there are calculations called speeds and feeds, they are based on the perfect cutting speeds for each material and the size of material being machined. all materials, whether it is metal or plastic based, have an optimum cuting speed as well as what coolant that should be used, also what characteristics should be used when grinding the angles on your cutting tool. it is a science that has been investigated over many years. time served machinists will know all of this stuff, look on the net for more info.