Airless Spraying—From Pump to Pattern | Article 2 of 18
How to Read an Airless Spray Tip Number
Three Digits That Control More Than You Think
An airless spray tip is small enough to disappear in a pocket and important enough to control the performance of the entire spray system.
Those three numbers stamped on the tip are not a model number pulled out of a hat. They provide two useful pieces of information: the approximate width of the spray fan and the size of the tip orifice.
Learn to read those numbers and the tip stops being a mysterious little part at the end of the gun. It becomes what it really is—the metering and pattern-forming component of the airless system.
The Tip Number Is a Starting Point
Most commonly used airless spray tips carry a three-digit number such as 311, 515, 517, or 621. The number helps identify the tip’s nominal fan-width designation and orifice size.
For a common three-digit airless tip number:
- The first digit relates to the approximate fan width.
- The last two digits identify the nominal orifice size in thousandths of an inch.
The system is easy to understand once you separate the first digit from the last two.
Example airless tip:
5 × 2 = approximately a 10-inch fan
15 = a 0.015-inch nominal orifice
Reading the First Digit: Approximate Fan Width
With the common three-digit numbering system, multiply the first digit by two to estimate the fan width in inches when the spray gun is held approximately 12 inches from the surface.
| First Digit | Calculation | Approximate Fan Width |
|---|---|---|
| 2 | 2 × 2 | 4 inches |
| 3 | 3 × 2 | 6 inches |
| 4 | 4 × 2 | 8 inches |
| 5 | 5 × 2 | 10 inches |
| 6 | 6 × 2 | 12 inches |
A 515 tip and a 517 tip are therefore designed to produce approximately the same nominal fan width. Their difference is found in the size of the opening.
Remember that the calculated fan width is an approximation, not a guarantee measured with a ruler. The actual pattern can be influenced by:
- Distance between the gun and the surface
- Fluid pressure
- Coating viscosity and temperature
- Tip design and manufacturer
- Tip condition and wear
- Sprayer capacity
- Restrictions elsewhere in the system
Move the gun farther from the surface and the pattern becomes wider. Move it closer and the pattern becomes narrower. That does not mean gun distance should be used as a substitute for selecting the proper fan width.
Reading the Last Two Digits: Orifice Size
The final two digits indicate the nominal tip-orifice size in thousandths of an inch.
For example:
- A 311 tip has a nominal 0.011-inch orifice.
- A 413 tip has a nominal 0.013-inch orifice.
- A 515 tip has a nominal 0.015-inch orifice.
- A 517 tip has a nominal 0.017-inch orifice.
- A 621 tip has a nominal 0.021-inch orifice.
The orifice affects how much coating can pass through the tip at a given pressure. A larger opening can generally deliver more material than a smaller opening under comparable conditions.
That does not mean a larger tip is automatically more productive. If it applies more coating than the surface, operator, or sprayer can manage, the result may be runs, sags, excessive film build, poor control, wasted coating, or a pump that cannot maintain pressure.
Fan Width and Orifice Size Perform Different Jobs
The first digit and the last two digits should not be treated as one inseparable number. They describe two different tip characteristics.
| Tip Number | Approximate Fan | Nominal Orifice | What Changed? |
|---|---|---|---|
| 313 | 6 inches | 0.013 inch | Narrower fan with a smaller orifice |
| 413 | 8 inches | 0.013 inch | Wider fan with the same nominal orifice |
| 513 | 10 inches | 0.013 inch | Still wider fan with the same nominal orifice |
| 515 | 10 inches | 0.015 inch | Same nominal fan with a larger orifice |
| 517 | 10 inches | 0.017 inch | Same nominal fan with a still larger orifice |
This distinction matters when adjusting coverage and material delivery.
If the nominal orifice remains the same while the fan width becomes wider, a similar amount of material is distributed across a broader pattern under comparable conditions. The coating may be spread more thinly with each pass.
If the fan width remains the same while the orifice becomes larger, more material may be delivered through approximately the same pattern width. Film build can increase quickly.
What the Tip Number Does Not Tell You
Reading the number is useful, but it does not answer every selection question.
The number alone does not tell you:
- Whether the tip is appropriate for the coating
- The exact flow rate under every operating condition
- Whether your sprayer can support the tip
- Which filter mesh should be used
- Whether the tip is designed for standard or lower-pressure spraying
- Whether the tip is new, partially worn, or worn out
- Whether the coating has been properly prepared
- Whether the selected fan width fits the surface being sprayed
Manufacturers publish tip-selection charts that provide coating recommendations, flow information, filter guidance, pressure ranges, and sprayer-capacity requirements. Those charts should be consulted along with the coating manufacturer’s product data.
Prefixes, Suffixes, Colors, and Tip Families
Modern airless tips may carry more than three digits. A manufacturer may add letters, product-family names, colors, or other markings to identify the tip design.
Those additional markings may distinguish:
- Standard-pressure tips
- Low-pressure or high-efficiency tips
- Fine-finish tips
- Line-striping tips
- Heavy-coating tips
- Reversible tip designs
- Specialized application families
Colors and letter codes are manufacturer-specific. A color used for one purpose by one manufacturer should not automatically be assumed to mean the same thing on another manufacturer’s product.
