This is a remix / mashup of two different things: the Parametric Knurled Nut Knob by John Sanford (drofnas) and the Thumbscrew with Open Hardware Logo by PuZZleDucK.
I am using it (as shown in the pictures above) as the X-axis belt tension adjustment knob for my set of improved Prusa i3 / P3Steel parts.
The M6 nut should be heated up before being embedded in its nut trap in the body of the knob.
OpenSCAD sources are included so the design can be further remixed.
Printed here in PLA with 30% infill, 0.2mm layer height, and 0.6mm walls and top/bottom layers.
Can be printed either way up, but I prefer the result when the Open Hardware logo is up, so I rotate the object by 180 degrees in the slicing software.
Heat up the M6 nut with a soldering iron then embed it in the nut trap in the body of the knob.