I also hopped on the 3D printed gravity knife craze, I just designed mine with a slightly different approach.

The handle is slightly redesigned version of the beautiful Carrot Gravity Toy Knife remix made by Chris Klepel. 

Have you noticed the subtle stylized letters I added to the sides? If not, it's still OK… ;)

Instructions

Printing

Print all parts as they are orineted in the project file. Use a lower layer height for the screws and the blade for finer treads, 0.15 worked just fine for me. Use supports on the inner half of the handle and use 100% solid infill for the blade to give it a little bit more weight.

I've printed mine using Prusamnet Galaxy Black PLA, Fiberology PLA Mineral Marble and Fillamentum PLA Mellon Yellow. I think they work together pretty well.

Assembly

Chris suggests the use of a tap and die set on the treads. Since my blade is printed horizontally I figured all I had to do is driving an M5 screw into the handle to smooth out the treads. Try not to overtighten the printed screws because they will definitely break.

Happy pranking… I mean printing! ;)