[Swede]

I hope this is on-topic enough for the CNC Zone. My shop compressed air system needs an upgrade. I am moving into a bigger shop (yay :cheers: ) in a few months, and need to upgrade my compressor. Right now I am using a tiny little job that's really nothing more than a roofer's portable. I'd rather save my money for CNC stuff, so I am trying to do this cheap.

My demands are no more elaborate than mist coolant, simple air tools, etc. I'd like a vertical job to save on floor space.

Anyone have any experience with Harbor Freight's compressors? What is the advantage of a two-stage system?

Finally, would it be practical to add, say, a 15 to 20 gallon air storage tank (just the tank, no motor) onto my pancake compressor to add capacity? Would this help, or would the compressor cycle just as often as it does now, which is TOO often?

Thanks for any insights...

Swede

[nervis1]

I got a new AC a year ago from Home Depot, a Husky brand (made by CH) 7.5 hp (yea right more like 4, maybe less?) 60 gal. Feeds all my tools, blast cab, and VMC just fine. It was just under 1k from what I remember. 15 cfm @ 90 psi, takes up about two sq. feet of floor space, uses a 1 ph 220 30 amp breaker.

It's a two stage, with oil lube. It's been very reliable even in 100 + degree heat in the summer and 40 in the winter.


http://www.practicalmachinist.com/ub...c;f=8;t=000039


Heres all you need to know thanks to Forrest Addy.

[Ken_Shea]

Dave you beat me to an exact recommendation, they have excellent prices and very respectable units. Swede with what you mention I doubt that you would need the extra storage, but it will not hurt, compressor will kick in less oftem but also for a longer period of time, personally I would prefer it kick in more often and then shut up quicker

[Swede]

That is a GREAT link, thanks guys! Off to Home Despot tomorrow. My poor circuit breaker panel cannot handle too much more.

P.S. the final "straw" was my new Trico Micro-drop system. From what I have seen so far it's really nice. No fog!!

[ViperTX]

Yeah either the 7.5 at $1k or the 5.? at $429 at Home Depot or Lowes....both seem well built one is a 2 stage and the other is a single stage 15 CFM versus 11 or so CFM and both are vertical units...so a 2 stage is generally a 2 cylinder and a single stage is a single cylinder pump.....save the portable for field use....*chuckle*

[Ken_Shea]

Yes Swede, if you can bite the bullet definitely get the greater CFM 2 stage, normally these have higher pressure and will pump up quicker, a big plus, I hate that noise

[kenlambert]

I went with one of the oiless type compressors with the 60 gal tank and 220 volt 6 HP motor it is going on Ten years old now .I used to have an auto repair shop so it has had a lot of usage and still pumps up quik and maintains 95# of pressure running my blast cabinate I gave 350.00 at sears

[Swede]

Did a bit of online search for both Lowes and Home Depot (Sorry non U.S. Zone guys - I always feel weird discussing U.S. merchants like Home Depot on an international forum). There is an obvious and big jump in price and capability going from 1 to 2 stage AC. I probably cannot justify the 2-stage jobs. This particular model looks good - nice, medium range AC for the home, not too small, not too big.

http://www.homedepot.com/prel80/HDUS...4+3966&pos=n24

It is one stage, 2 cylinder, oil lube, 60 gallon, 10.3 CFM @ 90. Changeable air filter. $429.

My new shop will be in a hangar, and looking into the future, and the types of activities I may be into, I can really see needing more compressor than this one. Darn it, this is probably one of those decisions that I may look back on and regret, not getting the better 2-stage unit.

I'll check out Lowes and Home Depot today and will report back. Thanks for the advice. One last question - Lowes features Campbell-Hausfeld compressors. They range from tiny jobs to bigger, 2-stage units. Any thoughts on Campbell-Hausfeld? :wee: (Leaning towards 2-stage... talking myself into it!!)

[ViperTX]

Swede...you could always purchase another unit and place it in a different part of the hangar. Also, I believe that when they say twin cylinder it is really a dual piston in one cylinder. The real 2 cyclinder units are V-twins.

[InventIt]

Dual and single stage compressors:

Single stage can be one or more pistons. The pump (compressor) intakes ambient air and compresses it in one stroke. The compressed air is then pushed into the holding tank.

Two Stage compressors: Have two or more pistons. One piston is large in dia and one is small in dia. The large piston intakes ambient air compresses it to about 90 PSI and exhausts that compressed air into the chamber of the smaller piston. The smaller piston compresses the air further to its final PSI and then into the holding tank. Usually there is a cooler in-between the stages to extract heat.

The advantage to two stage is higher PSI with lower HP req. and usually higher CFM ratings. When comparing units pay attention to PSI rating as well as CFM. CFM will drop off dramatically as PSI increases. So a unit rated 10 CFM at 120 PSI is much smaller then a unit rated 10 CFM at 175 PSI. Also, most of the better units run the pump at a slower speed, 900 – 1200 rpm, this means more air pumping and less wear with less heat buildup.

An air compressor is a life long investment. A good one will last a LONG time. Good units are usually serviceable as well. Get one that will fill your requirements into the future.

Anyway, all this is probably moot if your requirements are light duty or short term.

Whatever your decision, be sure to install a valve at the bottom of the tank to drain condensate.

[InventIt]

One more note, from what I have heard, USA made motors have 2x the power of their China made counterparts. A China brand 5hp is actually only 2.5 hp or less. I forget the reasoning for this but I think it had something to do with rating standards.

I have a Emco compressor with a 3hp GE TEFC motor that performs much better then my dads CH 5hp made overseas job.

