Bought an Air Compressor, now what??

David Agnew

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I've finally purchased an air compressor. It's a Harbor Freight jobbie: http://www.harborfreight.com/21-gal-25-hp-125-psi-cast-iron-vertical-air-compressor-61693.html

I posted this in "Finishing School" because I need some schooling. My main goal is to shoot waterbourne clear finishes. While shooting stain/dye/paint/oil based stuff may happen at some point, that is not my primary purpose for this investment.

So what do I need now? I've read a ton of stuff about regulators, inline filters, not inline filters, dryers, cup guns, siphon guns, tip sizes, etc etc etc.

Could you guys help with advice about the hardware I need now to be "entry-level" successful?

Thanks.
 
Now the other end of this equation. Spray equipment. What is your plan there? That will help you fill in the in-between. From the gun back - regulator, dryer, filter, compressor.

Spray equipment? High pressure or HVLP? Type of finish dictates tip sizes. Unless you plan on spraying houses, a cup will work just peachy.

You have some more decisions to make, my friend. I do not use my compressor for spraying. Good for lots of other things.

I use an Apollo HVLP set-up. That is an air turbine high volume of air with low pressure to move finish material. There are many other brands out there. Very forgiving. Less over spray. Less finish material consumed. High pressure spraying was much more difficult for me to learn. And a lot messier. Got optimal results the first time with the HVLP rig.

There are also HLVP guns to use with air compressors.

HTH.
 
I think Carol meant to say in her last sentence there are HVLP (high volume low pressure) guns available to use with air compressors. ;) The Harbor Freight HVLP guns get pretty good reviews among the hobbyist auto painter guys, particularly their mini gun.

I'm far from an expert when it comes to spraying finishes, but I think at a minimum I'd want a second mini-regulator at the gun and a decent filter/dryer shortly before the gun. I've had reliability issues with the Harbor Freight mini air filters...I instead ended up finding a serious industrial filter on eBay for a killer price.
 
What will you be finishing? Large items, furniture pieces, or smaller items like boxes, shelves, etc.?

On the smaller side, I use an gravity feed HLVP gun intended for 'touch-up.' It has a 5 ounce (150ml) cup. It's pretty much the only gun I use for most jobs. I got mine from Jeff Jewitt at Homestead finishing. I paid a couple hundred bucks for the gun 'kit' several years ago.

Other than shellac, I've been using waterborne finishes pretty much exclusively for the past several years. I use Target Coatings "EM" series of finishes, from sanding sealer up thru their conversion varnishes. By far my favorite, and the easiest, most forgiving one to use is their EM-6000 waterborne lacquer. It's water clear, can be tinted, and goes on very smoothly with at about 10psi at the gun tip.

You'll need some sort of filter/dryer in your air line between the compressor and the gun, and a separate, miniature regulator at the gun itself is quite helpful.

For sanding sealers, etc., I generally use one of the inexpensive guns from Harbor Freight. The actually work quite well. Their 'professional' gun, with a 22 ounce cup, also works very well for finishing bigger pieces.

Hope this helps.
 
Usualy I am 100% in agreement with Jim, but the law says to be HVLP you have to have 5 psi at the tip. However, you may have 10-20 or more psi entering the gun. Boyle's law (I said that to try and impress you) says that if you double the pressure, you get half the volume. Therefore I run the full 90-120 psi on my small air hose, which gives me a lot of air in a small hose, and buy an additional pressure adjuster (about $5) at the gun so the air expands as the pressure is reduced. If I were to reduce the pressure at the compressor I would need one of the fat stiff hoses like I have on my turbine system, to get the required air volume.

I do not use a filter or dryers in the air line. Maybe I should.

I own and have used multiple Harbor Freight cheap guns. They work well for a $25 or $50 gun, but not nearly as well as the better guns. I set a minimum of $100 for a good gun, and although I primarily use a turbine, have several friends who have invested in the CATech Jaguar guns - both complaining about the cost, but both bragging about how much better it is than any other gun they have used.

If I missed something, you should know I have opinions on everything! Ask again
 
Usualy I am 100% in agreement with Jim, but the law says to be HVLP you have to have 5 psi at the tip. However, you may have 10-20 or more psi entering the gun. Boyle's law (I said that to try and impress you) says that if you double the pressure, you get half the volume. Therefore I run the full 90-120 psi on my small air hose, which gives me a lot of air in a small hose, and buy an additional pressure adjuster (about $5) at the gun so the air expands as the pressure is reduced. If I were to reduce the pressure at the compressor I would need one of the fat stiff hoses like I have on my turbine system, to get the required air volume.

