Caring for Your Spray Gun

Caring for Your Spray Gun               [18.10.10]

 

(From DeVilbiss Service Bulletin SB-2-001-F)

Cleaning, basic maintenance and lubrication

 

Remove the air cap from the gun and immerse it in clean solvent.  Blow it dry with compressed air. If the small holes become clogged, soak the cap in clean solvent.  If reaming the hole is necessary use a toothpick or some other soft implement.  Do not clean holes with a wire or similar hard object, as permanent damage can be done resulting in a defective spray pattern.

Cleaning a Suction or Pressure Feed System

Turn off the air to the gun, loosen the cup cover and remove the fluid tube. Holding the tube over the top of the cup, pull the trigger to allow the paint to drain back into the cup.  Empty the cup and wash it with clean solvent and a clean cloth.  Clean off the outside of the tube.  Fill halfway with clean solvent and spray it through the gun to flush out the fluid passages.  Then remove the air cap and clean it as previously explained before replacing it. Wipe off the gun with a solvent-soaked cloth, or if necessary, brush the air cap and gun with a fibre brush using clean-up liquid or thinner.

Cleaning a Pressure Feed Gun With Remote Cup or Tank

Turn off the air supply to the cup or tank.  Release material pressure from the system by opening the relief valve.  Material in hoses may be blown back.   The lid must be loose and all air pressure off.  Keep the gun higher than the container, loosen the air cap approximately 2-3 turns, hold a rag over the air cap, and trigger the gun until atomizing air forces all material back into the pressure vessel.

Back-flush the hose into the cup or tank with solvent and dry compressed air.  Clean the container and add clean solvent. Pressurize the system and run the solvent through until clean.  Atomizing air should be turned off during this procedure.

Clean the air cap, fluid top and tank.  Reassemble the system.

Note:  Never soak the entire gun in cleaning solvent.  This will dry out the packing and remove lubrication.

Lubrication

Lubricate (daily) the fluid needle packing, the air valve packing, the trigger bearing screw and the adjusting screw threads with spray gun lube.  The fluid needle spring should be lightly coated with petroleum jelly.  Thoroughly clean the air cap and baffle threads and lubricate with spray gun lube. Lubricate each of these points after every cleaning.

 

Parts replacement

 

Always refer to the exploded view of your gun.

Pull trigger or remove fluid adjusting screw prior to tightening the tip to avoid damaging both the tip and the needle. Spray guns have some combination of plastic, copper, leather and soft packings and gaskets.  It is recommended that these be replaced if the assembly is removed or when dong an overall repair. The fluid needle packing must be replaced when the packing nut bottoms out. New packing or needle should be oiled before assembly.  Packing nuts should be tightened just enough to seal.  Too tight will bind the needle as well as shorten the life of the packing. When replacing the fluid tip or fluid needle, it is recommended that they both be replaced at the same time.

Please let us know if Columbia Industrial Supplies can answer any questions you may have or if you would like further information about the paint spraying equipment we stock.

Using a Wet Mill Gauge

Measuring wet film thickness

 It is important to have a good “read” on the actual wet thickness of your coating application.     

 Using the Gauge

When you spray finishes, the wet mil gauge helps you to get consistently good results. It is about the size and shape of a credit card[1]. It has a number of cutouts on each side that become progressively shorter by 1mil increments (about the thickness of a sheet of paper). On your gauge you will see the numbers 1-6 and 7-12 on the sides, and 14-30 and 35-80 at the top and bottom. Each of these tabs is labeled to indicate how far they are from the surface you set the gauge on.

 To use the gauge, you first spray a flat surface and immediately set the gauge on the wet finish (this is easier to do on horizontal surfaces). You then lift the gauge and count the impressions it left in the finish.

 Reading the Gauge

When you lift the gauge, you will see a number of impressions in the wet finish (they will disappear). Count the number of marks in the finish, not including the ends where the gauge feet contacted the surface. The number of impressions will tell you how many of the mil tabs touched the finish. This in turn tells you how thick you sprayed the finish.

 After counting the marks, use a clean cloth to wipe the gauge clean. If you allow finish to build up on the measuring tabs you will get incorrect readings from the gauge. After using the wet mil gauge for a while, you will get an “eye” for how the finish looks when sprayed at the recommended thickness.

 Caution

Most finishes used on furniture are sprayed in the 1-5 mil range, though some will be applied thicker. If you have thinned the finish to adjust its viscosity, you will have to spray thinner coats to avoid runs and sags.

 Be sure to consult the data sheet or your Columbia Industrial Supplies sales representative for the recommended mil thickness of your finish. Your finish may also have a maximum number of coats you should apply.


[1] If you don’t have a gauge, we would be happy to supply one for you.