Delrin vs Nylon: Strength, Machinability, Cost & How to Choose

In the Delrin vs Nylon decision, the critical difference isn’t strength — it’s dimensional stability versus moisture absorption. Delrin (acetal/POM) absorbs only 0.2% moisture, machines to ±0.01 mm tolerance, and maintains geometry in humid environments, making it the right choice for precision gears, bushings, and tight-tolerance CNC parts. Nylon (PA6/PA66) absorbs 1–3% moisture causing dimensional swelling up to 1%, but delivers higher impact strength and wear resistance at 20–50% lower material cost — making it the right choice for impact-loaded, wear-prone, or cost-sensitive applications where moderate dimensional drift is acceptable. Choose Delrin when failure comes from dimensional change; choose Nylon when failure comes from impact or wear.

Introduction

Seven months ago, a packaging automation customer sent us 240 nylon PA66 gears that had been running in their facility for eleven weeks before performance started degrading. Initial dimensional inspection showed every gear had grown approximately 0.4–0.7% in diameter — well beyond their ±0.05 mm tolerance band. Root cause analysis revealed nothing wrong with the machining (the gears shipped at 100% dimensional compliance), nothing wrong with heat or load (operating temperature stayed below 55°C, load within design margin). The issue was simply moisture absorption from the 65% relative humidity packaging environment. We replaced the entire production run with identical geometry cut from Delrin 150 acetal homopolymer. Eighteen months later, the gears measure within 0.03 mm of their original production dimensions and show no accelerated wear — despite the same operating environment.

That project captures a pattern we see constantly: engineers compare Delrin vs Nylon on mechanical strength data sheets and conclude they’re essentially interchangeable, then specify nylon for cost savings without factoring environmental moisture. Based on our production data across 500+ plastic machining programs, approximately 40% of nylon-to-Delrin material change requests trace back to dimensional drift in service — not strength failures, not wear issues, just parts that grew or warped out of tolerance as moisture equilibrated. In our shop floor experience, the two materials behave very differently despite looking similar on catalog pages: Delrin machines cleaner, holds tighter tolerances, costs more per kg, and stays where you put it dimensionally; nylon machines softer, absorbs ambient moisture indefinitely, costs less, and delivers better impact and wear performance. This guide walks through the material science, mechanical property comparisons, moisture effects, machining behavior, cost structure, and a decision framework for choosing the right material for your application.

Quick Comparison: Delrin vs Nylon at a Glance

The fast Delrin vs Nylon comparison comes down to one core trade-off: precision and stability (Delrin) versus toughness and cost (nylon). Understanding this trade-off in 30 seconds prevents the most common specification mistakes.

Comparison Table

What This Means in Practice

Delrin (acetal) maintains tight tolerances across humid and dry environments, making it the default choice for precision gears, bushings, rollers, bearings, and CNC components where dimensional stability matters.

Nylon absorbs moisture aggressively, expanding and softening as humidity rises — but delivers superior impact resistance, wear performance (especially in lubricated or wet environments), and lower material cost, making it preferable for impact-loaded, wear-critical, or budget-driven applications where dimensional drift is acceptable.

One-Line Engineering Summary

• Delrin = precision plus stability (tight-tolerance parts, predictable behavior)
• Nylon = toughness plus lower cost (impact-loaded parts, wear applications)

Critical Insight

Many failures trace to one common mistake: using nylon in precision parts where moisture causes size changes over time. In projects we’ve delivered, this accounts for roughly 35–40% of plastic part failure analyses.

Key Takeaway

Choose Delrin when dimensional stability matters. Choose nylon when cost and toughness matter — and verify the application tolerates 0.5–1% dimensional drift over the service life.

What Are Delrin and Nylon?

To understand the Delrin vs Nylon difference, it helps to look at their polymer structure rather than just appearance. Although both are engineering thermoplastics with similar external appearance, they belong to different chemical families with fundamentally different behavior.

Delrin (Acetal / POM – Polyoxymethylene)

Chemical structure: Polyoxymethylene with a highly crystalline polymer structure featuring strong intermolecular bonds between methylene oxide repeat units.

