Depress the armature bar--the thick metal bar above the electric coils--and examine the gap between the front spring of the armature bar and the contact screw. Set the gap for line work by turning the contact screw until the gap between the tip of the screw and the front spring of the armature bar is the approximate thickness of a U.S. dime (a little bit more than 1 mm).
Attach an appropriate needle tube to the tattoo gun. Insert the needle bar into the tube and fit the end ring of the needle bar over the rubber grommet on the armature bar. Loop a rubber band around the tattoo gun, encircling the back of the frame and the front of the needle bar, to cut down on vibration and lateral movement of the needle bar.
Examine the needle with a jeweler's loupe or magnifier while depressing the armature bar. Adjust the needle tube so that the length of needle that protrudes from the tip matches the gap of the contact screw.
Set the speed of the tattoo machine for line work. Some machines display a readout of voltage. Six volts is appropriate for lining. Most tattoo artists adjust voltage by listening carefully to the sound of the gun--it should produce a steady buzz or a hum. The sound shouldn't crackle or sound make a staccato noise such such as those made by machine guns or typewriters.
Check the needle while the tattoo gun is activated. The rapidly moving needle should look like one one solid column. If it looks like a multiple columns or you see a ghost image, tighten the rubber band on the needle bar to reduce or eliminate the lateral movement.
Set the gap between the armature bar and the contact screw for shading to approximately 2mm, or the thickness of a U.S. nickel.
Attach a needle tube appropriate for shading to the tattoo gun. Insert the matching needle bar into the tube and secure it. Examine the needle tip with a magnifier; and adjust the needle tube and rubber band properly, as you did for the lining gun.
Reset the speed of the tattoo machine for shading. Shading requires a slighty slower speed than line work. Adjust the speed by eye and ear. The hum or buzz should be a deeper sound than that made by a machine set for lining.