A horizontal milling machine is one of the two basic styles of milling equipment. These machines specialize in a process called arbor milling, which involves the rapid removal of material from a source object. These machines were the original milling machine style, with vertical milling only coming into prominence many years later. While a horizontal milling machine is still commonplace in most large manufacturing centers, vertical machines utilizing computer numerical control (CNC) are becoming more common all the time.
A milling machine is a piece of manufacturing equipment. The horizontal milling machine came into use during the early 1800s, and the basic design of a common modern machine is nearly the same as this original model. These machines may be small enough to fit on a kitchen table or as large as entire rooms, depending on the size of the item being manufactured. These machines take an initial object and remove bits, drill holes or shape contours until it is a specific size, shape and weight.
Most milling machines move the object being shaped and the tool doing the shaping. This puts these machines in a unique class, as most manufacturing equipment typically only do one or the other. There are two basic styles of milling machine: the vertical and the horizontal milling machine. They differ in design and general usage.
The main difference between a vertical and horizontal milling machine is the orientation of the spindle, the main tool inside the machine. A vertical machine operates mainly on the top and bottom of an object, although it can operate on any side. The orientation and design of many vertical machines makes them well-suited for standing operators and fine detail jobs. Since the machine operates vertically, these machines are generally taller than they are long.
A horizontal milling machine operates mostly on the sides of an object, and its positioning allows for much more aggressive material removal. These machines are often larger as well, since they are typically long instead of high. As a result, vertical machines are often used to make dies, while horizontal machines work with larger milling projects.
Many modern milling machines are moving away from the vertical/horizontal design. While these new mills are technically vertical mills, they are much more than a standard vertical mill due to their spindle rotation. These milling machines are completely computer-operated. They can rotate the object freely, working evenly on all sides. In addition, they can rotate the tool, from a standard vertical to a nearly horizontal plane—this freedom of movement creates a combination of the two standard designs.