We have an aging Thermador gas range.  One of the original plastic knobs broke. Surprisingly, it was hard to find replacements.  Thermador no longer supplied them, and the 6mm D-shaft was an unusual size for generic replacements.  The closest I could come was some generic knobs off ebay.  But these didn’t have the proper stop inside the sleeve, so you couldn’t push the shaft in before turning it (a safety feature of the Thermador knobs). I kludged some stops with chopstick pieces, but it was clumsy.  Time to roll our own.

I created this is Fusion 360, using extrusions for the shaft and stopper, surface of revolution for the knob, and the free-form “sculpt” environment for the handle.

I modeled two variants; a one-piece unit and a two-piece unit printable on FDM-style printers that can’t handle overhanging parts.  The two-piece unit assembles with small wood screws.

I tried creating a sample at the UPS Store (there’s a 3D equipped one near our house) but the quality is kind of grim.

Their printer clogged a couple times.  This left the shaft very weak, it snapped off and had to be glued back together.  It was useful as a basic fit test, but not something you’d want to keep in your kitchen. The print cost about $40, mostly due to UPS’s idiotic policy of charging for the bounding box of the print, not the actual print time or material consumption.

The prints from Shapeways came out much better:

The basic Shapeways plastic doesn’t have any issues with overhanging parts, so they’re printed in one piece.  These ran about $15 each.  They won’t have to last long, as we’ll likely replace the stove soon anyway .

The STL files for the knobs are available on Thingiverse.