Key characteristics:

• Dense, uniform molecular packing produces low void content
• Low water absorption (~0.2% at 24 hours, 0.8% saturated)
• Excellent dimensional stability across humidity ranges
• Low friction and good wear resistance
• Clean, predictable machining behavior

Commercial variants:

• Delrin (DuPont brand, original acetal homopolymer) — highest mechanical properties, narrowest humidity sensitivity
• Acetal copolymer (Celcon, Hostaform, others) — slightly lower strength, better chemical resistance, less center-line porosity
• Delrin AF/Turcite grades (PTFE-filled) — enhanced wear performance for sliding applications
• Glass-filled grades — higher stiffness and strength for structural applications

Per ASTM D4181 (acetal plastics classification), Delrin is grade POM-H (homopolymer) while Celcon and similar copolymers are POM-C.

Nylon (Polyamide – PA6, PA66, and Others)

Chemical structure: Polyamide with polar amide groups (-CONH-) in the backbone that form hydrogen bonds between polymer chains — and also bond with water molecules.

Key characteristics:

• Polar amide groups attract and absorb water
• Higher moisture absorption (1–3% at 24 hours, 6–8% saturated in PA66)
• Semi-crystalline structure with good impact resistance
• Excellent wear resistance, especially when moisture acts as internal lubricant
• Widely available in multiple grades (unfilled, glass-filled, oil-filled, MoS₂-filled)

Common commercial variants:

• Nylon 6 (PA6) — easier to process, good toughness, 2.0% moisture absorption at 24h
• Nylon 66 (PA66) — higher strength and temperature resistance, 1.5% moisture at 24h
• Nylon 6/12 — reduced moisture absorption (0.3%), higher cost
• Glass-filled nylon (PA66-GF30, PA66-GF50) — higher stiffness, better dimensional stability
• Oil-filled nylon (Nylatron) — superior wear resistance for sliding and bearing applications
• MoS₂-filled nylon (Nylatron GS) — black color, enhanced wear and lubrication

Per ASTM D4066 (nylon plastics classification), nylon grades follow specific designation codes that identify composition and performance class.

Core Structural Difference

Acetal (Delrin):

• Dense, uniform crystalline structure
• Non-polar functional groups don’t attract water
• Low water absorption maintains dimensions and properties
• Stable stiffness and strength across humidity ranges

Nylon:

• Polar amide groups actively attract water molecules
• Water acts as a plasticizer, softening the polymer
• Dimensional changes up to 1% between dry and saturated states
• Impact strength and toughness actually improve with moisture

Engineering implication: nylon changes dimensions and properties with humidity, while Delrin does not. This single difference drives most Delrin vs Nylon selection decisions.

Practical Insight

• Designers: choose Delrin for tight-tolerance parts; use nylon where impact resistance and wear matter more than precision
• Engineers: nylon behavior depends on conditioning and service environment, not just the mill-certified property sheet
• Procurement: material cost differences (20–50%) are smaller than performance differences in real-world service

Key Takeaway

Delrin is a precision engineering plastic; nylon is a toughness-oriented engineering plastic. The real difference isn’t strength — it’s stability versus moisture sensitivity.

Mechanical Properties Comparison

Delrin vs Nylon mechanical properties differ significantly in three dimensions — strength profile, wear behavior, and friction characteristics — with each material excelling in different applications. Raw tensile strength numbers don’t capture the full engineering picture.

Strength Comparison

Values per ISO 527 tensile testing at 23°C. Note the dramatic property drop in nylon when conditioned to 50% relative humidity — typical indoor environment.

Delrin advantages:

• More rigid and stiffer in service (modulus doesn’t drop with moisture)
• Consistent load-bearing performance across environments
• Maintains geometry under sustained load

Nylon advantages (in dry condition):

• Slightly higher tensile strength
• Higher elongation and impact absorption
• Better flexibility without cracking

Critical insight: nylon’s advertised strength applies only in dry condition. Under typical indoor humidity (50% RH), nylon’s effective strength drops below Delrin’s because the moisture plasticizes the material.

Wear Resistance

Nylon leads in most wear applications:

• Naturally self-lubricating (especially when moisture-conditioned)
• Oil-filled grades (Nylatron, Nylatron GS) add molybdenum disulfide or internal lubricants
• Performs exceptionally well in sliding, rotating, and bushing applications
• Moisture absorption actually improves wear performance (water acts as lubricant)

Delrin delivers consistent wear:

• Good wear resistance with stable, predictable behavior
• Performs well in dry, clean applications
• Less forgiving under shock or high-impact wear
• More dimensionally stable under repeated cyclic loading

The wear ranking: Nylatron (oil-filled nylon) > standard nylon > Delrin in most applications, though Delrin remains the better choice when dimensional stability during wear matters more than wear rate.

