A horizontal boring machine, also known as a horizontal boring mill, is a machine tool that is used to bore holes in a horizontal direction. Unlike a vertical boring machine, where the spindle is in a vertical position, the spindle in a horizontal boring machine is in a horizontal position. This allows the machine to access the underside of the workpiece and to bore holes from that angle.

Horizontal boring machines can be used to bore holes of varying diameters and depths, and they can also be used to mill and drill. They can be equipped with a variety of different cutting tools, including drills, end mills, and reamers, and they can be used to create a wide range of features on the workpiece, such as grooves, slots, and other complex geometries.

The workpiece is mounted on a table, which can move in a variety of directions and is equipped with a boring head that is connected to the spindle and is able to move in a horizontal direction. This allows the cutting tool to approach the workpiece from a variety of angles, and to reach all parts of the workpiece.

Horizontal boring machines can be found in various industries such as construction, mining, energy and heavy equipment manufacturing. They are particularly useful for large and heavy workpieces that cannot be easily rotated, or for workpieces that have already been assembled. Some horizontal boring machines are also equipped with a rotary table that can rotate the workpiece to provide multi-axis machining.

Horizontal boring machines require skilled operators and specialized tooling to produce precise and accurate parts. They are also relatively expensive, and require proper maintenance and calibration to ensure accurate and precise boring.