I'm likely confused by the wording somehow but isn't that what Jim suggested? Have a regulator at the gun so you can keep the hose pressure high?
 
I think what you guys are saying about having a regulator at the gun makes sense.

So do I need a dryer or not? On the surface of the issue, it seems like having moisture in the air when spraying waterbourne material shouldn't matter.
 
I think what you guys are saying about having a regulator at the gun makes sense.

So do I need a dryer or not? On the surface of the issue, it seems like having moisture in the air when spraying waterbourne material shouldn't matter.

Having a regulator at the gun is relative. I don't like having a regulator attached to the input of a spray gun; it can get in the way when spraying inside a cabinet at times and it's just bulky. My option is having a regulator at the end of the hard line (copper, in my case) with a 12-15' length of 3/8" flexible hose to the gun. It works fine for me. I've sprayed everything from thinned shellac to acrylic outdoor paint with an HVLP gravity-fed conversion gun.

As to brand of gun, I have used HF conversion guns with no problem. I also have a PC conversion gun that is somewhat better and costs three times as much. A turbine system might be the best way to go according to some folks, but commercial shops I've been around gravitate toward SATA conversion guns. My pockets aren't deep enough for that kind of gun, though.

Edit: Forgot to add that I have a drier at the output of the compressor as well as at the end of the copper where my spray line attaches. Both empty automatically when the pressure is released by shutting off at the tank.
 
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I think what you guys are saying about having a regulator at the gun makes sense.

So do I need a dryer or not? On the surface of the issue, it seems like having moisture in the air when spraying waterbourne material shouldn't matter.

Yes you need some kind of dryer filter. Yes it matters the air coming from the compressor is not clean water most of the time it has oil in it .................not good for finish work
 
I'm likely confused by the wording somehow but isn't that what Jim suggested? Have a regulator at the gun so you can keep the hose pressure high?

I run about 90 psi up to the gun, then use a gun-mounted regulator to drop it to 5~10 psi at the tip. I wasn't aware that HVLP was defined as 5 psi max. In any event, the gun functions well, and the EM-6000 goes on very nicely, and isn't that the desired end?
 
I'm likely confused by the wording somehow but isn't that what Jim suggested? Have a regulator at the gun so you can keep the hose pressure high?

Jim suggested a tip pressure of 10 psi. The pressure drops in the gun so to get a tip pressure of 5 psi you may need an inlet pressure of 10 psi or more. One gun I know has an HVLP cap that keeps tip pressure to 5 psi and a second cap if the pressure police are not around that gives slightly better transfer at (implied) 7 psi at the tip.

If you have an oil bathed compressor, you certainly need a filter - oil gets in the air. If you have a cheap (dry) compressor, we can debate the need for a filter.
 
I run about 90 psi up to the gun, then use a gun-mounted regulator to drop it to 5~10 psi at the tip. I wasn't aware that HVLP was defined as 5 psi max. In any event, the gun functions well, and the EM-6000 goes on very nicely, and isn't that the desired end?

What kind of CFM at what PSI are you pushing?
 
What kind of CFM at what PSI are you pushing?

Not sure what you mean. My compressor will do 9cfm @ 90psi, but the HVLP gun is regulated down to about 20psi at the inlet, which puts about 7psi to the tip.

I have no idea what the resultant air volume is, but the compressor (30 gallon tank with 150 psi switch setting, cycles on at 125psi) only cycles about once every 15~20 minutes of spraying. I run a 3/8" hose to the gun.
 
That's basically what I was wondering. Sounds like a bigger 3-5hp machine. My new compressor specs just under 6cfm @ 40psi. I'm seeing a lot of guns that want 6-7-8cfm at 20-40 psi. Maybe I'll be okay w/ a 3/8" leader on the gun. I'm not too worried about cycling, that's what hearing protection is for! :)
 
That's basically what I was wondering. Sounds like a bigger 3-5hp machine. My new compressor specs just under 6cfm @ 40psi. I'm seeing a lot of guns that want 6-7-8cfm at 20-40 psi. Maybe I'll be okay w/ a 3/8" leader on the gun. I'm not too worried about cycling, that's what hearing protection is for! :)

One of the smaller "touch-up' guns oughtta work well. The one from Homestead that I recommended earlier will work well with that compressor. Jeff also has several other guns designed to work with smaller compressors. Look at the website, then give them a call. they'll be glad to help you.
 
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