Something else i found
The amount of paint and how thick it should be is determined by what the specification is from that paint company. The sprayer manufacturer determines spray tip settings, determined by what type of paint is to be sprayed.Thin Coatings
Stains 009-011
Varnish 011-013
Lacquer 011-013
Acrylic Urethanes 011-013
Oil Base Paints 011-013
Enamels 011-015
Thick Coatings
Acrylic/Latex Paints 015-017
Block Fill 017-021
Epoxy 015-019
PVA Primer 015-017
Elastomeric 019-021
These are examples and reflect a range of different materials. Every paint manufacture will have products that are thicker or thinner than there competitors. Always look to the airless pump manufacture and your paint supplier for suggestions.
Ideas and basic considerations when choosing a airless spray tip size.
* The 3 numbers used to describe a tip size, example 517, refers to the fan size and the orifice size. The fan size of a 517 is 10 inches wide, one foot from the surface being sprayed. The first number is always ½ the actual fan width. The last 2 numbers refer to the actual size of the orifice. These numbers represent thousandths of an inch.
Example, 517 is .017 inches. With a constant fan width, a larger orifice size will apply more paint. An example is a 515 has an orifice of .015 inches and a 517 has an orifice of .017 and applies more paint in the same amount of time. Remember the smaller the orifice the less material will be applied.
* Spray tips wear out with use and this will change the fan width and orifice size. The fan will become more round and smaller as the tip wears out.
A 515 could become a 417 after 50 gallons or less of material sprayed. If you need to spray your entire house and your tip is already a little worn, it would be best to buy a new airless spray tip. A worn tip can be used for primer or finish coats that will be back-rolled.
Recommendations
Consider the width of the surface to be sprayed. Deck railings are thin, 4 inches or less so there is no need for a wide fan. A 211 tip applying exterior deck stain will have a fan of 4 inches and give you great control.
Another consideration is the type. 2 types of spray tips exist, these are flat tips and reversible tips.
* Flat tips do a good job and are the cheapest. These are available in many sizes, but require the use of a special tip housing and cannot be reversed to clear a clog. A needle can be used to clear most clogs.
* Reversible tips are the currant standard for professional paint sprayers. When these clog turning the tip 180 degrees and pulling the trigger can easily clear them. The clogging material is forced out by the pressure contained within he gun.
A good combination of spray tips for general use would be a 311 for fine finishing and a 515 for production work.