Delrin vs Nylon 6 for Machined Bushings and Gears

Delrin vs nylon 6 is a common choice for machined bushings, gears and wear parts, and the two plastics look alike on the shelf. They behave differently once the part is in service.

Should You Machine a Bushing or Gear From Delrin or Nylon 6?

Pick Delrin when the part has to hold its size and run smoothly, such as precision gears and bushings on a smooth shaft. Pick nylon 6 when the part takes impacts, runs against a rough or dirty surface, or when tight dimensions matter less than toughness.

An r/CNC user building a DIY pick-and-place head asked which to use. One reply said Delrin machines better, but only marginally, and that nylon is cheaper. Others said Delrin is a fair amount stiffer, and that nylon absorbs moisture and swells, so it's best avoided where dimensions are critical.

Delrin vs nylon 6: what changes in service

• Moisture. This is the big one. OpenSpindle's comparison puts cast nylon 6 at roughly 6 to 7 percent water at saturation, against about 0.8 percent for acetal. Nylon parts machined dry can grow as they pick up water.
• Stiffness and tolerance. The same guide says acetal is stiffer and holds tighter tolerances.
• Friction. Acetal has lower friction, which suits dry-running bushings and precision gears on smooth shafts.
• Toughness. Nylon has better impact and abrasion resistance, so it suits parts that get struck or run against rough or contaminated counterfaces.

Delrin is DuPont's trade name for acetal homopolymer. There is also acetal copolymer, and OpenSpindle notes that most shops read Delrin on a drawing as any acetal.

What to put on the drawing

Call out the material by name. If a nylon 6 dimension is fit-critical, OpenSpindle suggests stating whether it applies dry as machined or after the part has conditioned. If you're unsure the part can live with any dimensional change, that's usually a sign to use Delrin.

Printing the part instead? See moisture absorption in SLS and MJF PA12 parts.

Related: snap fits in MJF nylon vs machined Delrin and why tapped holes in printed nylon strip sooner.

At DigiForge

Our materials page lists both for CNC machining: Delrin for bearings, bushings and precision plastic parts, and Nylon 6 for wear parts, gears and insulators. You can upload a part and switch materials to compare. If the part needs homopolymer or copolymer specifically, ask us when you quote.