A colleague owned an old Curta calculator with a broken handle.
So I designed and printed an replacement one for him.

The handle is designed in OpenSCAD, the knob is made with "Parametric Knurled Nut Knob"
http://www.thingiverse.com/thing:439239.

The knob is mounted with a M3 screw and 2 washers to make it rotating on the handle.
The handle is fixed with the original tiny bolt onto the Curtas axis.