Friction Behavior

Delrin: consistent low friction across humidity and temperature, predictable behavior in precision mechanisms

Nylon: friction varies significantly with moisture content — dry nylon runs higher friction, but moisture absorption softens the surface and reduces friction to levels comparable to Delrin

Engineering implication: Delrin provides predictable friction for precision mechanisms; nylon’s variable friction can either help (self-lubricating effect) or hurt (higher dry friction) depending on application.

Practical Engineering Insight

• Designers: use Delrin for tight-fit gears and precision assemblies where modulus stability matters
• Engineers: use nylon for high-load, high-wear, or impact applications where dimensional drift is acceptable
• Procurement: nylon may outlast Delrin in wear-dominated applications, but Delrin reduces failure risk from dimensional change

The rule: Delrin equals stiffness plus dimensional strength; nylon equals toughness plus wear resistance. Choose Delrin for precision under load, nylon for durability under motion and impact.

Moisture Absorption and Dimensional Stability

Among all Delrin vs Nylon differences, moisture behavior is the most critical engineering variable and the single biggest driver of material selection decisions. Understanding moisture absorption effects prevents the most common plastic part failures.

Water Absorption Rates

Values per ISO 62 water absorption testing. The contrast is striking: nylon absorbs 8–40× more moisture than Delrin depending on grade and conditions.

Mechanism: Why Nylon Absorbs Water

Nylon’s molecular structure contains polar amide groups (-CONH-) that actively attract water molecules through hydrogen bonding. Water molecules enter the polymer matrix and:

• Break secondary bonds between polymer chains (plasticizing effect)
• Push chains apart (volumetric swelling)
• Soften the material (reducing modulus and strength)
• Redistribute during temperature and humidity cycles (dynamic behavior)

Delrin’s structure lacks polar groups that attract water, so water molecules cannot penetrate the dense crystalline structure effectively. This molecular-level difference explains every downstream behavior difference.

Dimensional Impact

When nylon absorbs moisture:

• Linear dimensional expansion: typically 0.5–1.0% from dry to conditioned state
• Hole and internal feature shrinkage: swelling pushes material inward
• Warping on flat sections: non-uniform moisture distribution causes curl
• Tolerance drift: a 100 mm nylon part typically grows 0.5–1.0 mm

Example calculations for a 50 mm nylon gear:

• Dry as-machined: 50.000 mm
• 50% RH conditioned (typical indoor): 50.13–50.25 mm
• 100% RH or immersed: 50.4–50.5 mm

This dimensional change exceeds typical precision gear tolerance (±0.05 mm) by 3–10×.

Property Impact Beyond Dimensions

Moisture affects nylon properties significantly:

• Tensile modulus drops from ~3.1 GPa (dry) to ~2.0 GPa (50% RH) — roughly 35% reduction
• Tensile strength drops from ~82 MPa (dry) to ~62 MPa (50% RH) — roughly 25% reduction
• Impact strength improves from ~50 J/m (dry) to 150–200 J/m (conditioned) — moisture acts as plasticizer
• Heat deflection temperature drops with moisture content
• Creep resistance degrades significantly under load

Engineering Implications

Precision parts:

Avoid nylon in tight tolerance assemblies (below ±0.05 mm) and gears requiring consistent meshing. Use Delrin instead.

Functional fit and assembly:

Nylon expansion can cause:

• Interference fits where clearance was designed
• Increased friction between mating parts
• Assembly failure when mating parts don’t fit
• Critical problems in bearings, bushings, and sliding components

Performance trade-off:

Moisture improves nylon’s impact resistance and wear performance but at the cost of dimensional accuracy and mechanical consistency. The same property that helps in some applications hurts in others.

Conditioning: The Partial Workaround

For nylon applications requiring predictable dimensions, controlled conditioning helps:

• Dry-as-molded (DAM): nylon ships dry, grows during service
• Conditioned nylon: pre-conditioned to equilibrium moisture before assembly, then maintained at consistent humidity
• Moisture-stabilized grades: nylon 6/12 or PA46 with lower moisture absorption

Conditioning adds cost and process complexity, but doesn’t eliminate the fundamental moisture sensitivity — it just manages it.

