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  1. #11
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    Default Re: Just finished this

    Quote Originally Posted by Toxxyc View Post
    If you don't have access to furnaces and things, how would you harden the blade's steel then? Just heat it up in a fire until it loses magnetic properties and douse in oil?
    It depends on the type of steel. For stainless, it's better to use a professional service until you can get or make a proper heat treating furnace. For something like leaf springs (5160) or K460 (o1), heating until non-magnetic plus a few seconds for luck, then quenching in warm canola oil is all that's needed.

    I say canola or vegetable oil because it smells much, much better than trying motor oil or whatever concoctions you may find on the internet. I also gave the AISI designations because generally there is more information on the American sites, and they use different names for the steels.

    A suitable heat treating forge can be made with as little as 3 firebricks (Contractor counter at builder's warehouse is where I got mine), a piece of mild steel pipe and a hair dryer. Bricks in a u-shape contain the heat, bury one end of the pipe in charcoal and duct tape the hair dryer to the other end. Should be more than enough heat for simple or low alloy steels.

  2. #12
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    Default Re: Just finished this

    I take it the idea of the heat-and-quench, specifically in oils, is to introduce carbon to the steel to seriously harden it (as well as to cool it rapidly and therefore get the metal's structure a specific way), but how about using a method like samurai swords were made, for example to coat certain parts of the blade different thicknesses with whatever is available before quenching? This was done to get the cutting surface harder than the "bulk" of the blade, making it more durable AFAIK. Anyone ever try something like that? I mean, at R100 for a blank, it's definitely worth a try.

  3. #13
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    Default Re: Just finished this

    @Darren - very very well done! really looking great!
    @Toxxyc - get started. yes, the KMTS prices are very reasonable for a blank and the additional bits are not bad either!

  4. #14
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    Default Re: Just finished this

    Quote Originally Posted by Toxxyc View Post
    I take it the idea of the heat-and-quench, specifically in oils, is to introduce carbon to the steel to seriously harden it (as well as to cool it rapidly and therefore get the metal's structure a specific way), but how about using a method like samurai swords were made, for example to coat certain parts of the blade different thicknesses with whatever is available before quenching? This was done to get the cutting surface harder than the "bulk" of the blade, making it more durable AFAIK. Anyone ever try something like that? I mean, at R100 for a blank, it's definitely worth a try.
    Heating the blade and quenching doesn't add carbon, the carbon has to be in the steel as manufactured. In fact if you over heat the steel you can lose carbon making it a less effective blade. I think what you are referring to with Japanese swords with the coating, they normally used a softer steel for the main body of the blade and had a high carbon steel for the edge. This gives you an edge that keeps sharp, but the softer steel in the spine gives flexibility. Nowadays we can create a fake Hamon (pronounced Hamoon) which show a wavy line down the blade like a Japanese sword. It is simply done by coating the blade with a refractory cement (gungum also works apparently), The edge is left clean and this has a similar effect by not hardening the spine as much as the edge.
    One of the things that I really like about knife making is you are only limited by your imagination. Check out Bertie Rietveld knives! That man is a genius.

  5. #15
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    Default Re: Just finished this

    To keep a soft spine and a hard cutting surface, you can either differential heat treat or make your own San Mai blade. Info from wikipedia

    Differential heat treatment (also called selective heat treatment or local heat treatment) is a technique used during heat treating to harden or soften certain areas of a steel object, creating a difference in hardness between these areas. There are many techniques for creating a difference in properties, but most can be defined as either differential hardening or differential tempering. These were common heat treating techniques used historically in Europe and Asia, with possibly the most widely known example being from Japanese swordsmithing. Some modern varieties were developed in the twentieth century as metallurgical knowledge and technology rapidly increased.

    San Mai, in the context of metal blade construction/metalwork, refers to a knife, blade or sword that has the hard steel hagane forming the blade's edge, and the iron/stainless forming a jacket on both sides. It is also the term used to refer to the technique used to create these blades.

  6. #16
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    Default Re: Just finished this

    Quote Originally Posted by Toxxyc View Post
    I take it the idea of the heat-and-quench, specifically in oils, is to introduce carbon to the steel to seriously harden it (as well as to cool it rapidly and therefore get the metal's structure a specific way), but how about using a method like samurai swords were made, for example to coat certain parts of the blade different thicknesses with whatever is available before quenching? This was done to get the cutting surface harder than the "bulk" of the blade, making it more durable AFAIK. Anyone ever try something like that? I mean, at R100 for a blank, it's definitely worth a try.
    Pretty much what Darren said regarding the Hamon. Samurai swords are an entirely different ballgame, and involve some pretty complex metallurgy. They are constructed through a method known as San Mai, which entails forge welding different types of steel together. In this case, high carbon in the middle for a sharp, hard cuttin edge and low carbon or medium carbon at the spine and on the sides for flexibility and toughness.

