Pilot drill diameters turns on and sets a list of drill sizes used to drill pilot holes. Specify a list of diameters with a comma between each drill size. Specifying .5, 1, 1.5 in inches for example causes holes to be pilot drilled with the half inch drill for final hole sizes up to an inch. A hole in excess of 1.5 inches would be pilot drilled with all three of the specified drills before being drilled to size. No list of drill sizes turns off pilot drilling for the feature, although this attribute can also be set up as a default for all parts.