How to make a homemade tattoo gun in six easy steps. Find a cassette motor or similar type rotary motor that runs on 12 volts. Use a mechanical pen that will serve as the tube that will guide the needle bar. Take a teaspoon and bend the end back at the narrow neck just before the wide piece and is cut off leaving an L shaped bar. Use a straightened E string from a guitar cut to the length of the tube from the center of the motor to the tube after assembly. Sodder a beading needle that has been cut to 1.5 inches. Use a multipower adapter so variable amounts of power can be used. You can find more information here: http://www.wonderhowto.com/how-to-make-a-homemade-tattoo-gun/
Bend a piece of guitar string. Take the ink tube out of a pen and file down the brass tip to get the ball out. Insert a needle into the pen. Then cut a toothbrush to about 4' and bend. you have to heat it to get it to stay. Tape the pen to the toothbrush. Attach to a motor with an eraser and find a power source.