Plastic machining turns and mills engineering plastics such as nylon, POM (Delrin), PTFE, UHMWPE and PEEK into bushes, gears, seals, rollers, insulators and fixtures. It needs no mould, so it suits prototypes and small to medium batches. Plastics move with heat and moisture, so tolerances and tools are chosen differently from metals.
Quick facts
- Common plastics
- Nylon, POM (acetal), PTFE, UHMWPE, PEEK, acrylic, polycarbonate
- Processes
- CNC turning, milling, drilling, routing
- Typical tolerance
- About ±0.05–0.1 mm (±0.0020–0.0039 inch); tighter on stable plastics
- Tools
- Sharp, polished cutters with large rake
- Moulds
- Not needed
- Usually priced
- Per part, mostly material plus machine time
Which plastic holds size best
| Plastic | Stability | Notes |
|---|---|---|
| POM (Delrin) | Very good | Best for precise parts |
| PEEK | Very good | High temperature, costly |
| Nylon | Fair | Absorbs moisture and grows |
| PTFE / UHMWPE | Low | Soft, moves with heat |
What to send
- Drawing with tolerances (allow wider tolerances on soft plastics)
- Plastic type and grade, including fillers
- Working temperature and contact with water or chemicals
- Quantity
Need plastic machining done?
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Questions
- Machining or moulding for plastic parts?
- Machining for prototypes and up to a few thousand parts; injection moulding when quantities pay for a mould.
- Why do nylon parts change size?
- Nylon absorbs moisture from the air and swells. POM is better where size matters.
- Can plastic parts hold tight tolerances?
- Stable plastics like POM and PEEK can hold about ±0.02–0.05 mm (±0.0008–0.0020 inch) on small parts, measured at room temperature.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 23 October 2026.