A milling tool is a large cutting and drilling device that takes material, usually metal, and cuts into it to make holes, smooth out sides, or create indentations in the material so the piece can be fitted with other pieces. There are two major milling tools: a vertical milling machine and a horizontal milling machine. There are also two types of vertical milling machine units: bed and turret. The cutting piece is arranged vertically on the mill and drops down to cut into the material.
The vertical milling machine tool, regardless of subcategory, refers to a milling tool in which the cutting piece is vertically arranged. It only moves up and down, or vertically. The table part moves according to the operator’s instructions, so the material can receive curved cuts or different finishing cuts.
There are two vertical milling machine subcategories: bed and turret. The difference between them is how the table moves. With bed mills, the table only moves against the cutter’s axis, while the turret variety moves with and against the cutter’s axis. Turrets are used more often, because they are able to move more freely, but bed types are often used for larger machines.
Most vertical milling machine tools come with a combination of automatic and manual controls. On the automatic side, the operator is able to change the speed of the cutting mechanism, decide whether the cutter should go in forward or reverse, and control the on and off switch. The manual controls are handles and wheels that change the angle and height of the table. To help control accuracy, there is often a digital monitor that shows the angle of the table, which helps operators when a cut has to be precise.
There are two different cutting directions — up and down — on a vertical milling machine. Up is the conventional cutting direction and is best used on thick pieces of metal. Down is used less often but the cut is better. While the cut is higher quality, downward cutting is only good for thin pieces of metal and using this on thicker pieces can damage the cutter.
In contrast to the vertical milling machine, there is a horizontal milling machine. The cutting unit is attached on a horizontal bar and the cutter moves from left to right. These units are better for making shapes on the sides of the material, rather than for making holes. The table on horizontal mills usually offers less control than with a vertical milling machine.