Nylon filament: print bolts that act like real hardware

Go to the fastener aisle at any hardware store and look at the bottom shelf.

There's a little bag of white plastic bolts and nuts. Nylon.

They're not the cheap version. They're there on purpose — for electrical work, boats, anything that can't rust or conduct. And that colored ring inside the lock nut in your bin? Also nylon.

So when people ask what filament to print hardware out of, nylon filament's got a head start. It's already been hardware for decades. It's slick, it's tough, it bends instead of snapping, and it barely cares if you drop it.

The catch: it drinks water, it warps, and it's pickier to print than anything you've used so far. Let's deal with all of that.

Nylon is already hardware

McMaster-Carr describes their nylon 6/6 screws as "chemical and oil resistant, nonconductive, and lightweight." DuPont's design guide for their Zytel nylon adds that it's not affected by electrolytic corrosion around salt water, and gets used in electrical parts up to 600 volts.

My favorite stat from that guide: in a repeated-impact test, nylon 66 survived 250 hits. Die-cast zinc survived 7.

Seven!

And that nyloc nut? The nylon insert works because it deforms elastically over the bolt threads and grips them. Way more on where that came from in the history post — including why you shouldn't put one near your hotend.

Why it's so good for threads

It's slippery. Prusa calls nylon "very low friction" and recommends it for gears and bushings. Nylon on nylon is especially slick — DuPont lists a dynamic friction coefficient of about 0.11–0.19. Threads that glide instead of grind.

It's tough. It flexes instead of shattering. A nylon thread crest bends where a PLA one would chip right off.

It creeps, and that's a feature and a bug. DuPont points out nylon's tendency to slowly relax under load is exactly why it's good for self-threading screws and locking nuts — it molds itself around the threads. But it's also why a nylon bolt clamped tight will loosen over time. CNC Kitchen found un-annealed carbon-fiber PA6 needed re-tightening "almost every day" for a week. Annealed? Much better. PA12? Only once.

The catch: it drinks water

Nylon pulls moisture straight out of the air. Prusa says it can absorb up to 10% of its own weight. Wet nylon prints like hot garbage. Rough, stringy, weak as hell.

So: dry it every single time. Real numbers from datasheets:

• Prusa (general nylon): at least 4 hours, under 90°C.
• Prusament PA11: 90°C for 6–8 hours.
• Bambu PA6-CF / PAHT-CF: 80°C for 8–12 hours, then store it under 20% humidity.
• Polymaker PA6-CF: 80°C for 12 hours.

A filament dryer that you can print straight out of is the move. A ziplock with a desiccant pack is a nice thought. It's not enough.

The twist: wet nylon is tougher

Here's the weird part.

You dry nylon to print it. But once it's a part, a little moisture is good for it.

DuPont's numbers for molded nylon 66, bone-dry vs soaked to normal room humidity (50% RH):

| | Dry | At 50% humidity | |---|---|---| | Tensile strength | 83 MPa | 77 MPa | | Stiffness (flex modulus) | 2827 MPa | 1207 MPa | | Impact strength (Izod) | 53 J/m | 112 J/m |

A little weaker. Less than half as stiff. But twice as tough. Moisture turns it from rigid into springy.

CNC Kitchen saw the same thing in printed carbon-fiber nylon. After sitting in 75% humidity, PA6 kept only 56% of its strength, its stiffness dropped to a third, and its impact energy more than tripled. PA12 barely noticed — it kept 85% of its strength, because it only soaked up about 0.7% water versus about 3% for PA6.

Two practical things fall out of that:

• It grows. DuPont lists about 0.6% dimensional growth at 50% humidity. On a 50 mm part, that's 0.3 mm. Leave a little extra clearance on anything that has to fit.
• It takes forever. A 1.5 mm thick part takes about 125 days to fully settle at room humidity. If you want it tough now, DuPont's trick for molded parts is boiling — a 3.2 mm part gets there in about 3 hours.

(Fun fact: in Phoenix, my nylon basically never gets wet. If you're in Florida, your nylon's gonna be a very different material by August.)

PA6 vs PA12 vs carbon fiber

• PA6: strongest when dry, but the most moisture-sensitive. Big swings in stiffness.
• PA12 (and PA11): more stable. Takes on less water, changes less, creeps less.
• Carbon-fiber or glass-filled nylon: much stiffer and warps waaayyy less. Prusa says CF nylons can even be printed without an enclosure. They need a hardened nozzle — the fiber will eat a brass one alive.

Heat numbers, because they're wild: Bambu's PAHT-CF lists a heat deflection temp of 170–194°C. Prusament's plain PA11 is just 58.7°C as printed — but 122.5°C after annealing. If you want unfilled nylon to handle heat, you bake it.

And unlike PLA, annealing CF nylon doesn't wreck the part. CNC Kitchen annealed theirs at 110°C for 8 hours and saw under 0.5% warp.

How to print it

• Dry it (see above), and print from the dryer if you can.
• Hot nozzle. Polymaker's PA6-CF runs 280–300°C. Make sure your hotend is rated for that before you try.
• Bed: Prusa sells a dedicated nylon sheet. Bambu recommends their PVP glue stick. Polymaker says glue or Magigoo. Nylon does not want to stick to a bare plate.
• Enclosure for plain nylon — it warps hard. CF versions are much more forgiving.
• Hardened nozzle for anything with fiber in it.

Once you dial it in, write it down — dry time, temps, which bed surface worked — as a 3D printer setup in the Machine Setups Repository. Nylon is the filament where you really don't want to rediscover your damn settings from scratch.

What to make with nylon

This is the fun part:

• Gears. Low friction, tough teeth. DuPont has a story of nylon worm gears running 18 months straight.
• Bushings and sliders. Anywhere two parts rub.
• Thumbscrews and nuts for jigs you adjust every day.
• Living hinges and snap-fits. Nylon bends back over and over where PLA would crack on the third try.
• Washers, spacers and cable clips. The boring stuff that has to survive.

And for the threads themselves, the Nasty Bastard bolt maker builds matched nut-and-bolt pairs with the printed clearance built in. For nylon, give it a little extra — remember, it grows. If you're still picking between materials, here's how nylon stacks up against PLA, PETG and the rest.

So what's the first thing in your shop that keeps breaking that should've been nylon all along?

Frequently asked questions

Is nylon filament good for 3D printed nuts and bolts?

Yes. Nylon is what many commercial plastic fasteners are made of — it's tough, low friction, corrosion resistant and nonconductive. The tradeoffs are that it must be dried before printing, warps without an enclosure (unless fiber-filled), and creeps under constant clamping load unless annealed.

How long do you dry nylon filament?

Follow the spool's datasheet. Examples: Prusa recommends at least 4 hours under 90°C for nylon in general and 90°C for 6–8 hours for Prusament PA11; Bambu recommends 80°C for 8–12 hours for PA6-CF and PAHT-CF, then storage under 20% humidity.

What's the difference between PA6 and PA12 nylon filament?

PA6 is stronger when dry but absorbs much more moisture (about 3% vs 0.7% in CNC Kitchen's test), so its stiffness and strength swing more with humidity and it creeps more. PA12 is more stable and dimensionally consistent.

Does nylon get stronger when it absorbs moisture?

Tougher, not stronger. In DuPont's data for nylon 66, conditioning to 50% humidity cut stiffness by more than half and slightly lowered tensile strength, but roughly doubled impact strength. It also grows about 0.6% in size, so leave extra clearance on fitted parts.