To add hole sets to an element tree, first, obtain the hole set number by calling the function ProNcseqElemHolesetAdd(). This hole set is used to reference a set of holes with the same properties, including depth, direction, countersink diameter, and so on. Note that feature element PRO_E_HOLESETS has limited support for drill point sets, but allows the user to identify and to delete existing drill point sets in a feature, or to overwrite drill point sets with drill axes sets.

For example, you might want one set of holes to be countersunk to a diameter of 10mm, and another set to 14mm. Because these countersinking operations are done with the same tool, they should be in the same NC sequence. Because the countersink diameter is different for each, you should create two hole sets.