Matinum

Taking Charge of Your Health


Hi everyone! Aaron from Gough custom here.
I’m going to show you today how to heat-treat an O1 tool-steel knife in your own shop, with
just a few simple tools. The very first thing you’ll need is quench
oil. The quench oil is what you put the blade into when it’s been heated up to red hot to
cool it down fast and make the blade harden. In this case we’re just using vegetable oil,
which is cheap and easily available and works very well. The next thing you’re going to need is a pair
of tongs to hold the hot steel. I use these big vise-grips, they were quite cheap. I think
they were only about $6 or $7 and they work quite well. If you can find blacksmith’s tongs then that’s
great but they’re not necessary as something like this works well. The offset head keeps
your hand out of the path of any possible flame from when you’re quenching the steel
in the oil. The next thing you need is a container to
hold your quenching oil. This is actually a small wine-bucket that I got from a kitchen
supply place. Kitchen supply places are great for this kind of thing because they have lots
and lots of different things that would work. Anything that you buy needs to be either aluminum
or stainless steel… No plastic because you’ll melt through it. Anything you can find that’s tall enough to
fit your knife in is perfect. Then you’re going to need a torch. I use a
Bernzomatic TS4000, this is a relatively expensive torch, it costs about $40. It works very well,
and it works with both MAPP gas and propane. So if you need a hotter flame for brazing
or whatever then this is a great torch. If you are looking for cheaper torches there
is one thing that you need to be aware of and that is: if you look at this torch you
can see that the inlet holes for the burn tube are right down here which means that
they’re almost 6 inches away from the head of the flame. On this cheaper torch the air inlet holes
are only about an inch away from the head of the flame, what happens is that the burnt
gases will recirculate into the air inlet hole when the torch is used with a forge because
something else is in such close proximity with it. If you’re looking to buy a less expensive
torch is to make sure that the air inlet holes are as far away from the head of the torch
as possible. If it too close, like this one, then it will work fine as a blowtorch but
it won’t work with a forge or for heat-treating. The next thing you need is a forge. This one
is a very simple home-made one it’s basically just made of 2 fire-bricks that have semi-circular
channels cut into them. And an inlet hole at the front. The flame goes in at an angle,
angled toward the rear, then swirls around the burn chamber before it exits at the back. Having the flame right at the front lets you
move the blade in and out while you’re heat-treating it to get an even heat from the handle of
the blade all the way to the tip. If you have the flame entering at the back
then you’ll be able to get the tip very hot, but you’ll have a hard time getting the rear
of the blade, the tang and the ricasso hot. So I recommend having the hole at the front,
it works really well. The next thing you’re going to need are fire-proof
gloves. I use welding gloves, and these work pretty well. They’re not the most comfortable
but you need something that’s quite flame retardent because if your quenching oil catches
on fire or spits up a big burst of flame when you first put the hot blade in it can burn
your hands quite badly if you don’t have gloves on, so I recommend wearing gloves. And then finally, unless you like burning
your house down, I highly recommend that you have a fire extinguisher on hand. Using water
to extinguish an oil fire is extremely dangerous and you shouldn’t do it so make sure you have
a dry powder fire extinguisher at hand that’s suitable for use on oil fires. Here you can see how the propane torch is
setup in relation to the forge. The flame is angled upward, and toward the rear of the
forge. This helps ensure that the heat is distributed as evenly as possible by causing
the flame to form a spiral around the inside of the forge. After letting the forge heat up for several
minutes, the next step is to pre-heat our quench oil. Warm quench oil will actually
cool the steel faster, because it forms less vapour bubbles around the blade during the
quench. To pre-heat the quench oil I am simply heating
up a piece of scrap steel and then plunging it into the quench container. Now it’s time to start heating our knife blade.
Notice that I’m constantly moving the blade around in the forge. This helps ensure that
I don’t over-heat any particular part of the blade. What we’re looking for is an even dull
cherry-red colour. If parts of the blade get hotter than dull cherry then they may end
up being brittle. You can see that the thin parts of the blade
heat up the fastest. Keep them away from the direct flame and make sure to continuously
move the blade in order to get the heat as even as possible. It will take a few minutes. After the blade is an even, dull, cherry red
colour, remove it quickly from the forge and plunge it straight down into the quench oil.
You only have a few seconds to get it out of the forge and into the oil. Be careful
of where your hands are, as the oil will often catch fire on the surface for a few seconds.
After the blade is in the oil, make gentle slicing motions with it to help cool the blade.
Do not move the blade sideways as this may cause warping. After the blade has completely cooled from
the quench, we need to test that it has hardened properly. To do this we run a file over the
edge and spine of the knife. If the knife has hardened properly then the file will simply
skate over the surface of the steel. At this point the knife will be extremely
hard, but also quite brittle. If you were to drop it accidentally it would probably
shatter. So the last thing we need to do is to temper the knife. This process gives up
some hardness in the steel in exchange for much more toughness. To temper the knife we
simply heat it to an elevated temperature and keep it there for a while. In this case
we’ll be heating it to approximately 400 degrees farenheit and keeping it there for 2 hours.
I’m using a toaster oven for this process, but you could also easily use a regular household
oven. After the tempering process is complete, your
knife blade will be hard and hold a great edge, but it will also be tough and resilient.
At this point the blade is ready for final finishing and use.

