Plastics are very well suited to, and now widely used in, many industries, just like metals, thanks to their strength and flexibility. Just like metals, plastics are machined on equipment such as milling machines and lathes: although the process is similar, care is needed and the right adjustments must be made when moving from metalworking to machining plastics. Plastics have their own specific mechanical and chemical properties and must be machined appropriately to get satisfactory results.
There are several plastics processing methods used in industry to produce sheets, bars, profiles, rollers, bushings and many other components, in every way similar to those made of metal. The most common processes for plastics include various types of moulding – injection, compression and transfer moulding – as well as extrusion, pultrusion, calendering and so on.
One of the most widely used plastics is PTFE (Teflon): this material, known for its lightness and insulating properties, can actually be machined like a metal, on a milling machine or a lathe, as long as specific precautions are taken.
Turning PTFE: how to do it
First of all, machining PTFE requires sharp, positive-rake blades and cutting edges, run at high speed. PTFE cuts easily, but care is needed because it also chips easily. The advice is to take shallow cuts, especially when finishing, when the speed should also be reduced slightly to avoid distorting the part.
PTFE machined in this way can be used to make low-friction mechanical parts and electronic parts with high insulating properties that resist very high temperatures, up to around 260–300 °C.