    During heat treatment, there are a number of processes occurring in the steel. Effectively when the steel is soft, the carbon forms a spherical Chrystal structure. This makes it very easy to machine, but useless at holding an edge.

    As the steel heats up, the carbon atoms rearrange themselves into a more angular structure which allows the blade to take and hold an edge. The reason for the quench is to freeze the steel in this structure by rapidly decreasing the temperature. If done correctly, this results in a hard steel which can take and hold a sharp edge very well.

    If done too fast, the steel will contract more quickly than the Chrystal lattice can take, and the blade cracks or warps.

    If done too slowly, the steel returns to a more spherical structure. The reason for the clay or refractory cement is to allow the edge to retain the angular structure, while the spine returns to the spherical structure. The reason why the line appears is that there is some really funky metallurgy going on at the point where these structures intersect. The different structures all react differently when etched with acid, and the intersection will usually become darker than either the blade or the spine. It's worth noting that this depends heavily on the alloy used, as any "deep hardening" properties make a Hamon or fake Hamon almost impossible.

    Differential heat treatment in itself is not too difficult and is often recommended for larger blades which need to be tough and hold an edge, such as that required for the American bladesmith society's journeyman tests. Installing a plate which limits how deeply the knife is submerged during the quench should give the desired effect, ie since only the edge is submerged, only the edge will harden while the spine stays soft and tough.

    There have literally been books written about heat treatment. On top of the YouTube suggestion, I suggest that you join a few knife related forums. British blades seems to be very popular with South African knife makers. Unfortunately sablade is closed to new posts, but there are some great examples of what SA knife makers are capable of.

  7. #17
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    Default Re: Just finished this

    Very nicely done.

    Sent from my SM-G900F

  8. #18
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    Default Re: Just finished this

    Quote Originally Posted by pigeonpie View Post
    Pretty much what Darren said regarding the Hamon. Samurai swords are an entirely different ballgame, and involve some pretty complex metallurgy. They are constructed through a method known as San Mai, which entails forge welding different types of steel together. In this case, high carbon in the middle for a sharp, hard cuttin edge and low carbon or medium carbon at the spine and on the sides for flexibility and toughness.

    During heat treatment, there are a number of processes occurring in the steel. Effectively when the steel is soft, the carbon forms a spherical Chrystal structure. This makes it very easy to machine, but useless at holding an edge.

    As the steel heats up, the carbon atoms rearrange themselves into a more angular structure which allows the blade to take and hold an edge. The reason for the quench is to freeze the steel in this structure by rapidly decreasing the temperature. If done correctly, this results in a hard steel which can take and hold a sharp edge very well.

    If done too fast, the steel will contract more quickly than the Chrystal lattice can take, and the blade cracks or warps.

    If done too slowly, the steel returns to a more spherical structure. The reason for the clay or refractory cement is to allow the edge to retain the angular structure, while the spine returns to the spherical structure. The reason why the line appears is that there is some really funky metallurgy going on at the point where these structures intersect. The different structures all react differently when etched with acid, and the intersection will usually become darker than either the blade or the spine. It's worth noting that this depends heavily on the alloy used, as any "deep hardening" properties make a Hamon or fake Hamon almost impossible.

    Differential heat treatment in itself is not too difficult and is often recommended for larger blades which need to be tough and hold an edge, such as that required for the American bladesmith society's journeyman tests. Installing a plate which limits how deeply the knife is submerged during the quench should give the desired effect, ie since only the edge is submerged, only the edge will harden while the spine stays soft and tough.

    There have literally been books written about heat treatment. On top of the YouTube suggestion, I suggest that you join a few knife related forums. British blades seems to be very popular with South African knife makers. Unfortunately sablade is closed to new posts, but there are some great examples of what SA knife makers are capable of.
    I think I should whip out my old Material Science textbook and read up on the crystalline structures and temperatures of different steels... :P

  9. #19
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    Default Re: Just finished this

    Quote Originally Posted by Toxxyc View Post
    I think I should whip out my old Material Science textbook and read up on the crystalline structures and temperatures of different steels... :P
    Great idea! I would also suggest do a course, plenty of guys your side that do courses. I'll be doing one this month, that is why I am selling this knife for some extra funds!

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