Milling machines perform a variety of tasks from simple ones like drilling and slotting to more complex jobs. They offer more accuracy and precision than lathe machines but less than routers.

Bed mills are generally more rigid than knee mills and can handle larger and heavier workpieces. However, they can't move as quickly as a knee mill.

Variable Speed Spindle

A variable speed spindle uses less mechanical components, requiring less maintenance and generating less heat which improves machine accuracy. They also use significantly less electricity, reducing your utility bills. They have a substantial knee and saddle as well as a "quill" that travels vertically on the dovetail of the column to act as a second Z-axis, allowing you to drill.

This feature makes knee mills more flexible for a wide range of machining applications than bed-type mills. For example, if you need to do jig bore work on a large plate you can swivel the head and tram it into the plate without repositioning the machine, unlike with a traditional sign-plate style mill that requires the purchase of an expensive rotary table. This flexibility also allows you to quickly change from milling a flat surface to drilling holes and tapping with the same machine, saving time.

Slab Cutter

In addition to milling slots and slits, the cutter can also cut bevels, radii, and other complex sections. This feature allows the mill to function as a shaper as well as a grinder, adding to its versatility.

Bed mills typically have a greater capacity than knee-type machines, making them better equipped to handle heavier and larger workpieces. Their rigid construction and stability also enable them to achieve higher levels of accuracy and precision than knee mills. A "knee mill" was invented in 1936 by a bed and knee milling machines builder. His creation, the Bridgeport, is famous for its durability and versatility. It remains popular today although the company that produced it no longer exists. Many other machine builders have copied its design. The American Precision Museum has a Bridgeport on display. The machine has locks that pull the knee back to a dovetail slide when you're ready to use it. It takes a little practice, but it's very easy to operate.

Electronics

Milling machines are used to machine flat, curved, or irregular surfaces by cutting the workpiece with a rotating cutter that contains mutiple cutting edges. These machines can be operated manually or motorized. They are also equipped with a table from which the work is mounted by strap clamps, vises, or chucks. They can perform milling, drilling, tapping, keywaying, facing and pocketing operations.

Knee mills are smaller and lighter than bed mills, making them easier to maneuver in a workshop or factory. They are also more versatile because the knee can be adjusted vertically to enable the head to reach areas that would otherwise be impossible with a conventional bed-type mill. However, this flexibility comes at the cost of rigidity and stability. If you need to make contoured or angular cuts, a conventional bed-type mill may be the better option. The more specialized features of these machines mean they are more expensive than knee-type models. This is why it is important to carefully consider your machining needs and choose the right model for your application.