Boring is a reducing procedure that uses a drill little bit to reduce an opening of round cross-section in strong materials. The drill bit is typically a rotary reducing tool, frequently multi-point.
In rock boring, the opening is generally not made with a circular reducing motion, though the bit is typically turned. The hammering action can be performed from outside the opening (top-hammer drill) or within the opening (down-the-hole drill, DTH).
In uncommon cases, specially-shaped little bits are utilized to cut openings of non-circular cross-section; a square cross-section is possible. 2]