My first folding knife model. The spring arrested folding mechanism works like on Swiss Army Knives. The blade is held in the opened or respectively closed position by a strong steel spring that blends into the spine of the handle. The whole mechanism lives inside a strong steel frame. There are no screws, everything is glued up with epoxy. The liners are laminated grey paper and a layer of pearwood veneer to give it a lighter two-color tone. in the closed position, the edge of the blade does not touch any inner parts of the knife to keep it sharp. The handle scales are made out of a nice red Padouk wood.Continue reading “Folder: Spring Folder”
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.
I have recently finished more kitchen knives. I worked on another Japan-style Furutsu petty knife and a Chinese chef’s knife.
I used 2 mm O1 steel for these knives as this gives a good mix of stability, flexibility and thin enough to be highly sharpened. O1 is my favorite steel to work with.
On my last order of handle material, I changed the supplier and checked out some of his materials. I found that he offered bamboo handle scales and as I already planned to do Asian-style knives I found them to fit perfectly and got two sets. The bamboo is not a solid block but more layered or stacked. I still like it a lot.
My first tries to add a Hamon
I always try to learn something new – this time I wanted to experiment with creating selective hardness in the blades and a Hamon. A Hamon is a wavy line between the hardened part of the blade – the cutting edge – and the spine of the blade, where the steel stays softer. The advantage is, that the hardened blade is supported by a softer part of the blade which results in a more stable knife – and to be honest: it looks just super cool.
To create the Hamon I prepared the blades as usual and then I created a mix of ash and clay. The recipe for the exact mixtures is a secret that is passed from generation to generation in our family. The clay is left to dry. Then the blade is heated together with the clay mantle and hardened in the oil.
After hardening the clay is removed and the blade is tempered and then hand sanded to the desired grit and then etched in ferric chloride, then sanded again. I repeated the etching and sanding process multiple times to reach the desired look.
For my first try I am very happy with the result. Must be due to the secret clay recipe of our family 🙂
I work on my own in my tiny workshop, that is what I usually do. But when a friend of mine called and told me that he knows somebody who would love to learn how to make a knife, I thought: why not give it a try. I had no idea what to charge for that, as I wouldn’t do it for the money anyway. So I just said a bit more than the material for a knife would cost.
So I met Arne – an eighteen-year-old guy, polite, friendly, and respectful – and very eager to learn the skills needed to make a knife. And what matters most: the ability to listen and learn.
He wanted to do a Santoku-style kitchen knife, similar to the chef’s knife I made. But he absolutely wanted to do a hidden tang knife – no matter how much I said that this would mean a lot more and complicated work for his first knife. But as he wants to give it a try we absolutely followed his decision.
We drafted his blade on a piece of paper on his first visit and I just added some tips on ergonomics and basic needs of a good cutting blade. Then I asked him to transfer that drawing onto the computer.
On his next visit I helped him modify some details on the computer, printed out his design and he transferred the cutout paper stencil to the 2 mm O1 steel.
Then we started with the first “big machinery” ok, just my handy little angle grinder – not so big machinery. Arne cut out the steel blade while I showed him some tricks and tweaks on how to get convex and concave cuts done right.
I let him do all the steps himself, only the ones that had the potential to ruin the knife I just showed him how I do it.
For the handle material he got some nice cherry wood and for the front plate (guard/bolster part) I had a nice brass and paper micarta piece left from a previous project. We tried a new technique to slot the handle for the hidden tang: We drilled a hole into the handle and only had the bolster with a tight-fitting slot around the blade. The hole was filled up with epoxy during assembly and the plate serves as a nice-looking cap.
The last thing to do was shaping the handle roughly with the band saw then going through rough grinding and finally hand sanding the wood into shape. The cherry wood is nice to hand sand to a satin shiny finish and the last step was to treat the handle well with Linseed oil varnish.
Arne did really good and the final product looks awesome. He can be really proud of his work and the knife which is a present for his father.
The first Tigershark knife I made might be the knife I learned the most from. I tried to do the final surface finish only on the belt grinder and failed miserably. The scratch pattern I got was way too uneven. Additionally, I etched the blade too early and ended with a partially ground out marking.
