You’ve designed a part for Delrin, but material costs are climbing or your supplier is having availability issues. With years of experience machining both materials for precision prototypes and production runs, we’ve seen many engineers successfully make this switch – but only when they understand the critical performance and manufacturing trade-offs.
UHMW can replace Delrin in many applications, but expect trade-offs in dimensional accuracy, surface finish, and wear resistance. UHMW excels in chemical resistance and impact strength but machines to looser tolerances than Delrin. Success depends on your specific performance requirements and acceptable tolerance ranges.
When material substitution works: scenarios, performance trade-offs, and design spec modifications for successful material switches in CNC machining.
Table of Contents
What's the Cost Difference Between Delrin and UHMW?
UHMW costs $6-8/lb vs Delrin’s $8-12/lb, but machining time increases 20-25%. For most parts over 100 pieces, UHMW saves 8-15% total cost. The break-even point is typically 75-150 parts depending on tolerance requirements and part geometry.
Here’s the real-world cost impact we see in our shop: A 2″ × 3″ bushing in UHMW costs $4.20 in material vs $6.80 for Delrin – saving $2.60 per part. However, machining time increases from 18 minutes to 23 minutes, adding $1.40 in labor at $60/hour shop rates. Net savings: $1.20 per part, or $120 for a 100-piece run.
The calculation changes dramatically with tighter tolerances. Parts requiring ±0.01 mm often need secondary operations with UHMW, including stress-relief cycles or finish boring. We recently quoted a medical housing where UHMW’s secondary operations added $8.50 per part – completely eliminating material savings. The customer stayed with Delrin.
Testing shows UHMW reduces carbide tool life by 25-30% due to its abrasive fillers. For 6mm end mills cutting UHMW, we replace tools every 15-20 hours vs 20-25 hours with Delrin. This adds approximately $0.20-0.35 per part in tooling costs on complex geometries.
Design Takeaway: Use this quick check – if your quantity × material savings per part > 150, consider UHMW. For parts needing ±0.01 mm tolerances or quantities under 75 pieces, stick
Immediate Cost Decision Tool
Your Part: _____ pieces needed
- Material savings: Approx $2-4 per part
- Added machining: +$1-2 per part
- Tool wear factor: +$0.20 per part
Quick Calculation: If (quantity × $1.50) > $150 = Consider UHMW If tolerances tighter than ±0.025 mm = Stay with Delrin
Which Material Holds Better CNC Machining Tolerances?
Delrin consistently achieves tighter tolerances than UHMW in our shop, typically holding ±0.01 mm on critical features while UHMW generally requires ±0.025 mm or looser due to material deflection and thermal expansion. UHMW has 12x the expansion rate of steel and is “incredibly hard to machine” for tight tolerance work, while Delrin’s rigidity supports precision machining with standard setups.
Quick Decision Rule: ✓ Assembly fits, threaded holes → Delrin only ✓ Standalone brackets, guides → Either works
✓ Non-critical covers, guards → UHMW saves cost
Delrin is “more suitable for parts that demand high dimensional accuracy and repeatability” compared to UHMW. Our CMM data shows medical device enclosures requiring ±0.005 mm wall thickness achieve 95%+ first-pass success in Delrin versus 70% in UHMW. Mating parts that must align during assembly consistently fail with UHMW due to deflection during cutting operations.
Threaded features present the biggest challenge. UHMW’s low melting point (270°F) and high thermal expansion cause material flow during tapping, especially in blind holes deeper than 2×diameter. Standard M6×1.0 threads in UHMW frequently fail gauge inspection, while Delrin maintains thread form consistently for reliable assemblies.
Surface finish follows tolerance capability, with standard CNC operations achieving Ra 3.2 μm “as machined”. Delrin achieves slightly better finishes for smooth mating surfaces, while UHMW’s fibrous structure produces rougher surfaces that work fine for non-critical applications.
Design Takeaway: Choose based on fit requirements. Delrin for parts that must assemble precisely or mate with other components. UHMW for standalone parts where dimensional variations won’t affect function and cost savings matter more.
Is Delrin or UHMW Better for High-Wear Applications?
