Chip loads are provided as ranges. In order to extend the life of your tool, use the lower value in the range. If need to get your job done quickly then you can a higher chipload within the specified range.

Tap feeds and speedschart

Use a plunge rate of 50% or less of the feed rate. So for a feed rate of ... ft/min, use a plunge rate of ... ft/min or less.

Tap feeds and speedspdf

Feed Rate = Spindle Speed (RPM) * Number of Flutes * Chip Load (inches) = Spindle Speed * Number of flutes * Chip Load = Answer inches/min