Air Compressor Buying Basics?

[rebocardo]

>  to use an air grinder from

When using an air grinder or cut off tool, you really need a lot of CFM. A someone mentioned, at least 22 CFM @ 90 PSI. That = $$$$

For light normal use, get something that puts out 6 CFM @ 90 PSI (not 40!). This would be about $300 from northerntools.com. This is enough to run most air tools for a few minutes including an impact wrench.

The nice thing about a small 120v 6CFM@90 compressor is it is light enough to put in your truck and take somewhere. Same deal with a a 120v MIG welder.

[isawlogs]

I also have (  Campbell Hausfeld 5HP, belt driven, oil lubricated, cast iron cylinders on a 20 gallon tank with wheels (whew!  ) runs on 110V  ) I can also wire the motor to run on 220  
  Thanks Charlie it was faster to copie and past , hope I didn't infringe on any copiewrite laws here ....  ;)
  If I had to buy another it would be a little bigger and standing,

[Larry]

Few more comments on air compressors.

I plumbed my shop with PVC the first time.  Pipe is plenty strong but fittings are rated a lot less.  I had trouble with them cracking and then leaking.  Running 175 psi from the big compressor.  Second thing if you have a little fire and it melts the PVC you will have an inferno in seconds and your insurance company may not cover the loss.  Running copper in the new shop.

The big compressor is an Ingersol Rand 7-1/2 hp with 80 gallon tank.  It may be the Cadillac of compressors but when it comes on you can hear it a mile away.  If in the shop you need ear muffs.  Wish I had the Quincy that Quartlow was talking about.  

I have never seen a compressor over a true 1-1/2 hp that could run on a standard 110V 15 or 20 amp circuit.

My little DeVilbiss oil less compressor really does not make very much noise.  Not promoting any brand but it is pretty quiet.  Nothing like some of the other models.

[Gilman]

Larry has a good point about the pvc, with its low melting point and potential to crack.

Here are some features that have worked out well for me.

The first is a paticle/water collector that is at the bottom off all the drops.  The main lines are in the attic coming from the compressor.


Here's the air compersor mounted on a mezanine. No point in wasting valuable floor space.  It's a 7 1/2 hp 2 stage compressor that came out of a navy ship.


Here's some of the air tools put away on a mount.  Most of the tools are held in place by their air fittings. The large tools like the impact wrenches slide into a large hole that is a little bigger than the tool body.


Here's a closeup of the compressor mounted to the plumbing system with a flexible hydraulic hose.


The is the best feature in the air system, an outdoor fitting.

[DanG]

Oh, you people make me sick with you fancy shops, and all! :D :D  You oughta see mine! :

Larry, I agree and disagree. You said, "true" 1 1/2hp, which is a figment in today's world. HP is strictly a sales tool any more, imho. I have a 1400lb horse that can go from 0-40 in about 3 seconds with my 200lb butt on her. Show me another 1hp motor that can do that!  It seems that HP ratings are just assigned by marketing groups to get max sales. My 16hp mower don't cut a bit faster than the 10hp model it replaced. ???

On the other hand, 120v @ 20a should produce about 3.2 mhp.(Marketing HorsePower). ;D

[iain]

what ever you get make sure the air going in is CLEAN  
i got a 7.5hp 80gal ingersol 1987 came from jims paint shop when he retired
 im also surrounded by workshops with compressors (six) there all loud cept the air screw one in the top yard that runs 75cfm its really quiet

[Paschale]

OK...I've finally had some time to process all this information!   :P

Thanks for all the info, guys--once again, the brain trust of the forum comes through.   8)

So, I've gleaned a few ideas from the thread, but it's raised a few more questions too.

Seems like a minimum is a 5HP, 20 gallon compressor.  Ideally with a cast iron cylinder, and ideally a 2-stage.  And I'm wondering if the two stage is a two cylinder compressor?  

For me, anything around $1000 is way too expensive right now.  But what confuses me is that Gilman says that for paint spraying, you need a large tank, though sounds like j_goodhart does this with a 20 gallon tank.  I'm thinking that a "large" tank is more into the 60-80 gallon tank.  Can you do painting with a 20 gallon tank OK then?  sounds like Buzz, that you're able to do some painting OK with that cambell-hausfeld.  Can you get a nice paint job with one of these?  I'm a little confused.  

It sounds like I should sorta give the idea of sandblasting the heave-ho.  Sounds like a dirty, messy, thankless job, and that in order to really do it well, you should use a big ole tank.  Though jgoodhart says he's able to do it with a smaller tank--he just gets "built in" breaks from time to time, which are greatly appreciated.    ;)  From what you all said, though, I'm thinking using a grinder is the better way to go.

Speaking of air grinders...I'm a little confused on this one too.  From what everyone said, it's surprising how much air an air grinder uses.  I guess I'm wondering if I go with a "Campbell Hausfeld 5HP, belt driven, oil lubricated, cast iron cylinders on a 20 gallon tank with wheels (whew! :D )," will I be able to successfully use an air grinder?  And do some painting?

The most important thing I learned:





DON'T BUY OILESS!!!





