An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit in its application, geometry, and manufacture. While a drill bit can only cut in the axial direction, most milling bits can cut in the radial direction. Not all mills can cut axially; those designed to cut axially are known as end mills.
End mills are used in milling applications such as profile milling, tracer milling, face milling, and plunging.
There are four critical angles of each cutting tool: end cutting edge angle, axial relief angle, radial relief angle, and radial rake angle.
Depending on the material being milled, and what task should be performed, different tool types and geometry may be used. For instance, when milling a material like aluminum, it may be advantageous to use a tool with very deep, polished flutes, a very sharp cutting edge and high rake angles. When machining a tough material such as stainless steel, however, shallow flutes and a squared-off cutting edge will optimize material removal and tool life.
A wide variety of materials are used to produce the cutting tools. Carbide inserts are the most common because they are good for high production milling. High speed steel is commonly used when a special tool shape is needed, not usually used for high production processes. Ceramics inserts are typically used in high speed machining with high production. Diamond inserts are typically used on products that require tight tolerances, typically consisting of high surface qualities (nonferrous or non-metallic materials).
In the early 90s, use of coatings became more common. Coatings can provide various benefits including wear resistance, reduction of friction to assist with chip evacuation, and increased heat resistance.
Most of these coatings are referred to by their chemical composition.
Single: Is used to remove lots of material at a very fast rate. Traditionally used in a roughing operation.
2 Flute: Allows for more chips to be removed from the part. Primarily used in slotting and pocketing operations in non-ferrous materials.
3 Flute: Similar to the 2 Flute end mill but can be used to cut ferrous and non-ferrous materials
4+ Flute: Designed to run at faster feed rates but due to having more flutes it causes issues with chip removal.