Horizontal boring mills and vertical boring mills performs a variety of drilling and boring operations on large parts. The two types differ in workpiece and tooling setup but with the same basic functionality.

A horizontal boring machine or horizontal boring mill is used for horizontal boring on large parts. The spindle is parallel to the ground and the work table. Horizontal boring machines are mostly used for the roughing out of large parts with high precision.

Vertical boring mills, also known as vertical turret lathes are mostly used for machining of large circular or round parts like turbines components, pipe flanges etc. Vertical boring mills can perform most lathe operations like facing, boring, turning, tapering and thread cutting.