Machining plastics looks like machining metal until it does not. Plastics cut faster and easier, but they also heat up quickly, move after you cut them, and chip if you push too hard. These are the practical points that separate a clean part from scrap.
Start with sharp, polished tooling
Use tools intended for plastics or aluminium: sharp, high-positive-rake geometry with polished flutes. Dull or rough tools rub instead of cut, and rubbing means heat — the number one cause of melted or gummy finishes.
Keep it cool
- Use generous coolant or strong air blast to clear chips and carry heat away.
- Take light, fast passes rather than deep slow ones.
- Do not dwell in the cut — keep the tool moving.
Expect the material to move
Plastics are elastic and, in Nylon’s case, moisture-sensitive. A part can measure perfectly on the machine and be out of tolerance the next day. For tight work: rough machine, let the part rest and stress-relieve, then finish. Acclimatise stock to the shop environment before cutting.
Clamp gently
Plastics are soft. Vises and clamps can deform a part before the cutter touches it, and the spring-back throws off your final dimensions. Use soft jaws, spread the clamping force, and support thin sections.
Common mistakes to avoid
- Using metal feed/speed settings and burning the surface.
- Leaving chips in the cut so the tool recuts them — produces a rough finish.
- Deburring with too much pressure, which melts a rolled edge instead of cutting it.
- Measuring immediately on a warm part.
Need a machined plastic part?
We machine PTFE, POM, Nylon, HDPE, UHMWPE, PP and Bakelite to print — from one-offs to production runs. Send us your drawing and tolerances and we will quote it. Get a quote.