Parts of a Spray Gun – Air Cap, Fluid Tip, Needle, Cup

All 12 parts on the diagram

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The gun from the side 9

Trigger Pulling it lets the air through and the paint out.
Cup It holds the paint.
Gun body Air and paint both pass through on the way to the front.
Air cap Compressed air leaves through it and breaks the paint into a spray.
Cup lid It closes the cup and joins it to the gun.
Air inlet The air hose from the compressor is joined on here.
Fluid control knob It sets how much paint comes out.
Pattern control knob It changes the spray from a round pattern to a flat fan.
Packing nut Presses the packing round the needle. This stops paint leaking out along it.

Pulled apart 3

Fluid tip The paint comes out of it. It screws into the front of the gun body, inside the air cap.
Fluid needle With the fluid tip it makes the valve for the paint.
Air valve It shuts off the air when the trigger is let go.

How this list was compiled: Every name checked on 2026-09-30 and kept only where at least two independent sources use it. (1) A maker's manuals for two air spray guns, https://archive.org/details/manualzilla-id-7037160 and https://archive.org/details/manualzilla-id-7037431 , counted as one source: air cap, fluid tip and nozzle, fluid needle, packing nut, trigger, air valve, pattern control knob (open for a flat pattern, closed for a round one), fluid control knob, air inlet, cup, lid, gun body. (2) A second maker's spray gun manual, https://archive.org/details/sears-craftsman-spray-gun-919.156241-manual : air cap, fluid tip, fluid needle and its adjusting screw, packing nut, the built-in air valve that shuts off the air when the trigger is released, air inlet, cup and cup lid, gun body. (3) A third maker's service manual, https://archive.org/details/manualzilla-id-6027295 : fluid nozzle and fluid tip, fluid needle and its packing, air valve, fluid control screw, side port control, trigger, cup. (4) A fourth maker's owner's manual, https://archive.org/details/manualzilla-id-5928164 : air caps, fluid needle, fan adjustment knob, air inlet, trigger, cup and lid. (5) Wikipedia, Spray painting, https://en.wikipedia.org/wiki/Spray_painting : the air gun's nozzle and trigger, and the air nozzle, sometimes called air cap. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's gun, nothing traced. Licence: own work

How it works

A paint spray gun with its cup, seen from the side. The second drawing pulls the front end apart along its axis and cuts the handle open to show the air valve.

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Air and paint

Compressed air comes in at the air inlet under the handle. When the trigger is pulled, the air valve opens and the air goes on to the air cap. Paint comes from the cup to the fluid tip, and the air from the cap breaks it into a spray.

The two knobs

The fluid control knob sets how much paint comes out. The pattern control knob changes the spray from a round pattern to a flat fan.

Makers name the knobs differently. Typed answers take fan adjustment knob for the pattern control knob and fluid adjusting screw for the fluid control knob.

Questions and answers

What are the parts of a paint spray gun?

A gun body with an air cap and a fluid tip at the front, a fluid needle through the middle, a trigger, an air valve, two control knobs and an air inlet. The paint is held in a cup with a lid.

What does the air cap do on a spray gun?

It is the cap at the very front, round the fluid tip. The compressed air leaves the gun through it and breaks the paint into a fine spray.

What is the fluid needle for?

With the fluid tip it makes the valve for the paint. The fluid control knob behind it sets how much paint comes out.

What do the knobs on a spray gun adjust?

One sets the amount of paint and one sets the shape of the spray, from a round pattern to a flat fan. Some guns have a third control for the air.