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The purpose of heat treating is to bring steel to a hardened state. The correct hardness depends on the application of the steel being treated. Knives need to be hard enough to hold an sharp edge through continuous mechanical abrasion, yet be soft (flexible) enough to stand up to forceful use without breaking.

Equipment and tools:
- Visegrip pliers or tongs
- small forge or charcoal fire of sufficient heat (search for forge or smelting instructables)
- fire proof quench container with lid (I used an old cookie tin)
- quenching medium such as used motor oil
- BC fire extinguisher (the kind that puts out grease and oil fires)
- Heat resistant gloves and face shield.
- kitchen oven
- fireproof material for regulator block (I used aluminum tube)

Materials:
- one mild or high carbon steel knife blank (forged or stock removal)

The quenching method I decided to use for this knife was the “edge quench”. I learned this method from $50 Knife Shop by Wayne Goddard. Instead of dropping the heated knife into the quenching medium tip first, submerging the entire knife, the edge quench involves submerging one third to one half of the blade's width (cutting edge first) into the quenching medium. A regulator block is used to hold the blade at the correct depth. The quenching medium I used was old motor oil. After the blade has been quenched, its hardness is still not suitable for usage. In its hard and brittle state, the quenched blade will shatter like glass if dropped, it must be tempered before it is put to use. Tempering involves heating the blade to a non-critical temperature (350 – 450 F) to slightly soften the steel (I used a kitchen oven). A tempered blade will hold a sharp edge and still retain strength and flexibility.

Step 1: Surface and edge preparation

The heat treating method is the same for knives made from forging, or stock removal. Whatever method you used,the final bevel should be on the blade and the surface should be brought to the desired finish. This was one of my first forged blades and I found the hammer markings appealing, so I did not polish the blade to a mirror shine, but I used a file to cut the bevel and a rough stone (100 – 200 grit) to get it fairly smooth, and as even as possible. Remember, once it is hardened, it will be much more difficult to remove material via filing and sanding. The edge is the thinnest part of the blade, and therefore more prone to cracking during the quench. Use a strip of 150 grit sand paper to dull the edge and reduce the chance of cracks or warping in the edge.

