Gravity Gun Cup Leaking

[Jason Lester]

I'm getting my feet wet with spraying in preparation for a bunch of small projects for Christmas presents. I have a big 2-stage compressor, so I decided to go with a cheap HVLP conversion gun to start. I got the one from Harbor Freight that seems to have good reviews there and on Amazon. It seems to be working well except I'm getting leaks where the cup screws onto the top of the gun. Should there be any type of sealant or gasket on that connection?

[John TenEyck]

Make sure the mating surfaces are clean. If it still won't seal when tightened by hand then put some Teflon tape on the threads.

And, yes, the purple HF gun that you can often buy on sale for $10 sprays low viscosity materials very well.

John

[Wayne Lomman]

If it leaks, it needs thread sealant at least. Ordinary Teflon thread tape works. Cheers

[Jason Lester]

Thanks, I wasn't sure if it was ok to use sealant or not on those threads. I'll try that tomorrow. I'll be spraying General Finishes waterborne poly mainly.

[John TenEyck]

You will need to thin any of them in order to spray them well through that 1.4 mm N/N. How much depends upon which product you want to use. The best approach is to get yourself a cheap #4 Ford cup and use that to determine how much you need to thin them to get the viscosity down below 40 seconds, preferably around 25.

John

[Jim Becker]

Not to diverge, but... John, would that gun be well suited to spraying water soluble dye? "Enquiring minds want to know..."

[John TenEyck]

Not to diverge, but... John, would that gun be well suited to spraying water soluble dye? "Enquiring minds want to know..."

Yes, the purple HF gun with a 1.4 mm N/N sprays water or alcohol based dyes very well, and Sealcoat shellac, too.

John

[Jim Becker]

Thanks, John...I've been meaning to ask and the OP's thread jogged my memory, especially when you got into the viscosity thing. I need to move to spraying the dye on my tack trunk commissions for better results. We now return you to your regularly scheduled thread...

[Jason Lester]

I was spraying straight denatured alcohol as a test last night and it worked great other than the leak. The pattern and atomization seemed fine.

[Jim Becker]

Jason, I wonder if the threads are buggered? I'd try the tape or maybe a thick o-ring if the cup tightens down far enough to seat against one.

[Dave Cav]

Yes, the purple HF gun with a 1.4 mm N/N sprays water or alcohol based dyes very well, and Sealcoat shellac, too.

John

More thread drift.

I have 3 of the purple HF guns. For the price they are hard to beat. One I dedicated to clear WB finishes, one is only for shellac and the third one is just for odds and ends. Yesterday I was spraying interior acrylic trim paint to color match some switch and outlet plates. The only caution is you really do need to take them all apart for cleaning, including the needle, nozzle and the collar the nozzle screws into, plus the air cap, of course. The needle is carbon steel and will rust if you don't take it out and clean it and then let everything dry. When I reassemble the gun I put a little Vaseline on the needle, all the threads and the plastic gasket between the body and the collar.

And yes three or so wraps of teflon tape should solve your drip problem, and the teflon tape is for all intents and purposes inert and shouldn't react with any of your finishes.