harbor Freight HVLP Question
Ok so I have one of the HF knock off hvlp guns and wonder if my compressor is big enough to run the gun. My compressor is a CH 20gal 5hp 125psi with reed valve pump.
When spraying primer the material delivery was far less than adequate. What would have taken me 15 minutes with a siphon gun took nearly an hour because I had to go so slow over the surface. The compressor only kicked on occasionally so I think I have enough pressure but what about the CFM? The gun asks for 9.5 cfm and I think my compressor puts out 6.5.
Any help would be greatly appreciated.
Ben in SC
You will probably have enough air pressure and CFM to do a small amount of spraying but with a 20 gal. tank you'll probably see a drop in pressure after spraying a panel or two. Spraying an entire car is probably out of the question.
Keep an eye on the pressure as you spray, if you see it start to drop you'll need to stop and wait for the compressor to catch up. When you need to stop spraying during the application of your top coats you can generate dull areas because the paint on the surface tends to dry at the point where you stopped the application. A larger tank would allow you to go further before your pressure drops. If you try to keep spraying at a reduced pressure you will generate even more texture problems especially using an HVLP gun.
Last edited by Len; 12-04-2005 at 10:16 AM.
CFM has to do with the out flow of the compressor. If it's not running and you're having a problem with your painting, the problem is not with the compressor volume. Inadequate hose size could restrict the cfm flow to the gun, but obviously since the comp is not running it's not a matter of the compressor not keeping up with the gun, and I doubt very much it's air volume at all that is your problem.
I suspect that your problem is the tip size on the gun when spraying heavier materials. I bought a cheap Porter Cable gun that came with a 1.5 tip. I used it for everything, base, clear, epoxy and high build 2 k primers. Works okay, maybe even well, with the base, clear and even the epoxy when thinned, but woefully inadequate when shooting heavier primer. Recently purchased a 2.0 tip because I wanted to shoot polyexter fillers and dedicate this as my primer gun, and what a difference. I am now moving my gun at the same speed I would with the lighter materials in the 1.5 tip.
Thanks for the reply Len.
The compressor actually only ran periodically during the spraying of the bottom of the car. The problem I was having is with the primer application.
Maybe I dont have the gun setup right? With the primer atomized there just isnt enough coming out of the gun to paint at any speed. With more flow the paint droplets are to big and it almost spatters.
I think Steve has the answer. If the tip is too small for the viscosity of the material being sprayed you won't get enough flow from the gun to do the job properly.
Another factor is that inexpensive guns are usually not engineered or machined as well as better guns and the same tip size on a better gun could produce an entirely different result. This would probably be due to the fact that (on a better gun) you would PULL more of the material out of the gun with the flow of air from the air cap.
The tip is a 1.4 on this gun. One other thing I notised was that the flow would look good for a few second then it would die off. I have 25' of 1/2" line on the compressor.
I am tempted to go out and get a bigger compressor today but would hate for that to not solve the problem. I am spraying MP182 right now. Maybe it started setting up int he cub and got to thick?
Something to check...
If the air intake to the cup is clogged you may be stopping the flow of material to the tip. Check the hole in the cup's cap to make sure it is open. This is usually the problem if the gun starts out ok then the material flow becomes less and less.
I had the same problem.
I knew my 80 gallon 2 stage compressor was not it.
I tried reducing (thinning out) the filler and that didn't really help.
(it still spit not sprayed)
Len is right...........
First - Make sure paint that the hole in the paint cap cup is open.
Second - Break down and buy a gun with at least a 1.7 tip for shooting 2K style primers.
What a difference.....
The stuff just flows on,fills small imperfections and dries as flat a pancake
Great! Now I need to see if I can order a larger tip for this gun... Are the nozzles made specifically for individual guns? What would be a good source for an inexpensive nozzle for this cheap gun?
Thanks for the ideas!
Last edited by BenWillis; 12-04-2005 at 06:29 PM.
I'm pretty sure you can get several different tip/air cap sizes for your gun right from Harbor Freight. Go for a tip between 1.9 - 2.1 size for shooting 2-K primers. Better yet just go buy a cheap siphon feed conventional asian knockoff gun (non hvlp) for around $20 - $25 and use it for 2-K primer only.
If you were near me here in Michigan I'd give you an old gun for nothing that would do a good job with 2-K primer. A 1.4 tip is just too small for shooting primer that thick. Keep in mind that everytime you shoot 2-K or epoxy primer with that HF gun you are going to have to totally disassemble that gun (or any gravity feed HVLP gun) clean all the parts individually with lacquer thinner then reassemble the gun. Sloshing thinner around in the cup and shooting thinner for a couple seconds don't get it with those type of guns. They will plug up quickly if you don't totally clean all the part that come in contact with primer.
What brand and type of paint do you plan on using to spray your car ?(assuming you are working on a car/truck). That HF gravity feed HVLP gun is not a good choice of guns for spraying BC/CC, you will be disappointed with the results if you use that gun to spray BC/CC.
This is actually my second paint job on a car. I painted a Porsche 911 four years ago and used a siphon gun from Lowes. It was a bc/cc job using PPC Concept.
On this car (1960 Austin Healey Sprite) I'm going with PPG again but a single stage. I just dont think that bc/cc looks good on the old cars that orginally had laquer.
I'll give HF a call tomorrow to ask about the nozzles.
Ben in SC
Last edited by BenWillis; 12-04-2005 at 07:49 PM.
Let me know if HF makes a larger tip. I think I have the same gun as you, that I use for a primer gun.
I have the same gun. Epoxy primer seems to flow slowly for me also. I did work better when I turned the air up 35 to 40 psi. I have a 60 gal 7.5 HP, so I don't think it's the compressor. I called HF, no other tips available. I called then the paint manufacturer, the tech told me to thin up to 4:1:3 tech sheet said 4:1:1/2. He said a mix of 4:1:1 would probably do it. Will thinning the 2K primer be counter productive? Sounds like I need to buy another gun to do my paint anyway.
Im sure you did this but let me remind you. Those guns come with the tip and aircap not tight. This will cause the intermittant spraying. Make sure they both are tight and try again.