[ViperTX]

Well take 746 watts for 1 HP and look at what the motor uses and you'll have the HP.....developed versus actual HP.

[Bubba]

Swede,
I add my 0.015 worth. IF you are ever looking at any sustained use of air tools or especially painting, be sure to look at the useage of the tools them selves (this can very greatly between makes and models) and size your system to their needs. I used to paint cars and bikes on the side with a small compressor (my gun uses 9cfm at 45 to 50 psi) and there is nothing more frustrating than to get to a particular point that is not a good breaking point and run out of air. Same thing goes for your other air tools also.
As pointed out earlier, an air compressor is a lifetime investment. I just replaced one last year that I bought used back about 1977 or 78 and it finally gave up. Actually the motor gave up and it gave me a good excuse to replace the horizontal 60 gal receiver with a verticle 80 AND get a more efficient compressor at the same time!
I just happen to get the one at Lowes as my local Home Depot didn't have any in stock.
Regarding your request on Campbell Hausfeld, be aware this along with many other brands are private labled. To get an idea, look at the site:
http://www.aircompressorsettlement.com/
Which is involved with some of the bogus power listings on air copressors. Yes, sombody is actually doing something about the power ratings on air compressors:})

Bubba

[Swede]

Well, I scored an air compressor at Lowe's, thanks everyone for excellent advice. I tried to imagine my future needs, and the tools that this compressor would power, and ended up compromising towards the middle of the range of compressors. I read the excellent guide linked by Nervis1, and concluded that an oil-lubricated, cast-iron compressor, either 1 or 2 stage, would be fine for my needs. Here's the compressor I bought -

http://www.lowes.com/lkn?action=prod...99-1126-VT6329

It'll do 10 CFM at 90 PSI.

I've noticed that this particular model, like many Chinese mills, is sold under a number of different labels. This is a Campbell-Hausfeld. The EXACT same AC is sold by Home Depot as a "Husky", at the same price too.

All the necessary plumbing (filter, regulator, fittings, etc) was picked up too. I'll wire it up and give it a whirl tomorrow.

[Bubba]

Swede,
That looks like a good unit and should give you years of service. Just as a reminder, if it doesn't have a drain valve on the bottom, be sure to put one. I used a street ell, a nipple and ball valve to get to off center of the bottom of the tank so I could drain it without standing on my head:})

I also bolted it to the floor! That sucker will not move on me!

Bubba

[DareBee]

If for some reason you need more CFM you can always plumb your "Roofer" compressor into the air system as well and run them both. I would make sure to put a 1-way check valve at the tank outlet of each unit to stop back-feeding if you decide to do this.

[ESjaavik]

Wow! A hangar! Just remember workshop space is just like a hard disk: someday it will be too small no matter what size.

Try to get a big tank, or connect several smaller. I have used 50 litre tanks from scrapped trucks. Most non-professional users may draw a lot of air for a short time, but not in the long run. A big tank works like an accumulator. you can use a long time to charge it, but it can return it in a shorter time. It also will let the moisture settle and give less of it in the lines.

If the capacity of the compressor is high, there should be valves that make sure it does notstart against the backpressure of the tank. If even larger, use a soft-starter. Not to be confused with a VFD, it is much cheaper, and only softens the start. These precautions avoids unnecessary tripping of the circuit breakers. (OK, I converted 10cfm to litres/min, and you should be OK with yours if you have some amps. If you will do sandblasting, get some big tanks. I have one a bit bigger, and it's not keeping up when sandblasting.)

Make sure your plumbing is not leaking. That's a waste of money.
Use a main switch in your shop, and connect the compressor contactor to it. Thus if a line or hose burst when you're away, the compressor will not burn.

Don't skimp on pressure tests because you're an amateur. Your life is as much worth as a professional's.

[MetalCNCing]

You can even build a compressor using a car's A/C compressor; you get a lot of air and pressure up to 250PSI, Fill's 20 GAL in about 45 sec. Because of all the tiny little pistons it has (about 12) you get faster air and more pressure!! All you need is a motor about 5-10HP.

[ViperTX]

You can even build a compressor using a car's A/C compressor; you get a lot of air and pressure up to 250PSI, Fill's 20 GAL in about 45 sec. Because of all the tiny little pistons it has (about 12) you get faster air and more pressure!! All you need is a motor about 5-10HP.

Well, I guess I might as well weigh in with this bit of trivia.

Actually the air compressor from a truck that has air brakes is perfect for making a home made air compressor....you can usually buy those little air pumps for less then $45....I think you can even buy rebuilt units for under $100....add an electric motor and a tank....walla...air compressor. What I don't know is "did air brakes precede air compressors or vice versa??"

[Holmes_ca]

Im sorry if I am intruding, but everytime I try to post a new thread in this section I get some kind of error, so my question is I need help in deciding what size compressor I will need for a (mist spray unit I have purchased) cost $15.00us so it is very sparse, just a block of aluminium with a screw valve on top and a unilock? (not sure of name description) outer hose with a small dia of plastic hose inside that leads back to a plasticc bottle,

I have a small compressor a Delta Shopmaster Model CP200-1, with a 2 gallon tank, a cheapy it came with a stapler/nailer, even before the mister starts working the pressure in tank drops to 20/30 lbs and it quits misting,

Can any member calculate the minimum size of compressor that will give me at least intermitant misting so that I know what size to start looking at, I just don't want to buy a 20 hp 60 gallon when a 3/5 hp 10/15/20 gallon will be sufficiant,

I am just a hobbiest machining small components,

Thanking you in advance for any help recieved,

................Edmund..................