UHMW dramatically outperforms Delrin in high-cycle sliding applications with superior abrasion resistance and self-lubricating properties. UHMW’s coefficient of friction (0.10-0.22) is lower than Delrin’s (0.2-0.35), and “UHMW in sliding applications will out wear steel 10 to 1”. The material excels specifically in contaminated, abrasive environments where Delrin would wear quickly.
Quick Decision Rule: ✓ Clean environment, low cycles → Either material works ✓ Dirty/abrasive environment, high cycles → UHMW strongly favored ✓ Food processing, chemical exposure → UHMW only
UHMW “excels in moist and abrasive environments, while Delrin performs better in dry conditions”. Testing confirms dramatic differences in contaminated applications – wear strips in packaging equipment with metal debris show UHMW lasting 18+ months versus Delrin’s 4-6 months. The material’s molecular structure resists cutting and tearing under sliding contact.
Chemical exposure amplifies UHMW’s advantages. Food processing conveyors exposed to cleaning chemicals and moisture benefit from UHMW’s resistance to swelling and degradation. UHMW shows “outstanding self-lubrication and excellent sliding abilities” that eliminate the need for external lubricants in wet environments.
Impact resistance sets UHMW apart for shock-loading applications. UHMW shows “impressive resistance to breakage from impacts, even during extremely cold temperatures”, making it ideal for chute liners and material handling equipment where sudden loads occur regularly.
Design Takeaway: Choose UHMW for harsh service conditions – contaminated environments, chemical exposure, high-impact applications. Reserve Delrin for clean, controlled environments where its better machinability and dimensional stability provide more value than extended wear life.
Which Has Better Impact Resistance: Delrin or UHMW?
UHMW delivers superior impact resistance with exceptional energy absorption, particularly in cold environments where Delrin becomes brittle. UHMW maintains performance “without degradation at extremely low temperatures (-452 degrees F)” and shows “impressive resistance to breakage from impacts, even during extremely cold temperatures. However, UHMW’s softness means it permanently deforms under concentrated loads.
Quick Decision Rule: ✓ Drop protection, shock absorption → UHMW ✓ Structural loads, point loads → Delrin ✓ Operating below 0°C → UHMW only ✓ Budget critical + short service → Either works
Our testing shows this difference in protective equipment applications. UHMW dock bumpers absorb forklift impacts effectively for 18+ months but develop 2-3mm permanent indentations at contact points. Delrin bumpers maintain their profile but crack after 8-12 months of similar impacts.
Red Flag Warning: Never use Delrin for impact applications below -10°C. We’ve seen brittle failures in cold storage facilities where Delrin conveyor guides shattered during normal operation.
Wall thickness affects performance differently. UHMW requires minimum 6mm thickness for effective impact absorption – thinner sections may tear rather than absorb energy. Delrin maintains consistent impact resistance across wall thicknesses but with lower absolute energy absorption.
Emergency Substitution: If UHMW unavailable, Delrin works for indoor applications above 10°C but expect 50% shorter service life in high-impact environments.
Design Takeaway: Choose UHMW when energy absorption matters more than maintaining shape – protective equipment, bumpers, cold environments. Select Delrin when you need impact resistance without permanent deformation.
Which Material Offers Superior Chemical Resistance?
UHMW provides broader chemical resistance than Delrin, with zero water absorption and excellent resistance to most industrial chemicals except hydrocarbons. UHMW handles “water solutions generally safe except highly oxidizing chemicals” but “hydrocarbons such as gasoline, kerosene, oil and grease cause swelling”. This makes material selection dependent on your specific chemical environment.
Quick Decision Rule: ✓ Food processing, cleaning chemicals → UHMW ✓ Fuel systems, oil exposure → Delrin ✓ Outdoor UV exposure → UHMW strongly favored ✓ Mixed environment (oil + cleaning) → Evaluate case-by-case
UHMW shows “excellent resistance” to most chemicals, UV radiation, and micro-organisms” with zero moisture absorption. We’ve machined UHMW components for dairy equipment that handle daily cleaning with caustic solutions for 2+ years without degradation.
Performance Timeline: UHMW in 10% bleach cleaning solutions shows no visible degradation after 12 months of daily exposure. The same exposure would stress-crack Delrin within 6 months under mechanical load.
Hydrocarbon exposure reverses the advantage. UHMW swells when exposed to gasoline and oil, developing 2-4% dimensional growth that binds moving parts. Delrin maintains stability in these environments.
