Gears & cams
Quiet running, self-lubricating, durable. Common in office equipment, small appliances, automotive auxiliary drives.
Polyoxymethylene · Acetal homopolymer
Delrin / Acetal POM
The general-purpose engineering plastic. Strong, stiff, dimensionally stable, low-friction, and easy to machine. Goes into gears, bushings, snap-fit components, fluid-handling parts, and anything where a metal is overkill but a softer plastic isn't enough.
UTS
70 MPa
Density
1.42 g/cc
Service T
100 °C
Mach.
80 /100
When to use
Pick Delrin when a plastic is the right call.
Delrin (DuPont’s trade name for acetal homopolymer) is the engineering plastic that’s tough enough for gears, stiff enough for snap-fits, low-friction enough for bushings, and easy enough to machine that small custom parts come back in days. POM stands for polyoxymethylene — the polymer family. Homopolymer (Delrin) is stiffer and stronger; copolymer (Celcon, Hostaform, Acetron) is more chemically resistant.
The trade-offs are predictable: lower strength than metal, sensitive to UV, melts above ~175 °C, can outgas slightly. For environments above 100 °C continuous, step up to PEEK. For higher chemical resistance, choose acetal copolymer over homopolymer.
Strengths
Why Delrin is the default plastic.
- Easy to machineMach 80/100 — among the friendliest plastics. Sharp tools, fast cycles, clean surface finish.
- Low frictionμ ~0.20 against steel, dry. Standard for unlubricated dynamic seals, bushings, sliding components.
- Dimensionally stableLow water absorption (~0.25%) and good thermal stability under load. Fits stay fit.
- StiffModulus 3.1 GPa — about 1/20 of aluminum, but 3–4× higher than nylon. Holds shape under sustained load.
- Fatigue tolerantExcellent in cyclic loading. Common gear material for short-life and quiet-running applications.
- Stocked everywhereBlack and white rod, sheet, plate in every size. Cheap and available.
Trade-offs
Where it gives up.
- Limited chemical resistanceHydrolyzes in strong acids, hypochlorite (chlorine bleach), and hot water. Copolymer (Celcon) handles this better.
- UV degradationYellows and embrittles under sustained UV. Use UV-stabilized grades for outdoor service or step up to PEEK.
- Temp ceilingContinuous service to ~100 °C, melt at 175 °C. Above that, look at PEEK or PEI (Ultem).
- Solvent bondsDoesn't easily solvent-weld or glue. Mechanical fastening or ultrasonic welding preferred.
- OutgassingSome grades release formaldehyde at high temp. Not ideal for vacuum or food-contact applications without proper grade.
- Notch-sensitiveSharp internal corners reduce fatigue life. Add radii ≥ 0.5 mm at all stress concentrations.
Specs
Mechanical, physical & thermal data.
Properties for Delrin 150 (homopolymer) — the most common machinable grade. Acetal copolymer values follow in notes.
Mechanical
Properties (homopolymer)
| Tensile strength at yield | 70 MPa (10 ksi) |
|---|---|
| Tensile elongation at yield | 11% |
| Tensile elongation at break | 25 – 75% |
| Tensile modulus | 3.1 GPa |
| Flexural strength | 97 MPa |
| Flexural modulus | 2.8 GPa |
| Compressive strength | 110 MPa |
| Hardness (Rockwell) | M94 / R120 |
| Izod impact (notched) | 75 J/m |
Source: DuPont Delrin 150 datasheet. Copolymer (e.g., Acetron GP): UTS 65 MPa, modulus 2.8 GPa, slightly less strong but more chemical-resistant.
Thermal & physical
At room temperature
| Density | 1.42 g/cc (0.0513 lb/in³) |
|---|---|
| Glass transition (Tg) | −73 °C |
| Melting point | 175 – 178 °C |
| Continuous service | 100 °C (212 °F) |
| HDT (1.8 MPa) | 100 °C |
| Thermal conductivity | 0.36 W/m·K |
| CTE (–40 to 50 °C) | 85 µm/m·°C |
| UL94 flammability | HB |
High CTE (~7× steel) requires expansion clearance in steel-bushed assemblies. Plan ~0.001″ per inch of bore per 10 °C temperature swing.
