Plunge roughing provides an alternative form of roughing. With this technique, roughing is performed with a series of overlapping holes. The advantage of this technique is parts can be roughed quickly since the force of the operation is directly up the spindle.
This figure shows a sphere that is being plunge roughed with a flat end tool.
The pattern of the drilling operations are parallel to the X or Y axes just like parallel milling. Neighboring rows of the pattern can be offset horizontally to better cover the part.