Apprentice Member
Posts: 4
Registered: ‎04-01-2010

HVLP Sprayer - how to determine Nozzle/Needle & Air Cap size

I am a woodworker and want to spray varnish and poly (oil & water), stains and lacquer. I would also like to spray acrylic latex paint, and oil based enamel paint on inside trim and cabinets.


I have acquired an Accuspray 230 HVLP system with the series 10 bottom feed gun (non bleeder).


I have Needle/Nozzle sizes 0.9, 1.1, 1.3 and Aluminum Air Caps 6,7,8,9 & Delrin Air Cap 10.

I have seen numerous charts for the Accuspray on the internet that show all kinds of combinations of N/N sizes with various Air Caps sizes for the same N/N.  Small N/N with big AC, big N/N with small AC.

Then there is the fan pattern, and fluid amount and the "to thin or not to thin" product verses increasing the N/N.
Then the viscosity cup - some use #4 Ford, other #2 Zahn. And where do you find the flow spec of a product anyway?
Where does one start? With the N/N size for the product being used? Why would you use an air cap different from the one "normally" sold as a set?
Thanks for any guidance.
Honored Advisor
Posts: 3,468
Registered: ‎10-26-2009

Re: HVLP Sprayer - how to determine Nozzle/Needle & Air Cap size

[ Edited ]

I would seriously reconsider the deisre to spray oil-based poly and oil-based paint.    These just dry very slowly.   The atomized droplets will float around, land on something, then cure.   Compared with faster drying products such as acrylic, lacquer, and shellac where the atomized droplets float around, dry, then land as dust on surfaces.  


In addition, reactive finishes do not dissolve in their solvents as do evaporative finishes.   So if you do not keep your gun very clean, you will find a big problem with product build-up inside it and gum up the parts.   If you do this with lacquer, for example, all you do is soak & brush in lacquer thinner and you have a clean gun.  In addition, if you use one product one day and a different product another day, there's a chance of interaction of bits inside the gun.  For example, you start to spray clear lacquer and you start spitting chunks of yesterday's latex white paint that the lacquer solvents have softened and loosened from inside your not-so-clean gun.



Latex paints are very thick and most guns will have a hard time getting them to flow and atomize.   Painters who use these use airless or airless/air assisted guns.   If you want this, get a sprayable acrylic finish and have the paint store tint it.


As far as cup timings, etc., your finish product data sheets and technical material on your gun should provide some information for your guidance.  A tech rep from a gun company once taught me that with the airflow through the cap off, your fluid should squirt out about a foot.