I used the belt grinder to put the secondary bevel on the blade as the first step of sharpening – I usually did that with diamond sharpeners by hand. The ultra-fine grit belt worked pretty well. It also was my first blade I sharpened with a leather strap and polish paste. That thing is razor-sharp now.
I always thought about if I want to sell the knife. I think it is one of my most beautiful designs with a nice handle and in the end, it is also a very practical knife. It has its small flaws and so it is still here and I am not sure if I want to keep it for me.
Then I got an order for a knife and suggested this model to my customer and friend. So I got the chance to start from scratch, make another Tigershark knife, and improve. This time I went for a high mirror polish with a mix of scratch pattern finish.
And then – the name-giving handle material serpent wood (with its tiger-like stripes) was out of stock at my usual shops. I waited a bit if it would be back in stock, but when it took too long, I went on to search for other suppliers and found one. I took the chance and also ordered some bamboo for two Asian style kitchen knives (more on that in a later post).
The making of the knife took me a pretty long time with lots of interruptions and private life issues which took me off my progress path. But I came back in my holidays, finished the blade and I am pretty happy with the results.
Next and last step will be making of the leather sheath.
I built a new burner for my water tank forge. The first one I built had serious airflow problems and with too much gas it tended to blow out its own flame. So the generated heat was limited.
With my new welder, I was able to rebuild the whole cap. This type of burner is called a Venturi Burner. The gas flow from the nozzle pulls the air through a pipe by the sheer velocity of the movement. The air is not accelerated by an electrical fan or something, it is pushed into the pipe by atmospheric pressure. The mixture of air and gas moves fast enough to flow and mix in the pipe but the flame can not go back into the pipe.
These burners actually rely on two principles: the Bernoulli Principle and the Venturi effect.
An increase in velocity of a moving fluid results in simultaneous decrease in its pressure (and visa versa)Bernoulli Principle
The result is that the velocity of the gas leads to a lower pressure of the gas (this is what the Bernoulli Principle says) and so the surrounding air (and so the oxygen) at atmospheric pressure is ‘entrained’ into the low-pressure gas flow to even out the difference of pressure, this is the Venturi Effect.
I bought some plumbing pipes made of iron and used a wire brush wheel on my angle grinder and a scraping disc to remove the zinc from the surface. Zinc can lead to health issues if heated and the gases are breathed in.
First I just held the cap near the top funnel and lit the burner to find the right distance and the right gap for the air intake. Then I welded the two parts together. The top cap is the former tip of a usual gas burner used on roofs. I just cut int into the right shape.
Yes I know it is not beautiful but a huge improvement that ads a lot of power to my forge and the flame is more stable at higher settings.
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As I wrote some times ago I like to learn new things, combine the techniques I learned to something new, and expand my skills. One thing on my bucket list was to buy a welding machine and learn to weld. Probably because I saw my dad try his best with his not-so-good arc welding transformer when I was a child and still I am fascinated.
I looked up different machines, not too expensive for just getting my feet wet, with good reviews, and most importantly it should be as flexible as possible when it comes to welding techniques. I ended up having a look at Stahlwerk Schweißgeräte [unpaid advertising]. I was thinking about to get their MIG 200 amps machine as it was able to do Mig/Mag, arc welding and flux-cored welding. Unfortunately, it was not on stock for a long time on their site and on Amazon. I even got a welding automatic helmet and welding gloves for Christmas long before I got the machine itself.
So last week I did it and hit the “buy now” button as a pre-order. I had decided that for my needs 175 amps would be sufficient and bought the machine. The day the parcel service announced the package I kept hitting the reload on the parcel tracking page, nervous like a kid on Christmas Eve. Meanwhile, the tracking page even got a 500 server error message but fortunately, it wasn’t me. They where just launching a new page 🙂
I tried to weld some beads onto some scrap metal and oh boy times have changed. It was so easy to ignite the electrode and or the flux-cored wire. No way you can compare that to the old transformer I got in my garage, the old welding machine of my dad. In the end, I had the best results with simple arc welding electrodes.
In the above video you see my son trying out my new machine.
This is the second built of my Kukri III model that was ordered right when I showed around my first Kukri III. The “III” is the number of the base model not the number of the built. The handle shape is a bit different and the liners are made out of felt, not paper Micarta.Continue reading “Kukri / Khukuri: Kukri III #2”