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Airless spray tip code: fan width and orifice size

a=⌊N100⌋d=N−100×aW=5×aWin=2×ao=d1000omm=0.0254×d
where
a
first digit of the tip code
N
three-digit tip code
d
last two digits of the tip code
W
fan width at 30 cm from the surface (cm)
Win
fan width at 12 in from the surface (in)
o
orifice diameter (in)
omm
orifice diameter (mm)
Explain this equation

Decodes the three-digit number stamped on an airless spray tip, so you can pick the right tip for the paint and the job.

N is the code on the tip. a is its first digit and d its last two. W and Win are the fan width the tip sprays from 30 cm (12 in) away; o and omm are the size of the hole the paint passes through.

Graco and most makers use the first digit as half the fan width in inches (or a fifth of it in centimetres) and the last two digits as the orifice in thousandths of an inch. The floor brackets just pick off the first digit; 0.0254 converts thousandths of an inch to millimetres.

Sense check: a 517 gives a 25 cm (10 in) fan through a 0.017 in (0.43 mm) hole, a common choice for emulsion on walls. A 621 gives a 30 cm fan through 0.021 in, for thicker paint or bigger areas.

Watch out: worn tips pass more paint with a narrower fan, so replace them before film build and consumption creep up.

Decodes the three-digit number on an airless spray tip into the fan width and orifice size.

code

Enter your values to see the result.

Good to know

Graco's system: the first digit times 5 gives the fan width in centimetres (times 2 in inches) when spraying 30 cm (12 in) from the surface; the last two digits are the orifice diameter in thousandths of an inch. A 517 tip gives a 25 cm (10 in) fan through a 0.017 in orifice. Flow rises with orifice size, so a bigger orifice suits thicker paint or a bigger pump; a wider fan covers faster but puts the same flow over more area, giving a thinner film per pass. Check the paint data sheet and the sprayer's maximum tip size.

Common mistake

Carrying on with a worn tip. As the orifice wears it passes more paint while the fan narrows, so film build rises, edges get heavy and consumption climbs.

Limits

Nominal figures for a new tip at its rated pressure. The actual fan varies with pressure, paint viscosity and wear. Other makers use similar codes but check their charts. Reversible tips with a leading digit (for example 6 in some fine-finish ranges) may follow different conventions.

Sources

Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.

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