Kitchen Knives Set – Part 6: Honing Steels


The project is going into its final stage, so I should probably update you on the process some more. So today I am going to write about how the two honing steels were made. Lotsa of pictures follow.

First a choice of materials – two old semi-round files.

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They were already annealed and ready to go, so I ground them from a semi-round profile into a lenticular profile. That has of course made them a bit thinner and narrower, but not too much.

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The files came from annealing a bit bent, and after I have ground away the surfaces, they have bent some more. Not too much, but it was clearly visible. So I have straightened them a bit.

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Since they were still over 5 mm thick, the unbender would not be robust enough to cope. So I had to use a more primitive and more brute-force method as you can see in the picture. I did not manage to straighten them perfectly, but enough so it won’t affect the function negatively.

I wasn’t even attempting to polish these completely, it would be counterproductive.

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In fact, I have made longitudinal scratches with fine file over as much of the surface as I could manage before I got bored.

Next was hardening. I have put both steels into a pipe with carbonitriding mixture. I did not want to harden the tangs, so I have covered them in clay. Work that I could have spared myself from doing, as it turns out.

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The problem was, that I did not want to wait too long. The pipe was too big for me to let it simmer for several hours at about 500°C in the forge, so I have heated it to over 700°C for two hours with charcoal. And as I should have known, this temperature is too high for the clay in presence of natrium salts. The result – clay dissolved into the molten salt completely.

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Getting the steels out of the pipe was a bit difficult, I had to spill some of the salt onto the gravel. Next time I will be better prepared. Next time I also hopefully do not forget my safety glasses for this quench. Unlike normal quench, steel quenched from molten salt bath makes the water go boom. Not too much boom, but boom nevertheless.

I do not know if my reasoning is correct, but it was thus: the honing steel needs some very mild abrasive action. Carbonitriding the surface with longitudinal scratches and not very polished surfaces could provide that, but still, these knives have hardness around 62 HRC, so even carbonitrided steel won’t be much harder. But what is harder? Ferrous oxides. So I have decided to coat the steels with haematite.

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First I have prepared a bath of vinegar (some amount), salt (adequate), and hydrogen peroxide (splash a bit). Repeatedly dipping the blades and letting them dry has covered them in a black-brown mixture of ferrous oxides, hydroxides, and perhaps acetates.

How to convert this rust into a more stable form, i.e. haematite?

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Boiling for a few minutes and then wiping the steel with a dry paper towel. This gave both steels a blotchy, mean-looking surface. If I manage to sell these sets, I will have to write to the future owner about how to do this to renew the oxide layer after it gets worn down. Because I am convinced that it does give the steels some more abrasion. At least I think the steels definitively do work as intended.

Honing steels have more than one thing in common with daggers. One of those common things is the presence of a crossguard. Only unlike in a dagger, a crossguard from steel is in my opinion a bad idea, since people who are accustomed to honing the knife towards the hand (like myself) could accidentally hit the guard and ruin the blade. So I have decided to go with bone in one case and buffalo horn in another. Fitting the holes was a bit onerous, but that was mostly because the tangs were a bit awkward. If I were making these from new materials – which I intend to do in the future – it should be easier.

After grinding and polishing the two handguards, two handles and one buffalo-horn pommel came the last step – gluing it all together. I have decided against full-length tangs since they should not be necessary for something that is not supposed to be put under mechanical strain. I have only ground notches into the existing tangs and epoxy glue should hold it all together well enough.

First I had to prepare a gluing jig.

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The tip of the steel is inserted into a hole in a small rectangular piece of hardwood. Then I have wound a piece of string several times as you see in the picture so that it pushes the handle against the steel. After 4 loops on each side, I have tied the string to the wood, put it aside, and prepared the glue. For practical reasons I have used slow-curing epoxy, and that was a very wise decision.

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I had to be careful to not let the strings get tangled up, but it was not too difficult. What was a bit difficult was filling the hole in the handle with glue.

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This glue has the color and consistency of snot. It looks disgusting and it does not want to flow anywhere, except on your shoes and clothes. It refused to go into the hole and I had to poke it with bbq skewer several times to let the air escape and the glue sink. But after several minutes of intensively trying not to curse because I am filming myself doing this, I have managed to fill the holes with glue. Then I could insert the tang and press the whole assembly together to squeeze any excess glue out.

This is where the string and wooden block jig came into play.

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There are jigs for this on sale, and one could also build a more complicated one with screws and whatnot. But these simple ones worked like a charm,  I had no trouble whatsoever.

After inserting the assembled steel into the jig I have simply put two popsicle sticks between the strings on both sides making two Spanish windlasses that when tightened press the assembly together with great force. Two sides allowed me to adjust the force symmetrically and the popsicle sticks locked in place without a problem. They were also thin enough to give me feedback when the rope is tight enough so I could not over tighten it and snap it. All in all, I have expected this to go wrong in several ways, but instead, I have found a simple and usable solution into my knife-making repertoire for the future. The pieces of wood go from a trash pile into the jig pile forevah.

And to finish this post a picture you have seen in several contexts already – the thingies resting on a warm radiator, waiting for the epoxy to cure.

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Comments

  1. amts says

    Very, very cool. I love the way you invent solutions to problems — incidentally using and ‘recycling’ found objects — instead of just going out and buying something. Bravo!

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