Red Flag Warning: Never use UHMW in continuous fuel contact or Delrin with strong oxidizers under stress.
Cost Override: For short-term chemical exposure, either material may work with frequent replacement scheduling.
Design Takeaway: Match material to primary chemical exposure. UHMW for wet/corrosive environments, Delrin for fuel/oil systems.
What Are the Temperature Limits for Delrin vs UHMW?
Both materials operate continuously up to 180°F (82°C), but UHMW’s heat deflection temperature of 116°F limits structural applications while Delrin maintains strength to its full temperature range. UHMW has Max Continuous Service Temp in Air: 180°F” while Delrin provides “wide operating temperature range (-40 °C to 120 °C)” up to 200°F. However, UHMW’s thermal expansion requires careful machining and mounting accommodation.
Quick Decision Rule: ✓ Below -40°C operation → UHMW only ✓ Structural loads above 116°F → Delrin required
✓ Temperature cycling → Plan for UHMW expansion ✓ Precision required at temperature → Delrin
UHMW has “Coefficient of Linear Thermal Expansion: 7.2 x 10⁻⁵ (in/in/°F)” while UHMW “changes at 2X the rate of nylon with temperature changes. We machine UHMW mounting holes 1.5-2mm oversized per 100mm dimension to accommodate thermal growth. Delrin requires only 0.5-1mm oversizing for identical conditions.
Machining Considerations: UHMW’s “heat deflection temperature is 116°F” means parts deform under clamping forces during hot machining operations. We use flood coolant and reduced feed rates when machining UHMW in heated environments. Delrin maintains rigidity during machining throughout its operating range.
Shop Experience: Fixed-mount UHMW brackets in heated packaging equipment bind within 3-6 months due to thermal expansion. We now recommend designing with oversized slots and spring washers during the machining process. UHMW’s “high coefficient of thermal expansion makes tolerances more challenging to hold” at elevated temperatures.
Dimensional Changes: A 100mm UHMW part grows 1.3mm when heated from room temperature to 80°C. We account for this during machining by adjusting final dimensions based on operating temperature. Delrin grows only 0.7mm under identical conditions.
Design Takeaway: Design UHMW parts with thermal accommodation features during machining phase. Specify oversized mounting features and stress-relief slots. Choose Delrin when maintaining dimensional stability during temperature changes is critical for proper fit and function.
Are Delrin and UHMW Safe for Food Contact Use?
UHMW provides broader food contact compatibility with zero water absorption and no porosity issues, while Delrin has FDA-approved grades but with machining challenges due to centerline porosity. Delrin “has much more centerline porosity than acetal due to the gassing that occurs during manufacturing” which creates visible defects during machining and “provides areas where bacteria can grow in food processing applications”.
Quick Decision Rule: ✓ Direct food contact, visible quality critical → UHMW ✓ Non-critical food equipment → Either works with proper grades ✓ Clean machined surface finish required → UHMW preferred ✓ Budget-critical non-contact → Delrin acceptable
Machining Quality Issues: Centerline porosity “can cause problems during machining” – we see this as surface streaking during face milling and inconsistent surface finish on turned parts. UHMW machines to consistent Ra 3.2μm finish while Delrin’s porosity creates Ra 4.0-6.3μm variations that require secondary finishing for food applications.
Material Specification: Delrin is certified for use by the FDA certified by the NSF and USDA” , but “Delrin is easily attacked by acid foods” and requires specific grade selection. We recommend specifying copolymer acetal instead of Delrin homopolymer to eliminate porosity machining issues.
Shop Experience: During face milling operations, Delrin’s centerline porosity appears as visible lines or streaks that require additional finishing passes. UHMW cuts cleanly with no porosity-related surface defects, reducing machining time by 15-20% for food-grade surface finishes.
Surface Finish Requirements: Food contact parts typically require Ra 1.6-3.2μm surface finish. UHMW achieves this with standard carbide tooling while Delrin often needs diamond tooling or secondary polishing to mask porosity effects.
Design Takeaway: Choose UHMW when machined surface quality is critical for food contact applications. Specify copolymer acetal instead of Delrin to avoid centerline porosity machining complications. UHMW’s consistent machining characteristics reduce finishing operations and improve surface cleanliness.
