This is based on Thingiverse #4867466.

The original has a few problems, but the big one is that the number wheel has the wrong number of teeth. As a consequence, only half the numbers will line up with the window, and it's impractical to use it by feel without accumulating error. Note that unlike everyone else, I didn't conspicuously avoid taking photos with odd numbers selected.

I used SCAD to fix the wheel teeth, some geometry artifacts on the parts, and provide optional clearances for assembly. I made the keychain boss tall enough that it can act as a secondary constraint on the lid. I also added some chamfers on the keyring hole and the number window for obvious reasons.

The SCAD file does have some parameters that can be adjusted (clearances, number of teeth), but I'm just including STLs with 20t and 30t wheels. All parts are in one STL, oriented as to be printed.

I still don't like the ergonomics, but this is where I'm drawing the line. I told myself I wouldn't start from scratch for something as simple as this, but that tends to be the only sensible way to get anything done right. Instead, I wasted a bunch of time trying to modify STLs in SCAD.

EDIT: The original design (and the main models here) implement the numbers by creating recesses in the wheel which can be filled with paint or something. I added an optional SCAD file (and STLs) to print an alternate wheel with embedded text. It's a little more of a hassle, but it doesn't require a multimaterial printer. See the internal notes and the photos.

Category: Hobby