Nylon CNC Machining — Properties and Grades
Nylon (polyamide, PA) is one of the most versatile engineering thermoplastics. It is tougher than Delrin at impact, bonds well to adhesives and coatings, and PA66 glass-filled grades offer useful stiffness at elevated temperatures. The tradeoff is higher moisture absorption than acetal — nylon absorbs 2–8% moisture depending on grade, which causes dimensional swelling and slight reduction in stiffness. For most mechanical applications at room temperature, nylon and Delrin perform similarly; the right choice depends on the specific load, environment and temperature.
Nylon Grades We Machine
| Grade | Key property | Best for |
|---|---|---|
| PA6 (Nylon 6) | Cast, large blocks available; good toughness | Large bushings, wear pads, structural blocks |
| PA66 (Nylon 6/6) | Higher melting point, stiffer than PA6 | Gears, wear parts at elevated temperature |
| PA12 (Nylon 12) | Lowest moisture absorption in the nylon family | Precision parts, fuel system components, low-moisture environments |
| MDS-filled Nylon | Molybdenum disulfide filled — reduced friction | Bearings, bushings, gears (self-lubricating) |
| Glass-Filled Nylon (PA66-GF30) | 30% glass fibre — high stiffness, heat resistance | Structural load-bearing parts, elevated temperature |
Mechanical Properties (PA66 — dry as-machined)
| Property | PA66 (dry) | PA66-GF30 (dry) |
|---|---|---|
| Tensile strength | ~83 MPa | ~185 MPa |
| Flexural modulus | ~2.9 GPa | ~9.0 GPa |
| Max continuous service temp | ~105–120 °C | ~130–150 °C |
| Water absorption (equilibrium) | ~2.5–3% | ~1.5% |
| Density | 1.14 g/cm³ | 1.37 g/cm³ |
Note: nylon properties change significantly with moisture content — parts stabilise at ~2–3% moisture in normal ambient conditions, which reduces stiffness and strength from the "dry" values above. Design critical nylon parts for conditioned (ambient-exposed) properties.
How We Machine Nylon
- Tolerances: ±0.05 mm for moisture-critical features; ±0.025 mm achievable on features not subject to significant moisture variation.
- Tooling: Sharp uncoated carbide at high speeds; nylon has a tendency to melt and smear at the tool tip if feed is too light — keep positive cutting action at all times.
- Moisture conditioning: Parts destined for wet or outdoor service should be conditioned before final machining to avoid dimensional change in service.
- Glass-filled grades: PA66-GF30 is significantly more abrasive — carbide tooling required, tool life reduced versus unfilled nylon.
Typical Nylon CNC Parts
- Bearings and bushings — MDS-filled nylon for self-lubricating applications
- Gears for light loads — quieter than metal, self-lubricating; suitable for light-to-medium duty
- Cable guides and pulleys — smooth, durable surface for rope and cable
- Pipe fittings and flanges — PA12 for fuel/chemical compatibility
- Structural support blocks — cast PA6 blocks for machinery mounting
- Rollers and wear pads — conveyor, packaging machinery
- Replacement plastic parts — nylon components in legacy machinery reproduced from worn parts; see our replacement parts service
Nylon vs Delrin for CNC Machined Parts
| Nylon (PA66) | Delrin (POM-H) | |
|---|---|---|
| Tensile strength (dry) | ~83 MPa | ~68 MPa |
| Moisture absorption | ~2.5–3% (dimensional change) | ~0.25% (minimal) |
| Impact toughness | Higher | Good |
| Friction / wear | Good (MDS grade: excellent) | Very good |
| Dimensional stability | Lower in humid environments | Better |
| Best for | Gears, structural parts, high-impact | Precision bushings, valve parts, guides |
Default to Delrin/acetal for precision parts requiring dimensional stability in varying humidity. Use nylon when higher impact resistance, elevated temperature performance (GF30) or specific chemical compatibility (PA12) is needed.
Custom Nylon Parts — Who Orders and Why
Nylon buyers come to us for parts needing more impact resistance than Delrin, elevated temperature performance (glass-filled grades), or self-lubrication without added lubricant (MDS-filled). Common orders are gears, wear pads, bushings and legacy plastic machine parts.
"PA6 wear pads — custom profile, bolt holes to our pattern, 50 pcs"
Cast PA6 is ideal for large wear pads and structural blocks — available in large stock sizes and machines quickly. We machine custom cross-sections, counter-bore holes and chamfers to your drawing. 50 pcs in 2–3 weeks. PA6 wear pads are a recurring order for conveyor and packaging machinery suppliers.
"Replacing steel bushings in a corrosive environment — need nylon, exact dimensions required"
PA12 or MDS-filled PA66 are the standard choices for corrosive-environment bearing replacements. We machine to ±0.025 mm on bore and OD, accounting for expected moisture expansion in service. Send the existing steel bushing dimensions — we recommend the best grade based on temperature and fluid exposure.
"Nylon gear in old packaging machine — broken, no part number, worn sample only"
Send us the broken gear. We measure tooth profile, PCD, module, number of teeth, bore and keyway from the sample. We machine in PA66 or MDS-nylon (better wear), same geometry as the original. Old machinery plastic gears are a common reproduction request — no drawing required.
"GF30 nylon structural brackets — 150 °C continuous service, 25 pcs"
PA66-GF30 (30 % glass-filled) for structural parts at elevated temperature. We machine with carbide tooling (GF grades are abrasive) to your drawing. 25 pcs in 3 weeks. GF30 gives ~185 MPa tensile and 130–150 °C continuous service — significantly exceeding unfilled nylon.
What Nylon Parts Buyers Search For
Frequently Asked Questions
Yes. PA6 and PA66 absorb 2.5–3% moisture at equilibrium in ambient conditions, which causes ~0.5–1% linear dimensional change and reduces stiffness. For precision gears and tight-tolerance bearing bores, we machine to dimension after conditioning the stock at the expected ambient humidity. PA12 has the lowest moisture absorption of the nylon family (~0.7%) if dimensional stability is critical. Delrin (POM) is the first choice when moisture-driven dimensional change is unacceptable.
PA66 or MDS-filled PA66 for light-to-medium duty gears at up to ~120 °C. MDS (molybdenum disulfide) fills reduce the friction coefficient and improve wear life significantly. For higher loads or elevated temperatures, consider PA66-GF30 (glass-filled) for stiffness, or PEEK for extreme conditions. Nylon gears run quieter than metal and do not require lubrication in most applications.
Yes. Glass-filled nylon is significantly more abrasive than unfilled grades — we use carbide tooling and accept shorter tool life. The result is a stiffer, stronger part with better elevated-temperature performance. Specify the glass content and grade when enquiring.
Unfilled PA66: ~105–120 °C continuous. PA66-GF30: ~130–150 °C. PA12: ~100 °C. Above these ranges, nylon softens progressively. For higher temperatures (150–250 °C) consider PEEK, PEI, or PTFE. We advise on material selection when the service temperature is a critical parameter.
Yes. Nylon parts in old machinery — gears, bushings, guide rails, cam followers — are routinely reproduced from worn or broken samples. We measure the worn geometry, reconstruct dimensions, and machine new parts in the appropriate grade. If the original material grade is unknown, we recommend PA66 or MDS-nylon based on the application — both are likely to match or exceed the original performance.
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