Hand speed has a lot to do with it, I can line just fine with the volts set to 8.5 to 12.0. You really need to let the needle fill the skin up with a good amount of ink. There is a fine line with going to slow or to fast, and using your stretching hand to feel the vibration the needle is making on the skin. This allows you to see what the needle is doing with your mind, I know when a line is going to look good or bad before I even wipe the ink away.