A friend of mine recently gave me an old DeVilbis cup gun. All cruded up, something he found on a job or whatever. I spent the better part of a day & a half completely stripping the thing down and cleaning it up. Even managed to get it back together without any left over parts!
Now the question is, how much pressure should this gun take for spraying like laquer and laquer sanding sealer? I’ve got a 3hp compressor and a pressure reducing valve & filter. For my first essay with the cleaned up gun I throttled the air down to 20psi and was shooting some 50/50 nitro sanding sealer onto cardboard to check the spray pattern, etc.
Now, I’ve been using for the past few months an el-cheapo turbine HVLP. By comparison, the DeVilbis produced a rather stunningly beautiful misty spray. I switched to a piece of plywood for a test pattern. Even spraying with the plywood vertical I almost had to *try* to produce runs. But – the spray pattern or fan seems extremely narrow. I’m spraying from 6-8″ from the work. In another topic line, a fellow was advised that he was too close with his Binks cup gun. Am I, too, spraying too close to the work?
From Beautiful Skagit Co. Wa.
Dennis
Replies
The old DeVilbis I have sprays unthinned nitro lacquer very well at aobut 35 PSI on the compressor.
I usually keep the gun about 1' or so from the spray surface.
I like to use straight nitro (semi-gloss) for the first two coats, then thin for the finish coats.
Tom -
Thanks for the reply.
This evening I shot some straight nitro sanding sealer onto cherry veneer plywood (bathroom vanity) at 20 PSI at the regulator. I think Jako's comment about line loss is appropriate since I had a hard time getting a very wide pattern. Sure did lay the finish down nicely, though. The finish coat(s) I thinned 25/75 (thinner to laquer) and got a *little* better pattern but I think the gun still has some goobers floating around since the pattern would be inconsistent from time to time.
Even with all the anomolies, it's head an shoulders above what I had been using. Can't wait to paint my old '74 Land Cruiser! (hehehe)
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From Beautiful Skagit Co. Wa.
Dennis
I have a couple of old JGA guns that I use with pre-cat and automotive metallic acrylic enamel with hardner.I have found that I can work well with pre-cat nitro down to 35 lbs but the enamel seems better at 40-45 lbs.This pressure is at the gun ,not on the regulator .You can get a significant drop in the line,depending on length.
-Dup deleted- Sorry.
Edited 4/29/2004 11:29 am ET by mbl
-Dupe deleted, sorry-
Edited 4/29/2004 11:30 am ET by mbl
-Dupe deleted, sorry.-
Edited 4/29/2004 11:30 am ET by mbl
Dear Dennis,
The comment on being too close was for spraying inside of a cabinet, the back specifically. It said to use a small diameter beam of spray and shoot from the distance, avoiding to have the gun inside of the cabinet where possible.
With an HVLP conversion gun, it's OK to spray as close as 6" or even somewhat less, provided the pressure is lowered and the beam adjusted. It's all about what suits the ocassion and also depending on the size, shape, and so forth of the target, and of the material being sprayed.
However, in general, one should not shoot straight in to the surface (at 90 degrees) but hit at some slant angle so that the spray bounces away and not back towards the source.
It's important to explore what's happening and every time some differences have to be adjusted for.
One way to practice adjustments and learn by doing is to shoot water onto cardboard or any other scrap material. Even onto a wall if it's masonry.
Good luck.
-mbl-
Thanks, mbl.
Four times over (grin)
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From Beautiful Skagit Co. Wa.
Dennis
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