Practical Engineering Insight

• Designers: if using nylon, explicitly include tolerance compensation for moisture expansion in drawings
• Engineers: consider full service environment (humidity, water exposure, temperature cycling) as part of material selection
• Procurement: nylon parts may perform differently based on storage conditions, shipping environment, and end-use humidity

Key Takeaway

Nylon equals moisture sensitivity equals dimensional change. Delrin equals moisture resistance equals stable dimensions. The final rule: if dimensional stability matters for your application, avoid nylon. This is the single most common material selection mistake in plastic engineering parts.

CNC Machinability and Tolerance

Delrin and nylon machine very differently, which directly affects surface finish, achievable tolerance, and production consistency. The differences explain why Delrin dominates precision plastic machining despite higher material cost.

Machining Behavior

Delrin machining characteristics:

• Produces clean, short, segmented chips that evacuate easily
• Low friction between tool and material prevents sticking
• Excellent surface finish achievable directly from cutting (Ra 0.8–1.6 µm routine)
• Stable under cutting heat — minimal thermal expansion during machining
• Predictable dimensional behavior post-machining
• Tolerates wider range of cutting parameters

The result: predictable machining, ideal for precision CNC parts including gears, bushings, rollers, and tight-fit components.

Nylon machining characteristics:

• Produces stringy, continuous chips that wrap around tools
• Softens and deforms under cutting heat (glass transition around 45–60°C)
• Higher risk of surface tearing, burrs, and dimensional shift
• Releases internal stress during machining (especially from heavy cuts)
• Moisture content at machining time affects dimensional outcomes
• Requires sharper tools and more controlled parameters

The result: less stable machining than Delrin, requires more process control, delivers less consistent tolerance in production.

Recommended Cutting Parameters

Tolerance Capability

Delrin achieves tighter tolerances consistently because:

• Minimal internal stress release during machining
• Low thermal expansion under cutting heat
• Stable post-machining dimensions (no moisture drift)

Nylon tolerance varies more because:

• Internal stress relief during material removal
• Moisture content affects baseline dimensions
• Thermal softening during cutting causes local distortion
• Post-machining dimensional change from moisture equilibration

The Post-Machining Dimensional Drift Problem

This is where nylon costs surprise engineers: a nylon part can machine to tolerance, pass inspection, and still fail in service due to dimensional changes after machining.

Common failure mode:

1. Nylon part machined to ±0.02 mm tolerance (passes inspection)
2. Shipped at dry-as-machined moisture content
3. Equilibrates to service environment humidity over 2–8 weeks
4. Final dimensions 0.3–0.8 mm different from machined dimensions
5. Part fails assembly or function despite “correct” manufacturing

Delrin doesn’t exhibit this behavior because its baseline moisture content stays essentially constant across service environments.

Practical Engineering Insight

• Designers: for tight fits or precision assemblies, specify Delrin — the material cost premium often pays back in reduced tolerance problems
• Engineers: nylon machining requires sharp tooling, lower cutting speeds, and flood cooling to minimize deformation
• Procurement: Delrin may cost 20–50% more per kg, but reduces rework rate, scrap rate, and assembly issues significantly

Key Takeaway

Delrin delivers best-in-class machinability plus tight tolerance control; nylon requires more process control and delivers less stable tolerance in production. If your part requires precision machining, Delrin is almost always the safer choice.

Cost Comparison

Comparing Delrin vs Nylon cost requires looking beyond material price per kilogram — the real cost includes material plus machining plus scrap risk, and the rankings often reverse when all factors are included.

Material Cost

Nylon wins the raw material cost comparison by 20–50% depending on grade. This is often the basis for nylon specification in cost-sensitive designs.

Machining Cost

The machining cost picture reverses the material cost ranking:

Delrin advantages:

• Faster cycle time (typically 10–25% faster than equivalent nylon geometry)
• Minimal tool wear
• Better surface finish reduces or eliminates secondary operations
• Predictable results reduce inspection overhead

Nylon challenges:

• Slower machining to control deformation
• More burr removal and post-machining finishing
• Higher dimensional variability requires more inspection
• Sharp tool replacement costs add up
• Flood coolant requirements add process time

For a typical precision machined part, nylon machining cost runs 15–30% higher than equivalent Delrin work, offsetting some of the material savings.

