Milling cutters that are coated can have a great influence on the performance of a cutter, it increases the cutting speed and the tool life, and it also improves the surface finish of the machined face. Polycrystalline Diamond (PCD) is an exceptionally hard coating used on cutters which need to withstand high abrasive wear. A PCD coated tool can last up to 100 times longer than an uncoated tool. However the coating is not suitable for temperatures above 600 degree C, it is also unsuitable for non ferrous metals such as brass and aluminium. Tools for machining aluminium are sometimes given a coating of TiAIN. Aluminium is a relatively sticky metal and can weld itself to the cutters teeth causing it to appear blunt. However it tends not to stick to TiAIN, allowing the cutter to be used much longer on aluminium. There are many coatings for cutters on the market, each with their own application of which it has been specifically developed for. There are specification charts now available, giving the machinist various options of cutters and their coatings, these are very helpful when buying milling cutters, knowing that the right cutter has been purchased for the right material.
