I did not expect to get a commission this early. I am not quite there yet to be able to make a good quality knife in a reasonable time. I am confident I can get the “quality” part right, but time – definitively not. My original plan was to perfect my manufacturing process with the kitchen knives, which, if you remember, I have left this spring at a phase where the outlines of the blades were established, but nothing else.
But I need to work on both projects now because apart from the time I also need to use my resources – electricity, propane gas and charcoal – in a more economically savvy manner. That means hardening multiple blades in one go for example. And that means I have to establish the primary bevel grind on the commissioned knife as well as on the kitchen knives so I can harden and temper all those blades together.
But the whole point of the kitchen knife project was to develop a viable manufacturing process, and establishing the primary bevel was the part where I knew I have to develop and build a fixture first. You have seen my very first attempt. It did work, but not very time-effectively, I wasted about a minute each time I needed to flip or change the blade. That is a lot, considering that for the basic grind I need to go through five belts on both sides. It was clear I need some way to hold the blade steady, but being able to dismount and re-mount it quickly.
The second attempt was this.
The idea was that the hinge and two screws will allow me to set the tilt, and the knife-blank can go into the slot where it will be held by the levered screw. It did and did not work. That is, it worked for one knife and then it broke. The problem was moisture which caused the wood to deform and split. But even without that, fixing and releasing the blade was still not as easy as I would like it to be. I got an idea on how to improve this design, and I already bought the materials to try it out, but then I got sick and everything got put on hold for a few months as you know. All I could do was to think about it.
And then my parent’s hard drive died and I got the idea to use those strong neodymium magnets. But for that, I need first to develop a system on how to switch them on/off, and that needs more time than I can spare right now for fooling around. The customer is not in a hurry to get the knife – they know I still have my day job and that I can only do this in my spare time – but still I think I should not strain their patience. So I needed a fixture, fast.
Luckily I got an idea utilizing things that I already have – the first attempted fixture and a few cheap, weak magnets. There is a way to make weak magnets a lot stronger, at the cost of reach – by concentrating the magnetic field to one side with two slabs of iron/mild steel. It is also possible to make longer arrays with this system.
So I took six of those cheap magnets and cut nine pieces of mild steel exactly as long as the magnets, but a few mm wider. Then I covered a piece of steel with masking tape and glued the magnets and steel together into three blocks, each consisting of two magnets and three pieces of steel, with the magnets facing each other with the same pole. That means the magnets oppose each other in the middle of the array, forcing the magnetic field of each magnet to the side.
The masking tape has stopped the magnets from glueing onto the steel, and the steel was there to get nice alignment on the backside of the arrays. The frontside has the steel pieces overlap a bit, and the spaces were filled with epoxy and sawdust mixture.
Whilst the epoxy was curing, I took the first wooden fixture and attached a long strip of aluminum to it for the spine of the knife to rest against, and I chiseled out three spaces for the magnet arrays to be glued into. After the epoxy has cured I ground the front faces nice and flat and glued the arrays into the wooden block, again with using a piece of steel covered with masking tape to hold all three on one plane. I used a lot of fast curing epoxy that day, all the while completely forgetting to take pictures of the process. So the next picture is the finished fixture with a knife blank attached to it.
To get the tilt the fixture has four screws on the downside (up in the picture, not visible).
And the fixture works. The magnet arrays are strong enough, but not as strong as neodymium magnet arrays, so it is still possible to comfortably detach the blade by hand. It allows me to apply a lot more even pressure on the blank, for a longer time without cooling it because I do not burn my fingers (temperature not being of concern at this stage). There is still room for improvement – the aluminium stop is a bit too fat for kitchen knives, the screws for tilting do not provide stable enough support and they are a bit finicky to get right. But you can see it allows for making nice, flat and even grind.
Added bonus is, that after two hours of grinding not only did I do more work than before, but also my fingers hurt a lot less because the fixture gives my hands more material to hold onto. I am definitively going to use this a lot, and perhaps there will be other uses for this concept as well. I have an idea for sharpening gizmo in my head for about a year by now…