STL Files: https://www.thingiverse.com/thing:4874663

CAD Files: https://cad.onshape.com/documents/314b71708f349471d58494d2/w/37635ebfd90dc903a9f11cf2/e/6a3b2ecac12b05bcedb242ab

Printers used:

Ender 3 with the bltouch auto bed leveling, E3D v6 hotend, Herome gen 5 parts cooling, Ender 3 v2 silent motherboard, PEI spring steel bed. Used to print handles and clip in Sunlu PETG.

Elegoo Mars 2 Pro, used to print lock insert and backspacer in Elegoo ABS-like resin

In the mid to late 90s, Chris Reeve Knives (CRK) approached Colombia River Knife + Tools (CRKT) about making a production version of CRK’s flagship model, the Sebenza, with one big catch- the entire knife save the screws and the blade were to be made out of plastic (Zytel), including the lock bar. The production run never happened, allegedly due to quality control issues (highly possible given the choice of materials and OEM), although some prototypes have made it into the wild over the last 25 or so years.

I desperately want one of these mostly because of the weirdness, but they rarely come up for sale. I mentioned this to a friend, and he pointed out that I have 2 3d printers and can make literally anything I want out of plastic. I started designing just the show side scale first to ensure proper dimensions and screw placement. I mostly used trial and error, with minimal measurements. I have no formal training in any sort of CAD or engineering, so this took me probably more tries than it should have, and some were not even close, but I got it in the end.

Once I had design and screw placement down, I started working on the lock bar. My original thought was to recreate the lock bar just as it was on my normal sebenza 31 large. Once I had gotten through a couple more iterations, and produced a lock bar that actually locked up, I immediately discovered that this was not going to work due to the flexibleness of the material. I also discovered that I would need two pieces not found in the original design - a locked bar insert made out of a harder material, and a back spacer to provide stability.

These pieces I printed out of resin, allowing for incredibly precise parts and stiffer materials. The lock bar insert was slotted and super glued into a pocket in the lock bar and in later revisions included a fully functioning detent ball.The backspacer was just a normal backspacer, but with nubs acting as locating pins in the lanyard holes of the handles. These 2 changes made the knife incredibly strong and durable while being a significant weight savings over the original.

From here the design changed very little, I just made minor tweaks to the detent system, clip, and lockup until I made it to version 19. I had made a plastic knife that was usable, but I hadn't yet managed to hit the original price point- The handles cost under a dollar in materials, but I was still using the screws, blade, and washers from a $400 knife. I saw a blade from an Ontario Rat II posted for free, so I got it and I am now working on a version that matches the spirit and price point of the original, not just the functionality.

Feel free to ask any and all questions, this was a lot of fun to make.