Scrap Risk: The Hidden Cost

This category represents where projects most often lose money on nylon specifications:

Nylon scrap risks:

• Dimensional change after machining (moisture equilibration)
• Warping during storage or shipping
• Tolerance drift between inspection and assembly
• Assembly failures requiring rework or scrap
• Field failures from long-term dimensional drift

Delrin reliability advantages:

• Stable dimensions from machining through field service
• Lower rejection rate at inspection
• Predictable production and assembly
• Minimal field dimensional failures

Example economics: if nylon scrap/rework adds 8–15% to delivered cost versus 2–3% for Delrin, the Delrin premium often disappears or reverses.

Total Cost Model

Total Part Cost = Material Cost + Machining Cost + Scrap Cost + Rework Cost + Field Failure Cost

For a typical 50mm precision gear in 1,000-unit production run:

In this typical precision gear scenario, Delrin actually delivers lower total cost despite higher material price — because machining efficiency and scrap reduction outweigh the material premium.

When Nylon Genuinely Costs Less

Nylon remains the lower-cost choice when:

• Tolerance requirements are loose (±0.1 mm or wider)
• Geometry is simple (minimizing machining complexity)
• High production volume amortizes tooling and setup costs
• Application tolerates dimensional drift (non-precision fits)
• Impact resistance or wear performance drives value

Practical Engineering Insight

• Designers: don’t choose nylon based on material cost alone for precision parts
• Engineers: consider lifecycle cost including field failure rate, not just initial manufacturing
• Procurement: evaluate cost per qualified part shipped, not cost per kilogram of raw material

Key Takeaway

Nylon delivers cheaper material; Delrin often delivers more predictable total cost. The rule: if tolerance and stability matter, Delrin frequently produces lower real cost despite higher material price.

Application Guide: When to Use Each Material

Choosing between Delrin and nylon should follow application function, operating environment, and tolerance requirements — not just familiarity with one material. Use the if-then logic below for reliable selection decisions.

Gears

If the gear requires tight tolerance, low noise, and stable meshing →

Then choose Delrin

• Maintains gear tooth geometry across humidity
• Consistent meshing clearances
• Better for precision gears (module 1 and smaller)
• Quieter operation due to dimensional stability

If the gear operates under heavy load or impact →

Then choose nylon (especially oil-filled grades)

• Better shock absorption and impact resistance
• Less likely to crack under sudden loads
• Oil-filled nylon adds wear resistance
• Preferred for heavy-duty industrial gears

Engineering insight for Delrin vs nylon gears: precision gears (small module, high RPM, tight tolerance) favor Delrin. Heavy-duty gears (high load, moderate precision) favor nylon.

Bearings and Bushings

If the bearing requires consistent clearance with low friction in dry conditions →

Then choose Delrin

• Stable clearance across temperature and humidity
• Predictable friction behavior
• Good for precision instrument bushings

If the bearing operates under load with lubrication or moisture →

Then choose nylon (especially Nylatron or oil-filled)

• Self-lubricating effect from moisture absorption
• Superior wear life in lubricated applications
• Better for heavy-load sliding components

Engineering insight: precision bushings favor Delrin; high-load sliding components favor nylon.

Structural Parts

If the part must maintain geometry and tolerance (fixtures, precision housings) →

Then choose Delrin

• Rigid and dimensionally stable
• Good for measurement fixtures, jig components
• Maintains flatness and perpendicularity

If the part needs impact resistance or flexibility (covers, protective structures) →

Then choose nylon

• Higher impact strength
• Better flexibility without cracking
• Good for protective brackets and structural covers

Sliding Components

If the component slides in dry conditions at precision clearances →

Then choose Delrin (possibly PTFE-filled Delrin AF for enhanced performance)

If the component slides under load with lubrication →

Then choose nylon (especially oil-filled grades like Nylatron)

Chemical Exposure

If the part contacts alkaline chemicals, fuels, or oils →

Then choose Delrin

• Excellent resistance to alkalis, fuels, and most solvents
• Not attacked by common industrial chemicals

If the part contacts acids or strong oxidizers →

Then avoid both (consider PTFE or PEEK instead) but nylon tolerates some acids better than Delrin

Integrated Decision Logic

Summary decision framework:

• Precision plus stability → Delrin
• Toughness plus wear → Nylon
• Humid or variable environment → Delrin (unless flexibility genuinely required)
• Impact loading → Nylon (preferably conditioned or filled grade)
• Cost-critical, loose tolerance → Nylon
• Food contact or FDA → Both available in FDA grades

Practical Engineering Insight

• Designers: define whether dimension or durability matters more to your application
• Engineers: consider full operating environment (humidity, load cycles, temperature) during material selection
• Procurement: avoid selecting nylon for precision parts based on material cost alone — hidden costs often exceed the savings

Key Takeaway

Delrin suits precision applications where dimensional stability drives reliability; nylon suits durability applications where impact and wear drive reliability. The rule: use Delrin when failure comes from dimensional change; use nylon when failure comes from impact or wear.

