10 PSI tip......hard rule or just a suggestion?

[Eric Thumb]

I have a Harbor Freight HVLP gun, an older one with the regulator underneath, and the 1.4mm tip says "10 PSI Max" on it. I was just wondering if there was a reason for that (lord knows that I have no idea what I am doing) or if that could be overlooked.

I sprayed lacquer onto most of the doors and trim in the house and I think I set it around 40 PSI or so to get it to work better. I recently began spraying shellac and have tried to keep it at 10 PSI and play by the rules but it seems to disperse better at the higher PSI's.

Thanks

[Bill Neely]

Most conversion guns list 10 PSI at the aircap as operating pressure - inlet pressure should be significantly higher because the conversion guns lowers inlet pressure internally. Exceeding the 10 PSI at the aircap just mean you are probably not in compliance with HAPS standards. Not going to blow the gun up. Pressure at attached regulator should probably be ~20-25 PSI with the trigger pulled.

[Eric Thumb]

"With the trigger pulled"-somehow I must have missed that in all of the posts and books that I have read on finishing. I have not even considered looking at the pressure with the trigger pulled. I've just set it and hoped for the best. I never knew that the fan pattern affected the air pressure either. I might just figure out what I am doing one of these days.

My usual method of finishing is to splatter it on and then sand it back to a socially acceptable level.

Thanks for the info Bill! I'm sure that I will have more questions forthcoming that should be completely obvious to the normal person but this is one more step in the right direction.

[Curt Harms]

Most conversion guns list 10 PSI at the aircap as operating pressure - inlet pressure should be significantly higher because the conversion guns lowers inlet pressure internally. Exceeding the 10 PSI at the aircap just mean you are probably not in compliance with HAPS standards. Not going to blow the gun up. Pressure at attached regulator should probably be ~20-25 PSI with the trigger pulled.

Bill is correct and it's a little deceptive for those 'not in the know'. I'd read once that pressure is reduced internally to about 1/3 of the inlet pressure. So 30 psi at the inlet would result in 10 psi at the tip. This applies to conversion guns only of course.