Plastic selection
PEEK, Delrin (POM) and acetal look similar on a drawing and behave very differently in service. The choice is driven by temperature, chemical exposure, wear and how much the part can move.
Quick comparison
| PEEK | Delrin / POM | POM-C (acetal copolymer) | |
|---|---|---|---|
| Continuous temperature | Up to ~250 °C | Up to ~90 °C | Up to ~90 °C |
| Strength and stiffness | High | High | High |
| Chemical resistance | Excellent, wide range | Good, but attacked by acids and chlorine | Good, similar to POM-H |
| Moisture absorption | Low | Low | Low |
| Machinability | Good, but heat-sensitive | Excellent | Excellent |
| Relative material cost | Very high | Moderate | Moderate |
| Typical use | Seals, insulators, medical, semiconductor | Gears, bushings, wear parts | Gears, housings, general parts |
Typical values. Check the supplier datasheet for the exact grade and condition.
PEEK: when the part cannot fail
PEEK is the choice when the part sees high temperature, aggressive chemicals, or a critical application where a failure is expensive. It is also the choice when the part must be clean and low-outgassing — semiconductor, vacuum and medical-adjacent components. The trade-off is price: PEEK can cost 10–20× more than POM, and it machines slower because heat builds up and the part moves after machining.
If you specify PEEK, specify the grade (natural, black, GF30, CF30) and the annealing requirement. The same drawing in GF30 can cost more and behave differently from natural PEEK.
Delrin / POM: the default for wear parts
POM is the default for gears, bushings, rollers, wear pads and general mechanical parts. It machines beautifully, holds a tolerance, has low moisture absorption and is available in rod, plate and sheet. For most indoor mechanical parts under 90 °C, POM is the economical choice.
POM is not the choice for strong acids, chlorine or hot water. It also has a reputation for poor adhesion; if the part needs bonding, plan the joint or choose another material.
PEEK vs POM: the decision in one table
| Question | If yes | If no |
|---|---|---|
| Does the part see more than 120 °C? | PEEK | POM |
| Is it exposed to strong chemicals or steam? | PEEK | POM may work |
| Is it a critical seal or insulator? | PEEK | POM may work |
| Is the part a gear, bushing or wear pad under 90 °C? | POM | Consider PEEK only if the duty demands it |
| Is cost the main constraint? | POM | PEEK |
When the answer is mixed, test one part in the real environment before committing to a production run.
Machining notes
- PEEK: sharp tools, low surface speed, coolant at the cut, and annealing before the finish pass on tight-tolerance parts. Measure at a stated temperature.
- POM: standard carbide tooling, good chip control, watch for stress in thin walls. It machines close to free-cutting brass.
- Both: do not share fixtures with metal parts if cleanliness matters. PEEK and POM pick up chips and oils.
Send the drawing with the environment and the duty cycle. We will tell you which material we would use, and where the risk is. PEEK machining · PEEK material data · Delrin · Acetal (POM).
Written by the engineering team at GY Machining, Dongguan. We machine prototypes and production parts in aluminum, stainless, titanium, brass and engineering plastics.