How to print a bolt and nut that fit
- Pick the part and size. Metric M3–M24, UNC #10–1", or any custom diameter and pitch.
- Choose what it mates with. “Another printed part” splits the clearance between bolt and nut; “standard metal hardware” puts it all on the printed part.
- Print a nut first and try it on your bolt. Too tight: raise the clearance by 0.1 mm. Loose: lower it.
- Download the STL. Bolts print head-down, rods and standoffs standing up, nuts and washers flat – exactly as the file is laid out.
Recommended print settings
| Setting | Value |
|---|---|
| Material | PETG or nylon for strength; PLA for prototypes |
| Layer height | 0.12–0.16 mm (finer layers = smoother threads) |
| Walls | 4 or more |
| Infill | 40–100% for bolts and rods |
| Orientation | As downloaded – threads vertical |
| Supports | None |
Making gears for a shaft? The Gear Bench adds set screws and nut traps to gear hubs.
Frequently asked questions
What is the smallest thread that prints well?
With a 0.4 mm nozzle, M6 and larger print reliably. M3–M5 threads can work on a well-tuned printer at 0.1 mm layers, but for small sizes a heat-set insert or a metal screw is usually the better choice – the spacer option makes the insert holes for you.
How much clearance should I use?
Start with the default 0.3 mm. If a printed bolt and nut are tight, go up to 0.4–0.5 mm; if they wobble, go down to 0.2 mm. Choose “fits standard metal hardware” when the part must mate with a real metal bolt or nut – then all of the clearance goes on the printed part.
Do these fit real metric and UNC hardware?
Yes. The thread profile follows ISO 68-1 (the same 60° profile as UNC), with ISO 261 metric pitches and ASME B1.1 threads per inch. Heads, nuts and washers use ISO 4017, 4032, 4762, 7089 and ASME B18 sizes. Printers vary, so print one nut first to check the fit.
How should I print bolts and nuts?
Print bolts standing up, head down, and rods and standoffs standing up, so the thread is formed by the layers. Print nuts and washers flat. Use 0.12–0.16 mm layers, 4 walls and PETG or nylon for strength. No supports are needed.
Are printed bolts as strong as metal ones?
No – a printed bolt is a small fraction of the strength of a steel bolt. Use them for jigs, prototypes, knobs, covers and light fixtures, not for anything that carries a load where failure could hurt someone.
Can I make left-hand or multi-start threads?
Yes. Pick left hand for parts that must not loosen when turned the other way, and 2–4 starts for fast-acting threads such as lids and clamps. The bolt and its nut must use the same settings.