CNC Machining Nylon
Nylon is the wear plastic: bushings, gears, rollers and guides that run against metal without lubrication and stay quiet doing it. It is tough, it resists impact, and it has one property that catches out every engineer who meets it for the first time — it absorbs water from the air, and it grows.
Grades we machine
Cast and extruded nylon behave differently enough that the distinction belongs on the drawing for anything large or tightly toleranced.
| Grade | Best for | Notes |
|---|---|---|
| Nylon 6 (cast) | Large parts, thick sections, wear components | Cast stock has lower internal stress than extruded, so big parts move less after machining |
| Nylon 6/6 (extruded) | General purpose parts, bar stock components | Stiffer and harder than nylon 6, more readily available in small sections |
| Oil-filled nylon | Self-lubricating bushings and gears | Internal lubricant makes it run cooler and quieter against steel |
| MoS2-filled (molybdenum disulphide) | Higher load bearing surfaces | Black, slightly stiffer, better under load than unfilled |
| Glass-filled nylon | Stiffness and dimensional stability | Abrasive on tooling; less tough than unfilled |
Tough to cut, and it moves
Nylon is soft and ductile, so it deflects away from the cutter and tends to string rather than chip. Sharp, high-rake tooling and a real feed rate keep the cut clean; a dull tool smears and melts it. Thin walls and long unsupported sections deflect noticeably more than they would in acetal.
The property that matters most is moisture. Nylon absorbs water from the air and expands measurably as it does — enough to move a fit on a large part. A part machined and measured in a dry workshop will be slightly larger after a few weeks in a humid environment. That is the material, not the machining, and the way to handle it is to design a fit with tolerance for it rather than to demand a tighter tolerance.
For precision parts, we rough, let the part relax, then finish, and we measure after the part has reached room temperature.
| At a glance | |
|---|---|
| Service temperature | Around 80–100 °C |
| Moisture absorption | Significant — the defining property of the material |
| Machinability | Fair; deflects and strings, needs sharp tooling |
| Friction | Low against steel, especially oil-filled grades |
| Typical parts | Bushings, gears, rollers, wear strips, guides, insulating parts |
Three notes on nylon parts
Design the fit to tolerate growth
A press fit sized exactly in a dry room can become an interference in a humid one. Tell us the service environment and we will flag any dimension that is at risk.
Choose cast nylon for big parts
Cast stock carries less internal stress than extruded, so large machined parts stay closer to the shape they left the machine in.
Do not expect acetal tolerances
If the part must hold a tight fit and the environment varies, acetal is usually a better answer than a tighter tolerance on nylon.
PA66 milled from solid. The long pale chips are what you want to see — nylon cuts cleanly with a sharp tool, but it is soft enough to push away from the cutter, so the finishing pass stays light and the fixture matters more than the feed rate.
Finishes that work on nylon
Nylon is used as machined. Colour comes from the stock rather than from any coating.
Finishing is done by partner shops we specify and inspect for — we do not run plating or coating tanks ourselves. How we handle finishing →
Send the bushing or gear drawing
Send the drawing and the grade, or the drawing and a sentence about what the part has to survive. You get a price, a lead time, and an engineer’s note on anything that will fight the tolerances.