The big button you slap on the top of my Slap Chop cracked after only a few weeks of using it, so I designed a replacement part that's much more solid, and is also much easier to reassemble (since it has a built-in cone guiding the spring around the rod into place).

Printing

The inside of the knob has a little flat part for the spring to hold against, which requires some support structure to print cleanly: the basic “knob.stl” includes a removable 0.4mm one-perimeter cylinder inside the knob for this purpose. The “no-support” version of the model is provided if you want to try an alternative support structure/orientation, or if your slicer has a more clever bridging strategy that would make this support unnecessary.

I printed this in PETG, with default infill: other materials like PLA would probably work just as well, though I'm not sure if they could take as much of a beating.

Source code

The OpenSCAD source for this model is available on GitHub.