Delrin (Acetal / POM) – CNC Machining

Delrin is used for CNC machined components where low friction, dimensional repeatability, and predictable wear behavior are required in precision mechanisms.

Its machining behavior is characterized by clean chip formation and low cutting forces, allowing tight tolerances when thermal input is controlled.

At ShvaveyMetal, Delrin CNC machining workflows are defined around stable cutting parameters, sharp tooling, and finishing passes that preserve geometry and surface quality.

Delrin is a brand name for acetal homopolymer (POM-H), selected over acetal copolymers when higher stiffness, better machinability, and improved fatigue resistance are required.

Mechanical Properties (Typical)

Property Typical Value Units
Density ~1.41 g/cm³
Tensile Strength ~65–75 MPa
Yield Strength ~60–70 MPa
Elongation at Break ~25–40 %
Elastic Modulus ~3.0–3.3 GPa
Hardness ~120–125 Rockwell M

Mechanical properties are relatively stable and less moisture-sensitive compared to polyamides.

Thermal & Physical Properties

Property Typical Value Units
Melting Temperature ~175–180 °C
Continuous Service Temperature ~90–110 °C
Thermal Conductivity ~0.31 W/m·K
Coefficient of Thermal Expansion ~100–110 µm/m·K

These properties support predictable dimensional behavior during CNC machining.

Chemical Resistance (General)

Substance Category Resistance Level
Water / Aqueous Solutions Excellent
Oils and Greases Excellent
Alcohols Good
Fuels Good
Strong Acids / Alkalis Poor
Oxidizing Agents Poor

Chemical resistance depends on exposure time, temperature, and applied stress.

Delrin machining behavior is dominated by its stiffness, low friction, and favorable chip formation.

Key machining characteristics include:

  • Clean, broken chips with minimal stringing
  • Low cutting forces enabling tight tolerances
  • Excellent surface finish achievable without polishing
  • Minimal tendency for edge melting compared to many thermoplastics
  • Good dimensional repeatability in multi-operation parts

Machining is typically performed dry or with air blast using sharp carbide tools and stable cutting parameters.

Benefit Description
Excellent Machinability Predictable cutting behavior and tool response
Low Friction Suitable for sliding and rotating components
Dimensional Stability Maintains geometry better than moisture-sensitive plastics
Good Wear Resistance Performs well in repeated motion assemblies
Tight Tolerance Capability Supports precision polymer components

Delrin is commonly used for CNC machined components such as:

  • Bushings, bearings, and wear pads
  • Gears, sprockets, and cam components
  • Precision spacers, rollers, and guides
  • Valve components and fluid-handling parts
  • Mechanical assemblies requiring low friction and repeatability

Application suitability depends on load, temperature, and chemical exposure.

Variant General Characteristics
Delrin (POM-H, Homopolymer) Higher stiffness and superior machinability
Acetal Copolymer (POM-C) Improved chemical resistance, slightly lower stiffness
Filled Acetal Grades Enhanced wear or stiffness with reduced machinability
FDA / Food-Grade Variants Used where regulatory compliance is required

Machining behavior differs between homopolymer and copolymer acetals and should be specified clearly.

  • Avoid sharp internal corners that concentrate stress
  • Allow for thermal expansion in long or constrained parts
  • Define surface finish requirements for bearing interfaces
  • Avoid exposure to strong acids or oxidizing environments
  • Select homopolymer versus copolymer early based on performance needs

Clear definition of operating environment improves material selection accuracy.

FAQ

How well does Delrin machine?

Delrin is among the best-machining engineering plastics, producing clean chips and excellent surface finishes. Sharp tooling with polished flutes, high spindle speeds and effective chip clearance give the best results. Its relatively high thermal expansion means temperature should be controlled during both machining and inspection of tight-tolerance parts.

What is Delrin, and is it the same as acetal?

Delrin is DuPont's trade name for acetal homopolymer (POM-H). Acetal copolymer is a related but distinct material with slightly lower stiffness and strength, better resistance to hot water and alkaline conditions, and without the centreline porosity that can occur in thick homopolymer stock. The required form should be specified on the drawing.

What tolerances can be held on CNC machined Delrin parts?

Delrin holds tight tolerances well by plastics standards, thanks to good dimensional stability and low moisture absorption. The limiting factor is usually thermal expansion, roughly ten times that of steel, so tolerances should be specified at a stated temperature and inspection carried out under controlled conditions.

What are CNC machined Delrin components used for?

Typical applications include gears, bearings, bushings, rollers, valve components, manifolds, insulators and precision mechanical parts. Delrin is frequently used to replace metal where low friction, wear resistance, reduced weight or quieter operation are advantageous under moderate loads.

What are the limitations of Delrin in machined components?

Delrin has limited resistance to strong acids and to prolonged hot water or alkaline exposure, and it is not suitable for high temperature service. Thick homopolymer rod can exhibit centreline porosity, which matters for parts machined from the bar centre, so copolymer grades are often specified instead.


Why Machine Delrin at ShvaveyMetal

ShvaveyMetal machines Delrin using CNC processes optimized for dimensional repeatability, surface quality, and functional wear behavior.

This approach supports reliable Delrin machining services for precision polymer components across prototype and production programs.