I liked the idea of the EAB knife I remixed, but as a print-in-place design the tolerances were pretty floppy. So I ended up redesigning the mechanism and making a few other minor changes while I was at it. 

I went to a non-print-in-place design because print-in-place requires fairly significant tolerances that result in the floppiness of the original model. Instead I have a screw retention for the opening axle. I also redesigned the latch with a ramp. As a result this design is a detent action rather than a push-to-release; while the knife stays open and does not jiggle, it will close easily with a firm push of the blade holder, no push of the latch mechanism required.

Mine is Polymax PC but I believe it should work in a good quality PETG as well. 

Assemble using 2x M3-8mm socket-head screws and 2x M3 hex nuts. The axle screw should be loose so that it doesn't add drag; the screw is only to hold the two sides in position relative to each other and over tightening just makes it difficult to open and close. The blade screw should be tightened sufficiently to hold the blade securely. Use a longer M3 screw to draw the nuts into the plastic before installing the 8mm screws. You will need to open and close it a number of times to smooth the motion elements before it opens and closes easily. 

Supports are not included in this model, and are needed for the clip, axle, and latching elements. I have included a Prusaslicer model with the supports already painted. 

0.6mm nozzle recommended. 

(revised version - may be a bit more durable, and the action definitely feels better when printed with petg vs the original version)

(addition - I added another varianty of the body that thickens the hinge part of the latch to make it stiffer, which makes it more like the original push-to-release action. May not work great with PETG, the fit is fine but I keep breaking my test models ;)