Should I Choose Delrin or UHMW for My Application?
The decision depends on your primary requirement: choose Delrin for precision assemblies requiring tight tolerances and dimensional stability, or UHMW for harsh environments prioritizing wear resistance and chemical durability. From our machining experience, successful material substitution requires understanding how each material behaves during fabrication and adjusting machining parameters accordingly.
Machining-Based Decision Framework: ✓ Tight tolerances (±0.01mm) required → Delrin for consistent cutting ✓ High-wear sliding applications → UHMW for extended service life ✓ Clean surface finish critical → UHMW avoids porosity issues ✓ Temperature cycling environment → Design for UHMW expansion
Material Change Machining Impact: Switching from Delrin to UHMW requires adjusting feed rates (reduce by 20%), adding flood coolant, and allowing looser tolerances. UHMW’s “heat deflection temperature is 116°F” means heat from machining can cause part deformation if cutting parameters aren’t adjusted properly.
Tooling Considerations: UHMW’s abrasive nature reduces carbide tool life by 25-30% compared to Delrin. We factor this into project costs – typically adding $0.20-0.35 per part in tooling costs for UHMW production runs. Sharp tools are critical for both materials but especially important for UHMW to prevent melting.
Fixturing Requirements: UHMW’s softness requires modified clamping – we use larger contact areas and reduced clamping forces to prevent deformation. Delrin can be fixtured with standard methods. This affects setup time and may require custom fixture design for complex UHMW parts.
Setup Time Differences: UHMW parts typically require 20-25% longer setup time due to specialized fixturing and cutting parameter optimization. Delrin machines similarly to metal with standard setups, making it faster for prototyping and small runs.
Quality Control: Delrin’s centerline porosity is visible during CMM inspection – appears as surface irregularities that can affect measurement accuracy. UHMW provides consistent, homogeneous structure for reliable dimensional inspection.
Design Takeaway: Choose materials based on machining requirements as much as performance needs. UHMW when wear life justifies additional machining complexity. Delrin when machining precision and setup efficiency are priorities. Plan for different tooling, fixturing, and cycle times when switching between materials.
Conclusion
UHMW can replace Delrin when wear resistance and chemical durability outweigh precision requirements. Choose Delrin for tight tolerances and dimensional stability. UHMW works best in harsh, high-wear environments with relaxed tolerances. Contact us to explore manufacturing solutions tailored to your plastic machining requirements.
Frequently Asked Quesitons
Delrin machines like engineered plastic with standard parameters, consistent surface finish, and predictable dimensional accuracy. UHMW requires specialized techniques – reduced feeds, flood coolant, modified fixturing, and sharp tools to prevent melting. Delrin typically reduces machining time by 15-20% and setup complexity, making it more cost-effective for precision work and prototyping.
No, UHMW typically achieves ±0.025mm tolerances while Delrin consistently holds ±0.01mm due to material deflection during cutting. UHMW’s softness causes it to push away from cutting tools, making tight tolerances difficult. For precision work requiring ±0.01mm or better, specify Delrin to avoid manufacturing problems and rework costs.
UHMW is preferred for direct food contact due to zero porosity and excellent chemical resistance. Delrin has FDA-approved grades but centerline porosity creates machining quality issues and potential bacterial harboring sites. For food processing equipment, specify UHMW to eliminate porosity-related surface defects and simplify cleaning validation requirements.
When switching from Delrin to UHMW, relax tolerances by 2-3x, add thermal expansion clearances (1.5-2mm per 100mm), and plan for softer material behavior. When switching from UHMW to Delrin, you can tighten tolerances but may need to strengthen designs for impact loads and consider cold-temperature brittleness limitations.
Yes, expect 15-25% longer machining times and 25-30% higher tool wear costs with UHMW. However, material savings of 20-30% often offset these increases for production runs over 200 parts. UHMW requires flood coolant, specialized fixturing, and modified cutting parameters that add setup complexity but improve part performance in wear applications.
UHMW performs better at temperature extremes but requires design accommodation for thermal expansion. It remains tough below -40°C where Delrin becomes brittle, but loses structural integrity above 116°F. Design UHMW parts with oversized mounting holes and stress-relief features. Choose Delrin for applications requiring dimensional stability through temperature cycles.