 :D

Thanks for all the help guys!   8)

[J_T]

I once quick hooked a hundred lb lp tank to a small compresor and ran a tire machine 8) I now have one them cambelhasfeild jobs an use a binks #7 paint gun most painting is at a low presure and you need to stop and fill ever now and then.  Mine was cheep and on sale it had a bunch of tools plus a good warrenty at walley world ;D

[etat]

Unless ya got lots and lots and lots of air, just go ahead and get an electric grinder.  For small jobs them smaller electric grinders are hard to beat.  An air grinder, or buffer even  suck the air outa a little outfit quick, and ya'll be taking more breaks than ya want to. And getting aggravated at the same time.

You can absolutely paint with a smaller compressor, but you can't do as good a job on something like a car or truck where once you get started you need to keep moving.  It CAN be done but it's harder to get as smooth a finish. For fine finisheses a bigger compressor, and HVLP paint gun is the ticket.

A two stage can be one cylinder.  It pumps both on the up, and the down stroke, I 'believe' I'm right.

I'd REALLY like to have me that ole 4 cylinder unit.

Sandblasting, along with painting a base coat, clear coat type automotive  paint is among   the most horrible jobs in the world. I personally will NEVER again paint base coat, clear coat.  Proper respiratory gear is an absolute necessity. If you want to keep breathing that is.  

A air paint gun does not paint latex or heavy equiptment type paints very well, if at all.. Especially a smaller outfit. For these type paints, especially latex,  a commercial, airless, electric paint sprayer is the best option.

I would not buy a larger type tank with wheels.  I'd get a longer hose.  If I wanted portable, and I use one EVERY single day to run nail guns, I'd go with a smaller oiless compressor.  Get something larger than the small pancake type compressor though.

One thing that may be of intrest.  Most semi portable belt driven, oil filled compressor, WILL NOT keep my nail guns running.  Some contractors use em, and many have invited me to plug into their compressor.  The bigger tanks on em will hold more air of course, but all I've run across pump down too low before kicking back on.  And then wait too long to pick back up enough pressure to keep the nails fully driven. A 'good' oiless compressor will kick back on when the pressure drops to 90 lbs, and take only a few seconds to pump back up. And all the time we're shooting them guns wide open. As I said with the belt driven we have to wait a minute for the pressure to come back up. More often than not I'll have them contractors just go ahead and hook their guns up to my 'little' compressor. They ain't ever shooting their frame guns as fast as we are nailing on shingles anyways.

My choices would be 'either, or'.

Shop type, 80 gallon tank two stage, stationary.

If I couldn't have that I'd go with a oiless portable, name brand, with an oil splash on the cylinder  that'd pump as much air as possible with a 110 motor.

I wouldn't get anything in between.

My recomendation for semi oiless, and I've used about ever type there is.  

http://woodworker.com/cgi-bin/FULLPRES.exe?PARTNUM=114-080&LARGEVIEW=ON


This is NOT a loud compressor.

I've got more commercial time on this compressor in the past year and a half than most average homeowners would get in ten years.

Either way the CFM, and recovery time compared to what tools you'll be using is what you want to go by when making your decision.

Some will lie about their horse power, cfm, and recover time.  

Sorry fer confusing you even more.

[J_T]

Ck get on that presure switch with your screwdriver  :D :D Once I set the off pressure with the relive valve you can set the on at what ever you want to. I know where thare is a screw compressor beleive it was used at a cly Co . One them things I hid a while back.

[Quartlow]

I'm firm believer in single stage for most use's.

A 2 stage compessor use's 2 cylanders or incraments of 2 cylanders. Cylander one is larger in diameter than cylander 2 in most cases. Air is sucked into 1, on the compression stroke it forces the air into cylander 2 which pumps it into the tank. The advantage of a 2 stage is higher operating pressure's. Since you are forcing the air into 2 you are creating basickly a supercharged compressor.

Most air tools operate in the 90 to 120 PSI range. While higher pressures  will make a 1/2 inch impact do more you shorten the life of the impact gun this way.

2 stage compressors generate more heat which also equates into shorter compressor life and more water in the system.

Now on the average most single stage compressors will generate more volume but at lower pressures. The one thing to keep in mind here is they sell them buy the HP range of the motor not the compressor. To truly compare a compressor you need to know the cubic inches of the compressor and the amount of air genorated of CFM ( cubic feet per minute)

I've seen 7 HP 2 stage compressors that only produce 13 CFM at 90 PSI and 5 hp single stages that produce 12 cfm at 90 PSI

Most single stage compressors shut off at 125 to 135 PSI So why would you need a 2 stage that goes to 175 PSI?

You not going to paint at 175 PSI or run a nail gun at the pressure. So why waste electric making pressure you don't need.

We have 3 compressors here on the farm a 7.5 HP single stage a 5 hp single stage and a 3 hp single. The 3 and the 7 are both Ingersoll rands. Both are over 10 years old. The 5 horse is an off brand chinese thing. Its 2 yearts old and its whipped allready.

IMHO you want a single stage that makes the greates amount of CFM for a given HP range

[VK540_1]

I just purchased an air compressor and now I would like to buy a nail gun to use with it. I would like a gun that would be good for nailing osb on floors walls and roofs. Is a brad nailer good for this or would I need a framing nail gun? Any brand recomendations ?

[jgoodhart]

Check out this site got some big compressors cheap if you have a power sorce or tractor to run them.  I dont know if the link works but www.hgrinc.com will get you there than search inventory. http://www.hgrindustrialsurplus.com/List.asp

[jgoodhart]

Wow the link works, just went to the wrong section :-/. 1st time I did that.

[Gilman]

Wow, great prices on the dust collectors.