Interlock mechanism for winder spool gear/spindle axles - Filament Spool Rewinder

I tested several different main spindles for the awesome filament spool rewinder project.  The main issue I found with these is that they put one flat surface onto another and rely on axial pressure to prevent slipping.  Inserts work better, yet still rely on a relatively small surface area to transfer all the rotational torque, I spun a few of those out of the spindle before designing an alternate solution.

I created an interlocking mechanism between the gear and spindle pieces that locks them together and spreads out the rotational torque across more surface area.  Add as a part to Bearing Spindle Part1 and a negative volume to Bearing Spindle Part2, relative positions for both are in the photos section.

I printed in ABS, 0.2mm layer height, the parts fit well together.  Four wall loops, 25% Gyroid infill may not be needed, this is my standard and I did not test other parameters.  My printers are fairly well calibrated, if yours are not as accurate, you may need to do some X-Y contour compensation.  The M5 screw also pushes the posts out a bit, further enhancing the positive lock.