The familiar fan-width and orifice code may still appear within the complete designation, but always verify the numbering system with the tip manufacturer.
A Note About Four-Digit Tip Numbers
Some extra-wide tips use four digits. In those cases, the first two digits may identify the fan-width designation, while the final two digits continue to represent the nominal orifice size.
Because numbering formats can vary, use the manufacturer’s chart instead of assuming that every four-digit tip follows the same rule.
The Tip Must Fit the Coating
Thin stains, lacquers, and fine-finish materials may require smaller orifices than heavy architectural or protective coatings. High-solids coatings, elastomerics, block fillers, mastics, and similar materials may require substantially larger fluid passages and more capable equipment.
The coating manufacturer may specify a recommended airless tip range. For example, a product data sheet might recommend an orifice range rather than one exact tip number. The appropriate fan width can then be selected according to the shape and size of the surface.
If the product data sheet recommends a 0.015- to 0.019-inch orifice, several fan widths may be available within that range. A narrow tip may provide better control on a post, rail, or narrow component. A wider tip may improve production on a wall or large panel.
The coating determines the acceptable orifice range. The workpiece helps determine the fan width.
The Tip Must Also Fit the Sprayer
Every airless sprayer has a maximum recommended tip size. That rating represents the largest tip the equipment is designed to support under specified conditions.
A pump that supports a 0.017-inch tip may not maintain proper performance with a 0.021-inch tip. The larger opening demands more material. If the pump cannot keep up, pressure can fall while spraying and the pattern may become incomplete or poorly atomized.
Maximum tip ratings may also change when operating more than one spray gun from the same pump. Two guns do not each get to use the single-gun maximum. Their combined material demand must remain within the capability of the equipment.
The tip sits at the end of the hose, but it determines how hard the entire system must work.
A Few Practical Examples
Example 1: A 311 Tip
A 311 tip indicates an approximate 6-inch fan at the reference distance and a nominal 0.011-inch orifice. It provides a narrower pattern and relatively small opening.
Example 2: A 515 Tip
A 515 tip indicates an approximate 10-inch fan and a nominal 0.015-inch orifice. This is a commonly recognized size, but popularity does not make it correct for every coating or surface.
Example 3: Comparing a 515 and 517
Both tips have the same nominal fan-width designation. The 517 has the larger orifice and can deliver more material under comparable conditions.
Example 4: Comparing a 315 and 515
Both tips have a nominal 0.015-inch orifice. The 315 produces a narrower nominal fan, while the 515 spreads the material across a wider area.
Common Tip-Number Mistakes
- Calling 515 the tip’s pressure rating: The number identifies fan width and orifice size—not operating pressure.
- Reading 515 as a 0.515-inch opening: The nominal opening is 0.015 inch.
- Assuming the first digit is the exact fan width: The first digit is commonly doubled to estimate the nominal width.
- Selecting by fan width alone: The orifice must also suit the coating and sprayer.
- Selecting by orifice alone: The fan must fit the surface and desired control.
- Assuming every manufacturer uses colors and letters identically: Additional markings must be verified with the manufacturer.
- Ignoring tip wear: A worn 515 no longer performs like a new 515.
Before Installing a Tip
- Check the coating manufacturer’s recommended tip-orifice range.
- Select a fan width appropriate for the surface.
- Confirm that the sprayer can support the selected tip.
- Confirm that the filter arrangement is appropriate.
- Make sure the tip and guard are compatible with the spray gun.
- Inspect the tip, guard, seal, and gun for damage or wear.
- Follow the manufacturer’s installation instructions.
- Test the spray pattern before beginning production.
Safety Notice: Relieve Pressure Before Handling the Tip
Airless spray equipment produces fluid pressure capable of penetrating skin and underlying tissue. Never place a hand, finger, glove, or rag in front of the spray tip, and never use your hand to check a suspected leak.
Engage the trigger lock and follow the sprayer manufacturer’s complete pressure-relief procedure before removing, reversing, cleaning, inspecting, or replacing the spray tip or tip guard. Turning off the sprayer does not necessarily release pressure trapped in the gun and hose.
Keep the tip guard and trigger guard installed while spraying. Use only tips, guards, guns, hoses, fittings, and accessories rated for the maximum working pressure of the equipment.
A suspected injection injury is a medical emergency. Seek immediate emergency treatment. Do not treat the injury as an ordinary cut.
This article provides general educational information. Always follow the instructions and warnings supplied with the specific sprayer, spray gun, tip, coating, and solvent being used.
Check Your Understanding
- What approximate fan width does the first digit of a common three-digit tip number represent?
- What is the nominal orifice size of a 517 tip?
- What is the principal difference between a 515 and a 517 tip?
- What is the principal difference between a 315 and a 515 tip?
- Why must the selected tip remain within the sprayer’s rated tip capacity?
If you can explain the difference between fan width and orifice size without looking back at the chart, you have learned the language printed on the tip.
The Bottom Line
The number on an airless tip gives you two important pieces of information. The first part helps identify the approximate fan width. The last two digits identify the nominal orifice size in thousandths of an inch.
That number does not choose the tip for you. You must still consider the coating, surface, desired production rate, finish requirements, filter arrangement, tip design, and capacity of the sprayer.
Three digits can tell you quite a bit—but only when you know how to read them.
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