I have cut off pressure set at 60 psi, switch won't close until pressure drops below 30 psi. I would prefer a differential of about 15 psi.

With power off, turn the small nut three turns counter clockwise. Turn the power back on and cycle the pump by running water. The cut off pressure will be less. Keep at it until you have the fifteen pound differential you want.

At that point, you might decide that a cutoff of forty five pounds is a little low. If so, turn the large nut three turns clockwise. That will raise both the cuton and cutoff points and maintain the fifteen pound differential.

Check this site out for some really good info: How to adjust water pump pressure, pump cut-on pressure and pump cut-off pressure - private pump and well system do-it-yourself repairs (http://www.inspectapedia.com/water/Pressure_Switch_Nut_Adjust.php)