In vertical mills such as mini-mills, the primary cutting tools used are end mills. End mills are shank-type Milling cutters used in variety of industrial milling applications such as profile milling, tracer milling, face milling, and plunging. As a metalwork cutting tool, in order it to perform a lengthy period of time, end mills need to be made of materials that are harder than the materials that they are being used to cut.
Older, more traditional end mills were made from high speed steel. More modern end mills are made from tungsten carbide. However, some end mills are made out of different kinds of carbide. These include tantalum carbide and titanium carbide. Carbide milling cutters, such as carbide end mills, are more resistant to friction and wear-and-tear than high speed steel end mills. However, even carbide end mills wear down eventually.
In order to make carbide cutting tools like end mills even more resistant to wear-and-tear, they are chemically coated. Such end mill coatings are referred to by their chemical composition. A few examples are: TiN (a basic yellow coating no longer widely used), TiCN (a widely used bluish-gray coating), and TiAIN (a very popularly used dark purple coating).
PCD veins in end mills are also worth noting though they are not coatings. Several end mills are manufactured with a vein of polycrystalline diamond that was formed from a high temperature-high pressure environment. The vein itself gets formed in a blank and the material is then ground out along the vein to form a cutting edge. While the tools for this can be expensive, these veins help end mills last longer than many other cutting tools.
End mills come in various styles and various qualities. The most common end mills in use are two-flute and four-flute end mills. A flute, within the context of cutting tools, is a recessed portion of that cutting tool’s cross-section whose purpose is to convey chips away from a cutting edge as the cutting tool rotates.
Also, end mills are specialized for certain tasks such as the ball end mill. This end mill has a round tip for milling grooves with a semi-circular cross-section. Additionally, end mills are also available in different shank sizes. A shank is the smooth portion of the end mill’s shaft above the cutting edges. End mills of different diameters within a range have common shank sizes, but shank sizes vary among larger and smaller end mills.
Anyone interested in cutting tools or shopping at an end mill store should know the differences between two-flute end mills and four-flute end mills. Two-flute end mills are mostly used for cutting slots or grooves. Four-flute end mills are more often used in surface milling, using the end of the mill.
Furthermore, a two-flute end mill, sometimes called a slot mill, is designed for plunge milling. This means exactly what it sounds like. It plunges right into the work. Two blades sit at the business end of the cutter with one of the blades going right across the middle. This allows the cut tool to mill directly underneath it. It can cut vertically or horizontally, but horizontal cutting is better left to a four-flute end mill.
Four-flute end mills are not designed to be plunged. Their blades are of the same length, but with a hole in the middle where nothing can be cut. This type of end mill can only cut horizontally. The type of job determines the type of end mill to be used.
