I am working on my first folding knife model. And to make the challenge complete I am trying to build a spring folder where a spring holds the blade in the opened or closed position (like the swiss army knives are made).
The most complicated part is, that all pieces have to fit together very precisely. The spring should not be too strong nor so weak, that the blade is able to wiggle around. This would also be a safety issue. Nobody wants to have a super sharp knife that could open while in the pocket. If the spring is too strong the risk is to slip when you try to close the knife and too much force is needed.
The axis and the connection points have to be set up very precisely. I feel like a clockmaker with fine files and sandpaper, tidying the friction parts up and even polishing them, so they do not scratch in the movement.
I had to experiment with the spring part. It is spacer and spring in one piece and I built it in a way, that the edge of the blade does not touch any internal parts of the handle when closed, so it remains sharp and smooth.
I had to experiment with the heat treatment for springs. I did not find good information on how to do this correctly. The first one was still too brittle and I snapped it and had to build a new one from scratch. When the steel is too soft it just bends and stays in that position. The spring loses all strength after opening and closing the knife after three or four times. In the end, I had a good resistance in the spring and it returns back to position every time.
The liner is a mixed material self-made Micarta. It consists of laminated gray paper and a layer of pear veneer. As all layers are drenched in laminating epoxy it is a waterproof and very stable material mix with a nice optical effect.
For the handle, I chose Padouk wood, a very nice and easy to work with material. It has good material properties and a coarse porous texture – The only thing was that it covered my whole workshop with a red layer of dust.
The etching says “spring folder” but the font I chose did not come out as expected, so next time I will choose a better-to-read font.
Another first-time was the use of my new polishing machine. That thing is kind of scary with the high speed and power. But it gets the polishing job done very nicely and it is so much more convenient instead of using a polishing wheel on my drill stand.
I am very happy with the results of my first ever made folding knife. I learned a lot – like always – and I can improve on that experiences for the next models.