Knee Milling Machine Guide

Some History

The knee milling machine is a dinosaur in the world of manufacturing. However, opposed to T-Rex this machine tool classic is far from going extinct. Rudolph Bannow was the man who produced the first industrial knee and column vertical mill with a rotating turret in 1936. His company's name, Bridgeport, became a synonym for this kind of vertical mill. And even today, with all the CNC machining centers becoming more and more affordable even for small machining shops, traditional knee mills are still running strong!.

The Moving Table Advantage

A knee milling machine is a relatively simple kind of vertical mill. The special feature of the knee mill is that additionally to the horizontal X-axis it can move along the vertical Y axis, too. In other words, the worktable is not fixed but moves along the machining axis, just like the workpiece itself. The spindle head of the knee mill performs all cutting operations on the Y-axis. Sometimes knee mills are also called Bridgeport mills. This stems from the renowned manufacturer that popularized this type of vertical mill for hobbyists and small shop owners. Thanks to the ability to adjust the head along the X-axis the knee mill is a very flexible machine tool suitable for a wide range of operations and workpiece types.

As mentioned above, the most unique feature of knee mills is that they are equipped with a vertically adjustable worktable. As the name shows, the worktable is rested on a knee-supported saddle.

The knee is a kind of supportive and massive casting. The main function of the knee is that it can ensure the stability of a knee milling machine by riding vertically on the column. Also, it can clamp the column rigidly and firmly in a fixed position. This is for making the milling head and spindle be vertically fixed during operations.

Versatile and Reliable

For modern vertical machines, the spindle isinstalled vertically, e.g. parallel to the column face. The purpose of applying the design is for the entire head to have the ability to swivel on angular surfaces. The way of the turret and swivel head assembly gives cuts a higher precision and mobility (sometimes an object has to be swung 360° on the base). For angular cuts, the setting of the head permits better precision when it is done on the horizontal plane. The versatility and stability of knee milling machines make it one of the most popular manufacturing machines in recent years. The brief introduction mentioned above simply shows a part of its capacity.

Why is it still so popular?

knee milling machine
Fig.1 Traditional Mill Close-up
 

The knee milling machine is still one of the most widely used machine tools in machine shops around the globe. Machinists just love the unenclosed nature of the machine as it allows for quick setups for simple jobs. Just put a workpiece into the mill, drill a couple of holes or tap something, and boom, the part is done. Also, the tiltable head, movable ram, and turret make it extremely versatile for its work envelope. the machine is versatile and allows for a flexible work envelope.

Ease of use

The operation with this type of manual mill is relatively easy to learn for anyone with the right instruction. It is often the best starting point for newcomers in the machining industry. You don’t have to write code or set up complex tooling programs. All it takes is equipping the collet with a drill or endmill and off you go. This is why the knee mill is still one of the favorite machine tools for machinists and metalworking enthusiasts around the world.

Knee Mill Applications

A CNC knee mill can perform an incredibly wide variety of cutting and forming processes. It is also suitable for different workpiece sizes only limited by the knee travel. Some of these processes include surfacing, cutting, and slot machining. Such a wide range of forming capabilities is also possible due to milling tools, which are very similar to drill bits. These metalworking tools come in many different shapes and sizes, all of which cut different-sized shapes when used.

The knee mill can be very beneficial when it comes to machining larger objects. In some scenarios, a moving spindle will not provide enough torque to drill vertical holes, a process also known as boring. Knee mills have stationary spindles, and all y-axis movement happens alongside the workpiece. This arrangement results in a significant torque increase, making it possible to drill holes in hard material. Another benefit to the knee mill is also a result of the vertical movement of the table, as larger objects can also be machined, due to an increase in height capacity.

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