A 3D-Printed Watch Case With a Bayonet-Mount Back

I love to see 3D printed models that require as few hardware and non-3DP parts as possible. I have always use M1.6 screws for fastening the case-back but these can be fiddly. Z0hn has developed an innovated method of fastening down the caseback using a twist and lock mechanism

What They Built

The project is a complete watch case, printable on an ordinary FDM 3D printer, designed to hold a standard off-the-shelf Miyota 8N24 movement and a stock crystal.

How They Did It

Printed threads and screw-down backs are notoriously unreliable on FDM printers — layer lines and dimensional tolerances make fine threads gritty or loose, and they tend to strip out over repeated opening and closing. Z0hn’s case sidesteps the problem with a bayonet-style twist-lock back instead: a quarter-turn connector that’s far more forgiving to print accurately and holds up better to daily handling than threaded alternatives. The rest of the design is built to be easy to modify, with details like crown placement left open for makers to adapt to their own movement or wrist preferences.

Go See It

Z0hn published the full build and downloads on Instructables as “Building Your Own Custom Watch From Scratch,” a step-by-step guide covering the case design and assembly. Hackaday featured the project on June 13, 2026.