Milling is the work of producing a flat or precision-contoured surface on a machined workpiece by using a rotating tool, and generally by taking multiple parallel passes with that tool. The work can be done on a machining center or milling machine, and can also be done on a lathe, turning center or turn-mill machine that happens to have rotary tool (or “live tool”) capabilities.
The tools for milling include both solid tools and inserted tools—the latter consisting of a tool body that uses replaceable cutting inserts. Carbide is the most likely material for milling tools, though high speed steel is another choice, as are ceramic, cermet and diamond tools in certain more demanding milling applications.
A common milling tool variety is the “end mill,” which generally describes a relatively narrow cylindrical tool that can mill on both its tip and its side, and can reach into various constrained features and spaces. The end mill can be flat-bottomed for flat surfaces, or ball-nosed for milling up, down and along the contours of complex milled shapes such as die and mold surfaces.
Another common milling tool variety is the “face mill,” a generally larger-diameter tool designed for efficiently milling a wide, flat surface in an economical number of passes.