My eyes light up at anything with a sleek design, so you can bet they were as wide as golf balls when I saw that square tube knife by YouTube knife maker Koss:

YouTube video

Koss used 01 high carbon alloy steel (non-shrinking steel which hardens in oil) for the blade of his project. He started shaping it by cutting out a rectangle-shaped piece and using his belt sander to cut out the knife edge.

Shaping the Knife

square tube knife

Interestingly, he used the natural shape of the metal as a guide to making the knife. One edge of the rectangle was given a blade curve, while the opposite edge became the spine. The other two edges were filed down using the belt sander to thin the knife blade.

Heating and More Shaping

square tube knife

Once the knife was shaped, it was tossed into a kiln and quenched in oil to make it more malleable. After a couple of rounds of sanding, the knife was sharp enough to cut something.

Hiding With a Handle

square tube knife

To make the square tube knife look inconspicuous, Koss tried to make the exterior as ordinary as possible. He did this by using a piece of aluminum tube for the handle and the sheath. He must have taken the tube’s measurements into account before cutting the high carbon alloy steel because the tubes fit his knife perfectly.

He added a couple of Micarta caps to cover the open sides of the tubes before filling the handle with adhesive. Koss popped in the knife, making it both functional and beautiful.

square tube knife

Sadly, Koss wasn’t able to show off the cutting capabilities of his square tube knife. Nonetheless, it would undoubtedly work for general cutting purposes. If it fails to do so, a grindstone will quickly make the blade just as sharp as any.

On the other hand, it is hard to deny that the knife is indeed sleek, and those symmetrical edges on the handle make you want to fidget with it. That being said, this is definitely a knife worth keeping on your person!


Carlos wrestles gators, and by gators, we mean words. He also loves good design, good books, and good coffee.