Zippy Balisong Inspired Balisong(M3)

Tolerances basically don't exist. You'll need decent calibration. Alternatively, just make the blade a little thinner in slicer, or the bushings a little taller. 

The holes in the blade/handles fit 6x3mm magnets. For balance, I'd print at 100% infill, then add all 5 magnets. Feels nice to me(handle biased). 100% infill also makes it sound like wood, which is cool. 

Uses M3 screws(12mm) and nuts. 

If the handles start to clack/hit each other, then check your bushings. In my experience, the handles clacking means the bushings wore out and I need to reprint. I can feel the handles and they slide around in the bushings. After reprinting, they don't and the handles don't clack.