Delrin vs nylon is one of the most common engineered plastic decisions on machined parts. Delrin is DuPont's trade name for acetal homopolymer (POM-H), and acetal copolymer (POM-C) is a close relative. Nylon, most often nylon 6/6 or cast nylon 6, is tougher and handles higher temperatures but absorbs significantly more moisture. If a part must hold tight dimensions in changing humidity, acetal usually wins. If it must absorb impact or run hot, nylon often does.
Delrin vs Nylon: Comparison Table
Values are typical for unfilled grades. Cost is a relative per-part index including material, where one acetal part at quantity 1 equals 100.
| Factor | Delrin / acetal (POM) | Nylon 6/6 or cast nylon 6 |
|---|---|---|
| Relative cost, qty 1 | 100 | 95 to 110 |
| Relative cost, qty 10 | 38 | 38 to 45 |
| Relative cost, qty 100 | 16 | 17 to 21 |
| Relative cost, qty 1,000 | 9 | 10 to 13 |
| Moisture absorption, 24 hr | About 0.2 to 0.25% | About 1.0 to 1.5% |
| Moisture at saturation | About 0.9% | Up to about 7 to 8% |
| Typical machined tolerance | ±0.002 to ±0.005 in, stable | ±0.003 to ±0.010 in, moves with humidity |
| Surface finish | Ra 32 to 63 µin, clean | Ra 32 to 125 µin, can fuzz |
| Tensile strength | About 10 ksi | About 11 to 12 ksi dry, lower when conditioned |
| Impact toughness | Good | Very good, especially when conditioned |
| Continuous service temperature | About 180°F | About 210 to 230°F |
| Friction and wear | Low friction, good wear | Good wear, especially lubricated or filled grades |
| Typical use case | Precision bushings, gears, valve seats, fixtures, food parts | Wear pads, rollers, sheaves, impact parts, large gears |
When Delrin (Acetal) Wins
- Tight tolerances. Low moisture absorption keeps dimensions stable, so acetal holds machined tolerances in service.
- Low friction. Good for sliding parts, cams and small gears without lubrication.
- Machining quality. Acetal cuts cleanly with crisp edges and good finish, and it runs well on Swiss machines.
- Wet or humid environments. Dimensions change very little.
When Nylon Wins
- Impact and abrasion. Nylon absorbs shock and wears well in rough service.
- Higher temperatures. Nylon 6/6 handles more heat than acetal.
- Large parts. Cast nylon is available in large rods and plates for sheaves, rollers and wear pads.
- Filled grades. MoS2 or oil-filled nylons improve wear and lower friction.
Common Mistakes
- Specifying tight tolerances on nylon without accounting for moisture growth. A nylon part can grow roughly 0.002 to 0.003 in per inch as it absorbs moisture.
- Using acetal near strong acids or chlorine, which attack it.
- Choosing Delrin homopolymer for large thick sections where centerline porosity can occur. Acetal copolymer is often used for thick stock.
- Applying metal-style tolerances. Plastics expand about 5 to 10 times more than steel with temperature.
Machining Notes
Both materials machine well with sharp tools and good chip evacuation. Stress-relieved stock reduces warping on parts with heavy material removal. For nylon parts with tight dimensions, inspect in a controlled environment and define the measurement condition on the drawing when it matters.
How This Applies at Wexmar
Wexmar machines acetal, nylon and other engineered plastics on our CNC lathes, horizontal machining centers and Maier Swiss-type machines, which are well suited to small acetal bushings, spacers and gears to 32 mm diameter. See materials, Swiss machining, and the guide on PEEK vs Ultem.
Getting a Quote
Include the specific grade and any color requirement on the drawing. You can upload a drawing for an instant estimate, reviewed by a human estimator, or call (315) 400-2654.