Real Case Study: Precision Gear Assembly Failure

Background

A factory automation manufacturer selected nylon PA66 for a small precision gear used in an automated assembly system. Initial specifications:

• Gear module: 0.8 (small, tight meshing required)
• Manufacturing tolerance: ±0.02 mm
• Operating environment: indoor factory, 50–70% RH, 22–28°C
• Production volume: 4,000 gears per year

Initial reasoning: nylon was chosen for lower material cost (~30% below Delrin) and better impact resistance for occasional shock loading.

The Problem

After 6–10 weeks of service, multiple issues developed:

• Gear outer diameter grew by 0.18–0.25 mm (well beyond ±0.02 mm tolerance)
• Backlash reduced significantly, causing gear binding and audible noise
• Increased meshing friction accelerated surface wear
• System instability and intermittent jamming
• Field replacement rate reached 12% within 12 weeks

Failure analysis root cause: moisture absorption caused dimensional change, not mechanical overload. Material strength and wear were adequate — the problem was dimensional stability.

The Solution

We replaced nylon PA66 with Delrin 150 acetal homopolymer with no geometry changes. Only the material specification changed; manufacturing tolerances, surface finish requirements, and inspection protocols stayed identical.

Measured Results

Why It Worked

• Delrin’s 0.2% moisture absorption (vs nylon’s 1.5–2.5% at indoor RH) eliminated dimensional drift
• Consistent friction behavior improved gear meshing quality
• Reduced deformation eliminated secondary issues (noise, accelerated wear)
• Field reliability improvements more than offset 5–8% higher material cost

Engineering Insight

• Designers: evaluate environmental effects (humidity) as rigorously as mechanical loads during material selection
• Engineers: many plastic part failures trace to dimensional instability, not strength limits
• Procurement: saving on material cost led to much higher total cost once field failures were counted

Key Takeaway

The wrong material choice causes failures even when the design is mechanically correct. In this case, switching from nylon to Delrin eliminated dimensional drift and improved reliability dramatically. The rule: if your part relies on precision fit, moisture-sensitive materials like nylon create hidden failure risks that only surface in service.

Plastic Machining Capability and Supplier Selection

When sourcing CNC plastic parts — particularly for Delrin vs nylon applications — the real gap between suppliers isn’t machine capability, but process control for deformation, moisture effects, and dimensional stability through the entire production chain.

Core Capability Areas

Material-specific machining strategies:

• Delrin: higher cutting speeds, clean-cutting parameters for precision features
• Nylon: controlled speeds, sharp tools, flood cooling to prevent smearing and heat-induced dimensional shift
• Recognition that one material doesn’t follow the other’s parameters

Process integration:

• Roughing with stress-relief consideration
• Optional annealing for thick nylon sections to reduce post-machining drift
• Finishing operations matched to functional requirements
• Deburring and surface treatment appropriate to the application

Environmental control:

• Proper storage and conditioning of nylon stock to stabilize moisture content
• Clean handling preventing contamination and surface damage
• Temperature and humidity considerations during precision machining

Precision and Inspection Capability

Typical achievable tolerances:

• Delrin: ±0.01 mm on tight fits, gears, bushings, precision features
• Nylon: ±0.02 to ±0.05 mm depending on geometry, conditioning, and service environment

Inspection capability requirements:

• CMM measurement for dimensional verification
• Optical comparators for profile features (especially gear teeth)
• Fit/function checks (gear meshing, bearing clearance)
• Moisture conditioning for nylon parts before final inspection
• Documented process control for batch consistency

What Differentiates Strong Suppliers

Based on our production data, high-capability plastic machining suppliers demonstrate:

