CFM at 40psi, 6.4 CFM at 90psi direct drive compressor. It can pump up to 150 psi, but I've got mine set to kick off at 135 to give it longer life. It's somewhat portable if you really need take it some place. Sears has it on sell for $299 and are tossing in an Impact Wrench and Air Ratchet as well.

Have fun with your air tools

TAZ

[ November 18, 2002, 05:46 PM: Message edited by: TAZ ]

 

[Colonial Cobra]

If your going to be using it a good bit, Go with an oil lubed unit. They tend to be a bit more expensive but will hold up longer.
5hp 30 gal. is a good all around compressor.
Much smaller and you will have trouble using high air demand tools like Grinders, sanders, and air ratchets.
Be sure to get an air line drier with it.

Brad

 

[bill32]

When I started the build I upgraded from my old Sears 100 PSI unit. The old one didn't have enough reserve or pressure for good use. I picked a Porter Cable (exact same as its Sears model) 30 gal upright, 175 PSI, $300. This works very well, has good reserve capacity, easy to adjust output pressure, is quiet, non-lube type. I got the Porter Cable instead of the Sears because it was on sale at Lowes at the time.

 

[Cobra Jones]

This has been covered a lot. I did a search for you using "Air" and "Compressor" as the search criteria. Here you go:

http://www.ffcars.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000913
http://www.ffcars.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=001314
http://www.ffcars.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=002517
http://www.ffcars.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=003882

Here's one of my old posts on this topic from June 2002:

"Here's a start to get some info. As with most things, there's seldom a simple answer:

www.kmstools.com/pages/compressguide/index.htm

Basically, there are few key points to keep in mind. CFM is important based on the type of tools you plan on using. Tools which are used for variable time period (like ratchet, nailer, etc.) can run lower CFM while continuous tools (like grinder, sander, etc) require greater CFM. CFM is at the benchmark PSI levels of 40 PSI and 90 PSI are the guide here.

In most cases, oil-lube is favored over oil-less but oil-lube requires more maintenance. Also, belt drive is favored over direct belt drive. As is dual stage (for high pressure use) versus single stage. HP and tank size are seconday considerations to the other specs. For home use, 110V vs 220V becomes an important issue. Also, if the sucker is going located in your attached garage, low DB level is important too to keep peace in the house with the Missus.

Ultimately, you'll need to figure out your requirements and match them to the right blend of specs. I'll most probably go with a high-end Sears Craftsman model because I am comfortable with that brand and they have the combo of specs that suit my needs. I don't think that is a professional choice but I'm not a professional. Hope this helps and please use this info for what's it worth - that would be free! No warranties expressed or implied!!"

Good luck!

CJ

[ November 18, 2002, 06:16 PM: Message edited by: Cobra Jones ]

 

[Streetrodpainter]

I have had many compressors over the years. once HVLP became mandatory, the CFM requirement went up significantly. my SATA uses about 13 cfm at 40 psi. my old compressor, a 60 gallon 5hp couldn't keep up. 40 psi doesn't sound like a lot, but the high volume reallly uses up the air. it's like opening a 1/2" air hose with no restrictions. after about 10 minutes of spraying, I was waiting for more air. I have a 7.5 hp 120 gallon compressor, with another 60gallon storage tank now. it pumps about 24 cfm at 90psi. you won't really need that much for a hobby compressor. but if you plan on painting with HVLP, get at least 5hp and 60 gallon. another factor to look at is the motor speed. if it runs at 3450, it will burn up a pump in a couple years. get one that the motor spins at 1725. it will also have a big 12" or bigger, pulley on the pump. cheers, SRP

 

[Mark Watson]

Get the biggest one you can afford......

 

[rhygin]

I was at Home Depot last night and they have a special on a 5 or 6 hp 22 gallon standup compressor with a pretty extensive accessaory kit included. Impact wrench, ratchet, hose, bunch of fittings and other things are included for $299. Probably not the BEST stuff, but good enough for non-professional (ie. full time) use. Check it out.

 

[Wes Tausend]

I bought a 4 hp Sears oiless a few years ago because the pump unit is so light. I used it for some side jobs of texturing drywall when I first started railroading and didn't work much. I removed the pump unit from the tank and ran it wide open through the 3/32" air nozzle and it maintained about 24# of pressure which is quite satisfactory for fine texture and some light duty sandblasters. The unit must have weighed about 40# as compared to 100# of rotary texture compresser and separate 1 hp motor.

I only did a few extra jobs with it with about maybe 20 hrs of run time when my son and I put it back on the tank and used it for some autobody air tools. I went in the house to visit with a friend that had stopped and later my son came in, made a sandwich and casually mentioned that the compresser was making noise. I rushed out to the garage just as it blew ...one month out of warrantee. The bolt holding the flywheel had worked loose. It wasn't salvagable. I replaced it with a 6+ HP belt drive with a 60 gal tank. I also got a 5 hp Coleman direct drive for portable work but I don't trust it to run unattended since the Sears incident.

[ November 19, 2002, 11:24 AM: Message edited by: Wes ]

 

[thumes]

I started out with a little 30 gallon 5HP craftsman unitl that was really portable and nice, but any tyoe of sander is too mcuh for it. I upgraded to a two stage industrial unit from sears 5HP 60 Gallon(they just slap their name on it, i say buy the same one without the name for a ton cheaper) The nice thing about the larger units is you can put them in the basement and plumb the lines to tha garage without any problems.

It's a ton quieter than the previous one, doesn't tunr on as frequently, and the 220V is really easy to wire with no major cost (they are just 2 120 lines and a ground instead of 1 hot, a positive and ground) The two stage units are by far the best. Check out the specs at sears:
Sears 2 Stage air compressor

 

[Robert Duncan]

The issue with CFM and tank size is related to heat and water in the air stream (as well as compressor life). If you are using so much air that the pump runs all the time it will run hot, heat the air and trap moisture in the air stream. Water is bad for painting and sandblasting, and can be bad for air tools. The heat also kills the compressor.

The idea is to get a setup that only runs once every 15-20 minutes or so. This allows the air (and the pump) to cool. Then the water condenses out of the air and can be trapped by a water separator.

A large tank allows you to draw air for a longer period while the compressor rests and cools. If the tank is so large that the compressor has to run for 15 minutes just to fill it, you are still overheating the compressor. There is a balance between the tank size and compressor output.