Line boring or line drilling is a machining process to create or enlarge parallel and straight holes in materials such as wood or metal. This process is carried out using a special line drilling machine which has high precision.

Line boring has several uses, including:

• Making two or more holes in one component so that they have the same diameter and mutually intersecting axial axes.
• Repair worn holes or surrounding holes.
• Create perfectly straight and parallel holes for the camshaft housing, crankshaft and saddle.
• Line bore is often carried out on several large engine parts, such as: engine blocks, gearboxes, press machines, turbines.
• Unfresh holes in machine components can cause vibration, misalignment and system malfun.