FittingsFab — 3D printable NPT pipe coupling designer
Coupling Designer · fittingsfab.com
FittingsFab
A parametric configurator for hollow plumbing couplings. Pick NPT sizes for each end, see live dimensions, and export a print-ready STL with true tapered threads and a full water passage.
Design the coupling.
Every coupling is three sections: the left end, a hex body, and the right end. Water flows straight through. Pick a thread spec and length for each. The drawing updates live.
recessed socket — accepts a stud
barrel between the two ends
Max ⌀22.4 mm keeps safe wall thickness.
recessed socket — accepts a stud
Inspect the 3D model.
Real helical thread geometry, not a decorative texture. Drag to orbit, scroll to zoom.
Download 3D model and print.
Print the final version.
Your test print told you the shape is right. Now make the same part in something that holds pressure — on your own printer, or ordered from a print shop.
Hot water, pipework hidden in a wall, or anything you cannot reach to check for leaks: skip printing and order stainless 316L or bronze instead.
- Print at 0.12–0.16 mm layers on your own printer.
- Screw it onto the real pipe by hand — no tape.
- Check it seats without wobble and the hole lines up.
Tip: test fit a PLA copy first — it costs cents, a metal part does not.
Material: Nylon PA12 (SLS / MJF), finish: vapor smoothing, qty 1. Threaded part: 3/4" FNPT x 1" FNPT. Do not reduce wall thickness or modify threads.