Delrin vs Nylon in CNC Machining Applications

When customers ask us to machine plastic parts, one question comes up almost every week:

“Should we use Delrin or Nylon for CNC machining?"

On paper, both look similar.
In real factory production, however, the difference is huge.

Over the past 12 years running CNC machining for industrial buyers, we’ve processed 50,000+ Delrin and Nylon components for gears, bushings, sliders, wear plates, and automation parts.

We’ve seen:

• Nylon warp after humidity exposure

• Delrin hold ±0.01 mm tolerance for months

• Wrong material choices cause 30–40% scrap rate

This guide shares real machining data, practical fixes, and buyer selection advice — not textbook theory.

Quick rule we use in our factory:

• Tight tolerance → Delrin

• Shock load or abrasion → Nylon

Delrin (Polyoxymethylene / Acetal / POM) is one of the most dimensionally stable engineering plastics we machine.

When milling Delrin:

• Chips break cleanly

• No stringing

• Minimal heat build-up

• Tool wear very low

This means:
✔ faster feed rates
✔ better surface finish
✔ stable tolerance after machining

Material: 20 mm plate
Process: CNC milling

Delrin clearly wins for precision mechanical assemblies.

• Precision gears

• Bushings

• Linear slide blocks

• Robot components

• Semiconductor fixtures

Nylon (PA6 / PA66) is tougher and more impact resistant.

However, from a machining standpoint, it’s more “difficult".

• Stringy chips wrapping tools

• Heat deformation

• Moisture swelling

• Post-machining warping

In summer (humidity > 70%), we measured 0.15–0.25 mm growth on 200 mm parts within one week.

For tight tolerance jobs, this becomes a serious issue.

✔ heavy load
✔ sliding friction
✔ impact shock
✔ low cost required

• Wear pads

• Conveyor rollers

• Heavy-duty bushings

• Impact guards

• Agricultural machinery parts

Follow this process we use with B2B customers:

• ±0.02 mm or tighter → Delrin

• ±0.05 mm → Either works

• High humidity → Avoid Nylon

• Outdoor use → Delrin safer

• Continuous wear → Nylon

• Precision motion → Delrin

• Low cost priority → Nylon

• Performance priority → Delrin

Part: Linear guide slider
Tolerance: ±0.015 mm

Originally used: Nylon

Problems:

• Warping after assembly

• Jamming on aluminum rail

• 18% rejection rate

Changed to Delrin (POM-C)

Results:

• Tolerance stable

• Friction reduced 22%

• Scrap rate → 2%

• Lifetime increased 1.8*

Customer saved ~$12,000/year in maintenance.

This is why we now default to Delrin for precision motion parts.

• Use sharp carbide tools

• High feed, medium speed

• No coolant needed

• Achieve mirror finish easily

• Use air blast cooling

• Lower speed to avoid melting

• Rough + finish passes

• Pre-dry material before machining

Drying Nylon alone reduced our warping issues by 40%.

Although Delrin costs ~15–25% more,
total cost per good part is often lower due to reduced scrap.

✅ Tight tolerance
✅ Precision assemblies
✅ Stable dimensions
✅ Smooth finish

✅ High impact strength
✅ Heavy wear resistance
✅ Budget solution
✅ Low precision requirement

Delrin is stiffer and more dimensionally stable, but Nylon has better impact resistance.

Delrin machines much cleaner with better tolerance.

Yes, 2–7%, which can cause swelling and deformation.

Nylon is cheaper in raw cost, but Delrin often reduces total machining waste.