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Plug the air compressors air line into the base of the DeVilbiss spray gun; it has a universal fitting that locks into the air line. You will see the air pressure gauge at the base of the gun register the overall air pressure from the compressor when the line is properly inserted.

Adjust the knob at the base of the DeVilbiss spray gun until the dial indicator registers 20 pounds per square inch. This is the optimum spraying pressure for enamel paint.

Pull the trigger of the spray gun. The trigger should pull back within 1/2-inch of the handle. The spray adjustment knob is located at the top and the back of the spray gun; turning the knob counterclockwise will reduce the amount of play in the spray guns trigger, thus reducing the amount of paint allowed into the sprayer.

Locate the knob on the side of the spray gun. On a DeVilbiss HVLP, this knob controls the width of the spray pattern of the gun. Adjust this knob all the way counterclockwise to open the spray pattern all the way.; at this setting, when spraying 12 inches from the surface, the spray pattern will be 12 inches wide.

Locate the knob just above the webbing of your thumb and forefinger when holding the spray gun; this knob controls the air pressure of the gun. Turn the knob all the way clockwise to open up the gun completely. Because you have a pressure reading of 20 PSI from the air control knob, you do not need to further restrict the air flow.

Thin the enamel paint with a 4:1 ratio of paint to enamel thinner; this is the accepted standard for spraying enamel paint through a 20 PSI spray gun. You should doublecheck the paint data sheets to make certain, though, as some paint manufacturers may produce their paint slightly thicker or thinner, and will recommend a different optimal pressure accordingly.

Turn the air compressor on and let it achieve operating pressure. The air compressor will cycle off when it is ready for use.

Hold the impact gun with the bottom quick connector facing up. Squirt two or three drops of pneumatic tool oil in the connector.

Grasp the quick coupler on the impact gun at the rear. Pull the ring back and insert the air compressor hose onto the tool. Attach the other end of the hose to the air compressor in the same manner.

Insert a socket into the impact gun by pressing it on the tip.

Turn the airflow regulator on the impact gun to a higher number and setting for more power. If the socket is on a bolt and the bolt will not turn, adjust the tool for more torque to a higher number. Turn the airflow regulator to a lower number and setting for less torque.