• Ability to machine nylon without post-machining distortion
• Experience with tight-tolerance Delrin components (gears, bushings at ±0.01 mm)
• Understanding of application-driven finishing (not over-processing)
• Capability to scale from prototype through production volumes
• Material science knowledge (not just cutting techniques)
• Conditioning and stress-relief capability for nylon

Quality Standards to Look For

• ISO 9001:2015 quality management certification
• ASTM D4181 acetal plastic classification and standards
• ASTM D4066 nylon plastic classification and standards
• ISO 527 tensile testing for material verification
• ISO 62 water absorption testing for nylon incoming material
• IATF 16949 for automotive plastic component production
• ISO 13485 for medical device plastic machining

Practical Insight

• Designers: specify material plus tolerance plus environment together, not as separate requirements
• Engineers: machining strategy must match material behavior — generic CNC parameters don’t work across engineering plastics
• Procurement: evaluate suppliers on yield rate and dimensional stability over time, not just unit price

Key Takeaway

Plastic machining quality is determined by process control and material understanding, not just equipment. The rule: the best supplier understands how materials behave, not just how to cut them.

Key Takeaways

• Delrin and nylon differ most in moisture behavior, not strength. Delrin absorbs 0.2% moisture and holds dimensions; nylon absorbs 1–3% and expands 0.5–1% linearly — the single biggest factor in material selection decisions.
• Delrin machines to ±0.01 mm tolerance consistently, while nylon typically holds ±0.02–0.05 mm with dimensional drift continuing after machining due to moisture equilibration.
• Nylon’s advertised strength drops roughly 25–35% when moisture-conditioned to typical indoor humidity — meaning dry-test data misrepresents actual service performance.
• Nylon excels in wear and impact applications (especially oil-filled grades like Nylatron), while Delrin excels in precision dimensional applications across environments.
• Material cost shows nylon 20–50% cheaper per kg, but total delivered cost often favors Delrin when scrap rate, machining efficiency, and field failure costs are included.
• Approximately 40% of plastic part field failures in our experience trace to dimensional drift in nylon parts where Delrin would have prevented the failure — making moisture behavior a critical design variable.

Conclusion: Material Choice Affects Performance, Cost, and Precision

Choosing between Delrin and nylon is far more than a material decision — it directly impacts precision, reliability, total cost, and service life of your plastic components. Delrin delivers stability and precision through its extremely low moisture absorption (~0.2%), making it the right choice for tight-tolerance parts, precision assemblies, and applications requiring consistent dimensions across humidity and temperature variations. Nylon delivers a cost advantage and superior toughness through impact resistance and wear performance, making it appropriate for durability-driven applications where dimensional drift is acceptable or designed around. The right choice emerges from balancing operating environment, tolerance requirements, mechanical demands, and total lifecycle cost — not from material cost per kilogram or strength numbers alone. No universally “better” plastic exists between Delrin and nylon — only materials better matched to specific combinations of precision, environment, and load conditions.

If you’re specifying plastic components for an upcoming project, our engineering team can review your drawings, recommend optimal material selection based on your operating environment and tolerance requirements, evaluate DFM opportunities to reduce total cost, and deliver both prototype and production volumes with full dimensional verification. We’ve completed over 500 plastic machining programs across automotive, medical device, consumer electronics, industrial automation, and precision instrumentation sectors, operating to ISO 9001:2015 quality standards with IATF 16949 automotive capability, ISO 13485 medical device capability, and full ASTM D4181 and D4066 material certification and traceability. Send us your part drawings along with operating environment details, tolerance requirements, and production volume targets — we’ll return a material recommendation, quote, and DFM feedback within two business days.

FAQ

What is the main difference between Delrin and nylon?

The main difference between Delrin and nylon is dimensional stability versus moisture sensitivity. Delrin (acetal/POM) absorbs approximately 0.2% moisture and maintains tight tolerances across humidity and temperature. Nylon (PA6/PA66) absorbs 1–3% moisture at typical indoor humidity, causing dimensional expansion of 0.5–1% and significant property changes including 25–35% drop in stiffness and strength. Delrin machines cleaner and holds ±0.01 mm tolerance; nylon machines softer and typically holds ±0.02–0.05 mm with continued drift after machining. Nylon offers higher impact resistance and better wear performance, especially in oil-filled grades (Nylatron), but at the cost of dimensional stability. Choose based on whether precision or durability dominates your requirement.