Physical & chemical
At room temperature
| Water absorption (24 hr) | 0.25% |
|---|---|
| Water absorption (saturation) | 0.9% |
| Coefficient of friction (vs steel) | 0.20 dynamic, 0.20 static |
| Dielectric strength | 20 kV/mm |
| Dielectric constant | 3.7 at 1 kHz |
| FDA / USP VI grades | Available |
Delrin AF (Teflon-filled) has μ ~0.10 — for dynamic seal and slide applications where standard Delrin is too sticky.
Grade selection
Pick the right acetal.
| Grade | UTS | Modulus | Best for |
|---|---|---|---|
| Delrin 150 (homopolymer) | 70 MPa | 3.1 GPa | General machining; gears, bushings, structural plastic |
| Acetal copolymer (Celcon, Acetron GP) | 65 MPa | 2.8 GPa | Better chemical resistance; food, pharma, marine |
| Delrin AF (PTFE-filled) | 55 MPa | 2.5 GPa | Lower friction; dynamic seals, slide bearings |
| Delrin 100AL (lubricated) | 65 MPa | 2.8 GPa | Higher PV — bushings under load |
| Delrin 510GR (glass-filled) | 75 MPa | 8.5 GPa | Higher stiffness; structural plastic parts |
| FDA / USP VI grades | Same as base | Same as base | Food contact, medical short-term |
Specifications
Common purchase specs.
ASTM D6778
Standard for acetal homopolymer (POM-H)
ASTM D4181
Acetal copolymer (POM-K)
MIL-P-46137
Plastic molding compound — acetal
FDA 21 CFR 177.2480
Food contact — acetal homopolymer
ISO 9988
Polyoxymethylene molding/extrusion
USP Class VI
Pharmaceutical contact biocompatibility (select grades)
NSF 51 / 61
Drinking water contact (select grades)
UL94 HB
Standard flammability rating
Machining
How we cut it.
Delrin is one of the easiest plastics to machine. Sharp tools, high speeds, and aggressive feeds. Cycle times comparable to aluminum on simple geometry. Watch for melt and chip welding on slow finishing passes.
Cutting speed
800–1,500 SFM with carbide. Sharp polished tools cut clean — dull tools generate heat that melts surface.
Feed rate
Aggressive constant feed. Plastic doesn't work-harden.
Tooling
Polished carbide preferred. Avoid coatings that grab — uncoated or PCD cuts cleanest on plastics.
Coolant
Air blast or water-soluble. Avoid chlorinated cutting oils — can stress-crack.
No melt zone
If chip color darkens, slow the spindle or take lighter DOC. Surface melt ruins finish and dimensional accuracy.
Anneal for tight tolerance
200 °F (95 °C) for 1-2 hr before machining if part will see thermal cycling. Reduces stress that causes drift.
Threading
Single-point or roll forms preferred. Cut taps work in soft material — sharp HSS or single-flute taps.
Drilling
Slow back out — Delrin can clog drills. Use spiral-flute drills with positive cutting angle.
Applications
Where Delrin shows up.
Bushings & bearings
Dry-running plain bearings, sliding rails, conveyor rollers. Long life under moderate PV.
Fluid handling
Valve bodies, pump impellers, manifolds. Compatible with most water-based fluids and many petroleum products.
Compare
Related materials.
Higher temp / chem
PEEK →
When 100 °C is too cold or chemical resistance has to be top-tier. ~10× the cost.
Stronger / metal
Aluminum 6061 →
When stiffness and strength matter more than weight or chemical isolation.
Heavy-duty bushing
C932 Bronze →
For higher PV bushing applications under load or shock.
Have a part that needs to be made right?
Tell us about your part and we'll quote within 24 hours. Aerospace, medical, and defense work welcome.
Quotes in 24 hours