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How to: Set Up Your Auto Spray Gun Properly

Your spray gun is the essential tool when refinishing an auto. Setting your gun up correctly is a critical part of any paint job. Here are three tips on how to prepare your gun properly for spraying.

Be sure you have enough air supply

HVLP (High Volume, Low Pressure) guns need a high air volume to operate. If you are unsure what cfm (cubic feet per minute) is required for your gun to operate correctly, consult the instructions or call the gun’s manufacturer? A good compressor, set at 90 psi, will provide the necessary constant pressure.

In addition, check the regulator attached to the base of your gun to be sure it is set correctly. You can filter out any water or oil in your air lines by adding a small disposable air dryer on the end of your gun.

Choose the correct cap, tip, and needle for your spray job

The cap, tip, and needle you use on your gun will depend on the kind of spraying you are doing. Primer spraying requires a 1.8mm tip and cap. That will allow the gun to use a thicker spray than the one you use for clear coat or body paint. Base coat paint requires a 1.4 mm tip and cap. The clear coat can be applied with a 1.3 for a smooth orange peel free finish, or a 1.4 mm tip for a finish with a little orange peel. Urethane sealers such as the GLM2640G Urethane Sealer Grey should be applied with a 1.5 mm tip and cap. Consult the paint manufacturer’s instructions if you are unsure of the correct caps, tips, and needles to use.

Set your gun before each use

Humidity and temperature can affect how your gun works. Each day, before beginning to spray, adjust your gun air pressure and fan control by testing the spray against a piece of masking paper taped to the wall. Here’s how to set the air pressure and volume of your paint gun:

Set your gun’s air regulator at 50 psi.

Close the air volume control knob (usually located beside where the air hose enters the gun). Then, with the trigger pulled, open it to the point where the air volume starts to stay the same, and then stop.

Your air pressure and volume are now set.

To set the fan control…

Open up the fan control (located on the top or side of the gun) all the way while pointing the gun at the paper. Then, turn it down until your spray is about 15cm tall (6 inches) with the gun about 15cm (6 inches) from the paper. You should see a cigar-shaped pattern on the paper. If you don’t see a cigar-shaped pattern, you must dis-assemble your gun, removing the needle, cap and tip as well as the nozzle, with your paint gun wrench, and clean with GLM100 True Blue Paint Gun Cleaner. Retest your spray pattern and clean again if you do not see the cigar shaped spray pattern.

Your fan control is now set.

Since a normal spraying distance is 20 to 22 cm, test your spray against the paper at this range to be sure that the spray pattern remains fully covered without any runs.

Note: If you have to change the psi at the cap (going from primer to body paint or clear coat), you will need to calibrate the settings again. It is best to have a separate spray gun for primer, sealer, base coat, and clear coat.

Follow these tips to set up your gun each day and you’ll get a great auto paint job.