To set a liner: When setting your machine to be used for lining, you would need to install a small μμF rated capacitor, thick guage springs, and a light armature bar.
To set a shader: When setting your tattoo machine to be used for shading, you would need to install a large μμF rated capacitor, thin guage springs, and a heavy armature bar.
To help you understand how this affects your lining tattoo machine, basically the smaller the capacitor rating the faster the discharge from the cap will be, Causing faster cycles per second (cps). The tighter or thicker the contact spring the less give it has and returns to it's starting position hence a faster cps. The lighter the armature bar the less effort on the spring to pull it back up increasing the cps. The inverse is also true for a shader set up.
You could also adjust the gap between the contact screw and the spring is an old solution that is a littleoutdated. The gap can be as wide open or closed as you want it as long as the tune is set correctly. With the recent advancements in capacitor technology and the ability to cut springs of different guages it has changed the way you set a machine. This worked when all you had was one guage for springs and used whatever cap (if any) you could find. If it works for you wide open to line or shade it's how you work and that should be enough.
Notice the placement of the contact spring, this causes there to be more movement as the spring and armature bar will move more freely meaning a slover CPS, ideal for shading.