Endmills

An endmill is a shank-type cutting tool used in industrial milling. It is distinguished from the drill bit because a drill bit can only cut in the axial direction, where a milling bit can generally cut in all directions with some exceptions. Several categories of endmilling tools exist divided by specific application, and special geometry tool design requirements. Traditional solid endmills are being replaced by more cost-effective inserted cutting tools which have a greater initial cost, but greater longevity and easier replacement of worn or broken cutting edges.

Endmills are available in both imperial and metric shank and cutting diameters. The material being milled, and what task should be performed determines the necessary tool types and geometry required. Endmills are now most often made of tungsten carbide, a rigid, wear-resistant material, usually formed from carbide powder into rods ground into blanks of industry-standard sizes. In the early 1990's the use of coatings to reduce wear and friction became more common such as titanium nitrate, a coating that prevents metal chips from sticking to the endmill which reduce its life and the quality of the cut. Some endmills have a vein of polycrystaline diamond. This vein is formed using high temperature-high pressure technology. The vein is formed in a blank and then is ground out to form the cutting edge. These tools can be expensive, but last many times longer than other tooling.

Endmills generally are made on CNC machines using high-pressure lubricants like water, water-soluble oil, and high-flashpoint oil. Grinding inside the machine is accomplished with abrasive wheels mounted on a spindle or sometimes multiple spindles depending on what material is being ground. The wheels are made with industrial diamond , cubic boron nitride, and other materials set in a bond depending upon what type of material is being worked.