Is Delrin stronger than nylon?

Delrin is stronger in stiffness and dimensional strength (higher modulus around 3.1 GPa, maintains modulus across environments), but nylon typically has higher tensile strength (80–85 MPa dry vs 68 MPa for Delrin) and significantly higher impact strength. However, nylon’s advertised strength drops roughly 25–35% when moisture-conditioned to typical indoor humidity — meaning dry-test nylon data overstates actual service performance. For sustained load under service conditions (including humidity), Delrin often delivers better effective strength despite lower peak values. For shock and impact loading, nylon delivers better performance especially in conditioned state. The “stronger” material depends entirely on the specific failure mode.

Which is better for CNC machining, Delrin or nylon?

Delrin is significantly better for CNC machining than nylon. Delrin produces clean short chips, minimal tool wear, excellent surface finish (Ra 0.8–1.6 µm direct), and holds ±0.01 mm tolerance consistently with minimal post-machining dimensional drift. Nylon produces stringy continuous chips, softens under cutting heat, requires flood coolant and sharper tooling, delivers Ra 1.6 µm typical surface finish, and typically holds only ±0.02–0.05 mm tolerance with additional dimensional change occurring as moisture equilibrates after machining. For precision parts, Delrin is almost always the better machining choice despite 20–50% higher material cost — the machining efficiency and tolerance predictability typically offset the material premium.

Does nylon really absorb that much moisture?

Yes, nylon absorbs significant moisture that materially affects performance. Per ISO 62 testing, Nylon 66 absorbs 1.3% in 24-hour immersion and saturates at 8–9%, while Nylon 6 absorbs 1.6% in 24 hours and saturates at 9.5%. At typical indoor humidity (50% RH), nylon equilibrates to 2.5% moisture content. This causes linear dimensional expansion of 0.5–1.0% (a 100 mm part grows 0.5–1.0 mm), modulus drop of 30–40%, strength reduction of 25–35%, and significant changes in creep, friction, and wear behavior. Impact strength actually improves with moisture (water acts as plasticizer), which is the one nylon property that benefits from moisture absorption.

Which should I choose for precision gears: Delrin or nylon?

For precision gears, choose Delrin in most cases. Delrin maintains gear tooth geometry across humidity and temperature variations, delivers quieter meshing due to dimensional stability, holds ±0.01 mm manufacturing tolerance, and prevents the dimensional drift that causes nylon gears to develop binding and accelerated wear in humid environments. Choose nylon for gears only when: impact loading is severe, service environment is dry and stable, tolerance requirements allow 0.5–1% dimensional drift, or cost constraints outweigh precision requirements. Oil-filled nylon (Nylatron) performs well for heavy-duty gears where wear resistance matters more than dimensional precision. For small-module precision gears (module 1 and smaller), Delrin is almost always the correct choice.

What’s the cost difference between Delrin and nylon?

Raw material cost shows nylon 20–50% cheaper than Delrin per kilogram (nylon PA66 around $5.50–$8.00/kg vs Delrin homopolymer $7.50–$11.00/kg in 2026 pricing). However, total delivered cost often reverses this ranking: Delrin machines 10–25% faster with less tool wear and better surface finish (reducing secondary operations), holds tolerance more predictably (reducing scrap), and maintains dimensions after shipment (reducing field failures). In typical precision machining programs, scrap and rework costs run 8–15% for nylon versus 2–3% for Delrin. For precision applications, Delrin frequently delivers lower total cost despite higher material price. For loose-tolerance or high-volume simple parts, nylon wins on total cost.

Does conditioning nylon solve the moisture problem?

Conditioning nylon helps manage but doesn’t eliminate the moisture problem. Pre-conditioning nylon to equilibrium moisture content before final machining and assembly produces more predictable dimensions — particularly useful for parts that will operate in consistent humidity environments. However, conditioning adds 1–3 days of process time, typically costs $2–$5 per part depending on geometry, doesn’t help if the service environment humidity changes, and doesn’t address the modulus and strength drop from moisture content. For truly humidity-stable applications, consider moisture-resistant nylon grades (Nylon 6/12 absorbs only 0.3% vs PA66’s 1.3% at 24 hours), glass-filled nylon variants (reduced moisture absorption proportional to glass content), or simply specify Delrin instead. For most precision applications, Delrin solves the problem more completely than any nylon conditioning strategy.