Holes - machined features

• Internal Counterbore: A recessed cylindrical feature inside a hole, typically for bolt heads or nuts to sit flush.

• External Counterbore: A recessed cylindrical feature on the outer surface, often for clearance or seating purposes.

Here’s a 3D view of internal and external counterbores:

Unlike a counterbore hole, a countersink hole features a conical shape. It consists of a simple hole with a tapered recess above it. Creating this cone-shaped recess demands greater calculation and precision compared to drilling a counterbore hole.

A counter drilled hole resembles a countersink hole but features a recess above it.