Designing to a standard: the new Learn guide for parts that fit what you already own
A new guide in Kapy CAD's Learn hub: Gridfinity, Skådis, LEGO, VESA, 2020 extrusion, bottle threads and IKEA. 39 articles —in English and Spanish— on the shared dimensions that let a printed part drop into an ecosystem someone already owns, and what FDM does to those tolerances.
The best part you print is often not the one you design whole, but the one that fits something you already own: a bin that drops into a Gridfinity drawer, a hook that grabs your Skådis, an adapter that threads onto a bottle, a foot that seats in a Kallax. There you don't pick the dimensions — a standard shared by thousands of people does, and your job is to hit it to a tenth of a millimetre, with the added catch that FDM moves exactly those dimensions.
So we wrote Designing to a standard, the new Learn guide: the map of the ecosystems worth printing to fit, with the real dimensions and the tweak each one needs so it comes off the bed and clicks on the first try.
What's inside
39 articles across 7 sections, each with the official measurement, the tolerance printing imposes, and the catalog part ready to fork:
- Organization and storage — Gridfinity and the systems that grew beside it: the 42 mm grid, the feet, the stacking lips and the dividers.
- Panels and wall mounting — Skådis, imperial pegboard, slatwall, NATO rails and the French cleat: the hole patterns and hook profiles that turn a wall into storage.
- Construction and toys — LEGO System and Technic, Duplo, Playmobil, Meccano: studs, pins and cross axles, where a tenth decides whether the clutch grips.
- Photo, video and mounts — GoPro fingers, Arca-Swiss dovetail, the 1/4-20 tripod thread and quarter-turn plates: the standards that connect cameras to everything.
- Electronics, workshop and structure — 2020 aluminium extrusion, DIN rail, Raspberry Pi and Arduino footprints: the patterns that hold the electronics and the machines that build them.
- Threads and containers — PET necks, jar mouths, garden-hose thread: the real thread standards you can print a cap or an adapter for.
- Furniture and home — Kallax, Lack, Trofast, Besta, Ivar/Pax: the IKEA measurements worth knowing so an insert or a leg fits first time.
A printed standard isn't the nominal standard
What sets this guide apart is that the official number is almost never the number you draw. A couple of examples of what you'll find:
- Why an exact 4.8 mm LEGO stud won't grip. The clutch doesn't live in the nominal diameter but in the interference between stud and tube, and FDM fattens it on one side and eats it on the other. The dimension you print isn't the one on the box.
- Why your Gridfinity stacks crooked. The 42 mm is the easy part; what makes a bin centre on the one below is the foot chamfers and the lip clearance, not the grid pitch.
- Why a rocking Skådis hook falls off. The Skådis pattern isn't just any grid: its oblong slots want a two-prong hook that enters straight and then drops, so both barbs catch behind the panel.
And when it's time to print a cap, not all threads are equal: a sharp V, a buttress or a trapezoidal form behave — and print — very differently.
With the official dimensions and the part that meets them
Like the rest of Learn, it's not theory: every article carries the standard's measurement, reasons about the fit FDM asks for, and ends in a parametric catalog part that already meets those dimensions — ready to fork and adapt to your case.
And we keep going
Every new standard the catalog supports brings its article, its animation and its ready-to-use part. Head over to the learn section, see which ecosystem you're about to print, and tell us which one is missing — we'll write it.
Written by
Sergio
Building Kapy CAD — parametric 3D modelling for 3D printing, in the browser.