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I hear treated some blades last night and they came out COVERED in all kinds of crud, would you have any useful advice for me? Lol, I'm desperate lol
Put wd40 on it and scrub it off with sandpaper ij the direction that you want your grain
<p>This has to do with the metal you are using specifically. At higher temperatures, metal, especially carbon steel, oxidizes at higher rates. With the specific &quot;A&quot; number of your metal, it seems to have few deoxidizers, meaning it will oxidize in the air quicker than if it had increased levels of Silicon, Aluminum, or Manganese. Try a different metal, and spend a little extra to get some good stuff if you want solid results.</p>
<p>I just heat treated and tempered my blade to brown/straw as you showed here, but the edge was still too fragile and the tip broke. So my question is: Is possible to heat it too hot before quenching? Blade was almost bright orange in the daylight when I quenched it. And I&acute;m 100% sure I did tempering correctly. Please help me so I can avoid this in the future.</p>
<p>It's really hard to see the color in daylight - our forge is pretty dim so we can see it pretty well. But even then, I don't usually trust my eyes for the quench. To make sure it's ready, you can get a magnet and hold the blade near it. If it's not attracted to the magnet, you've reached the right temperature. Just be careful - if any part of you gets between the blade and magnet, you can get a red hot knife stuck to your finger!</p>
<p>Quenching should be done when the steel reaches a bright red colour, 800-900 fahrenheit. Forging and shaping the steal is done at a bright yellow/orange colour, 1700-2100 fahrenheit. quenching at temperatures over 800-900 degrees can result in a brittle blade and/or your blade could warp or crack.</p>
<p>Quenching and Tempering refer to two specific heat treating processes. It seems like you may not have tempered 100% correctly. Quenching is much easier, and only requires that the metal reach Austenizing temperatures and then is rapidly cooled. Tempering on the other hand, is much more specific. It requires a quenched material, quenching being as described above, be taken to temperatures below the first transformation temperature of that specific alloy (normally 1100-1300) and held for 1 hour per inch of material. It is then cooled in the furnace, dropping temperatures roughly 400 degrees per hour (again, depending on the alloy) down to 700 or 800 degrees (again, depending on the alloy) and then air cooled. Higher alloys require controlled cooling to much cooler temperatures, as they commonly are more suseptible to diffusion (oxidation basically) at lower temperatures. Hope this helped. I fear they use their heat treating process labels loosely around here.</p>
<p>Just so you know, quenching and tempering have little to no effect on mild steel. You will still see the color appear from the tempering process, but there isn't enough carbon present for the metal to harden properly. As for the material you've been using, in my experience, anything that cuts is usually at least medium steel - so you're good there. Lawn mower blades are highly prized junk steel! If you want to go all out (affordably) get some leaf spring from a junkyard. Most of the swords I've made started as leaf or coil spring. It's good stuff. Thanks for the instructable!</p>
<p>I have quite a few knives I would like to have tempered so that they cut better. You mentioned that when tempering a metal blade, it should be between 350-450 degrees Fahrenheit. At what point does the metal start to melt? http://www.pacmet.com/index.php?h=capabilitiesandservices</p>
<p>This is actually misleading and has to do with their use of &quot;Tempering&quot;. Tempering is a specific heat treating process that takes quenched steel, with &quot;quenched&quot; steel being metal that has been taken to Austenizing temperatures, roughly 1650 degrees Fahrenheit, and then rapidly cooled. Once that has been accomplished, the metal is then taken to temperatures below the first transformation temperature, roughly 1100-1300 for 1 hour per inch of material. IE 1&quot; material would be kept at that temperature for 1 hour. It is then furnace cooled, dropping roughly 400 degrees per hour to 700 or 800 degrees and then air cooled. Varying the temperatures, while obeying the two critical temperatures and time constraints, should give you an ideal &quot;temper&quot;.</p>
<p>These instructions are great! Now if only I follow them.</p>
<p>I have never heard about having to heat the oil before quenching the work piece, but it does make sense I suppose. I found in all my years of metallurgy experience used diesel oil works the best and doesn't have to be warmed prior to using due to multitude of additives and relatively thin viscosity once used. Basically the purpose of this is merely to cool the metal at a slower rate to prevent stressing the metal to the point of fracture, and it also replenishes the carbon content in the steel allowing it to hold a sharp edge. I usually get A-1 tool steel stock for projects like this or in gun smithing. There is also a cool little color chart BTW a great source for high carbon steel suitable for knife making is at saw shops, or any place that deals with replacing the blades of wood chippers, industrial sheet metal shears, old school paper cutting boards. etc. </p>
*heat treated lol
*heat treated lol
ok i have been doing about 1 1/2 on google and youtube and made my first 2 knifes out of a lawnmower blade no tampering no hardening and holds an edge pretty desent but my main question is is there differnt temps for different types of carbon steels
<p>Absolutely! A lot of it is trial and error, but I suggest looking up a steel heat-treating chart.</p>
you say that in its quenched state it is still brittle. but with the blades i have made after i quenched them they were still very strong.
You might need to use a faster oil or a brine solution for your type of steel. What kind of steel are you using? I often have the same result with steels that only harden on the surface, the core remains tough and supports the brittle 'sheath', but this only happens with some steels that I use. Remember, the quicker you quench without cracking, the finer the grain structure and the tougher the blade will be at a given hardness. Good luck with your blades.
my first blades were made from low-mid steel. (dresser drawer sliding bracket, and a shelving bracket.) the first one (my only instructable) does not bend easily and does not hold a great edge. (like i said low-mid steel) however it works like a child sized machete. the second one from a shelving bracket bends a little easy, but hold its edge and can be bent some distance before diffuclty is hit. and can be bent back without weakining. <br> <br>only first blades cause im still working on my 3rd one (sword). the knives i could finish in 4-5 hours in my coal/wood fire pit. brick, wood or rock was used as anvil (all broke hehe) but i need anvil or anvil like thing for sword. last time i use a block of wood as one and i split it in half.(freshly cut too, very hard.)
If you can get a hold of a piece of old rail road track or one of those antique irons you should be able to use that as an anvil without it breaking, I've used a railroad track for mine, but since it's covered in divots and dents from people doing the same to it before I had it, I use a smaller iron as a &quot;finishing&quot; anvil to get the final shape. Those will be easier to get if you live in an area with ranches or farms though, they may be harder to find in cities for free. As for the steel, I'd have to say that you'd have better luck making durable knives from a higher carbon steel, I've found a bunch of old files from my family farm and I've figured out a pretty good heat treat on Tool Shop brand files (really cheap where I get them) to where I can chop through several oak boards and still have them razor sharp. I'm trying to get some higher quality steel online though. NJ Steel Baron has some good prices and pretty good quality too, I'll hopefully be ordering some 52100 steel from them, I've seen that steel chop through hardened bolts so that's my new goal as a knifemaker. That's a pretty cool knife you make in your instructable, good luck with any other knives or swords you make. If you have any questions don't hesitate to ask.
Nice, thanks for the info. I needed it. Here's one i just finished
Handy looking blade Semper Fi. Details on the octagonal pins please?
There small bolts from a pop up canopy that got destroyed in a storm. Just countersunk and ground flush.
Nice. Are the ends on the opposite side peened over? Did you heat treat it? The coloration on the bevel suggests it took some thermal abuse.
Thanks, they are flush. no heat treating, thats why i was glad to see your instructable. I think its just a shadow from me taking the pic. I'm not sure what grade of steel this is, i got it at a rock quarry i worked at year ago. But i do know its really hard (Hard). lol it holds its shine and edge very well. Can't wait to see some more of your creations.
The professionality of your work is very inspiring.<br>I also saw your blog, and it says you created your instructables account only a few days ago.<br><br>Do you forge metal by profession, or just a hobby?
Thank you for visiting my blog! Although it is not making me money yet, the reward in the craft itself is enormous.
Great instrucatable, Do you mind if put a link to your instructable into my instructable of how to make a bowie?
Sure you can. I saw your &quot;riveted sword of the monkey&quot; instructable, looked like there was fair amount of forge work involved. I'm currently using the gas forged pictured above to draw out a pair of hunting knives from a file, trying to improve my blacksmithing skills.
Nice! <br><br>I don't take much pride in my riveted sword of the monkey any more, haha I've been working on a new katana. that's close enough to almost perfect. the only problem is is the the blade is too thin.
I have never made a knife and doubt I will ever get around to making one. Your Instructable is very interesting and I appreciate all of the detail.
Thank you Phil B.

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