100 thoughts on “How to heat-treat an O1 knife blade using cheap common tools.

  1. What happens if you forget the knife in the toaster oven for 8 hours?? I accidentally did that and am wondering if I trashed 3 blades? Seems like the edges are brittle but don't not know if that's because I over heated them as well, sorry if this makes no sense

  2. Would this method be more for 1080, 1084 or 1095 steel as I think 01 tool steel needs to be heated at 1500F for 10 to 30 minutes before quenching to get best results?

  3. Would this work for Damascus Billet 1095 and 15n20? I know for the 1095, 1084 and 1075 stuff.. what other steels will work with this forge and do I need to check for magnetic prior to quenching.. ? brick type you use in this video? Very good video BTW. thanks

  4. Good video and clear instructions. Just wondering if you simply air cool after tempering or do you quench to stop the tempering process?

  5. hey do you need to normalise the steel before heat treatment? if so how many times? I'm a bit confused on this point

  6. I'm buying a propane torch and fire brick tomorrow. I've got everything else..

    Super nervous about the blade cracking. I worked really hard with hand tools to make this knife and I don't want my effort to be wasted. My blade is a bit over 1 inch long, so it shouldn't take very long to get it to cherry red. Wish me luck, I guess.

  7. +Gough Custom
    Aaron I know this is an old video, but I think I fudged the heat treatment. The blade was dull cherry red in the forge, but not red when pulled out and the oil didn't flare, also a file left marks. I was concerned about over soaking it past cherry, but when you say that do you mean it should be dull cherry red outside of the forge…I mean glowing 'red' going in the oil?

  8. Hey everyone, I'm building one of these firebrick forges, but I have a question. Here in the Netherlands, butane torches are very cheap and easy to get, but propane torches are rare and very expensive (80 euro+). I was wondering if a standard butane torch would get hot enough in these kinds of forges to heat treat 01 tool steel? Thanks!!

  9. I know this has snowball's chance in hell of getting answered … But how thick should I leave the edge in order to prevent warping?

  10. I agree with everybody else commenting in here; this is by far the best and clearest how-to. easily doable at home for anybody to do. One question tho, in order to make a good sturdy knife that can survive almost anything you throw at it, do you only need to heat treat (the factory steel) ONCE? and what about the handle? Doesn't it need to be cherry red hot in order to toughen it so it won't break easily? I hope you (or anybody with the knowledge) responds!

  11. Do you find it beneficial to normalize the blades (heat to non-magnetic, allow to air cool) before heat treating?

  12. I agree with other commenters that this is the clearest instruction by far. Do you ever use a magnet to test for hardness, or is monitoring the color a better method? Thanks for the excellent instruction!

  13. Hey! Great video! Question… I want to heat treat stainless steel.. will this process work for this? If not do you have any recommendations for me on how to do it/learn?
    Also will it change the "stainless" properties of the steel significantly by hardening it?

  14. Any thoughts on using an induction forge? I'm getting an induction machine for heating firearm brass similar to the one here: https://www.youtube.com/watch?v=57RL5v54FhM

    Would that work?

  15. Very clear and well presented video.
    The only thing I would add is a magnet to test for critical temperature.
    When the steel is hot enough for quenching, a magnet will no longer stick to it.

    This is a lot easier than trying to judge the temperature by color, especially for a beginner, or if you are unable to work in a darkened area.

  16. Hi! Thanks for the great videos!
    I built a very similar forge and experimented with it.
    It works well but I can’t harden the steel properly… I need some tips please 🙂
    I used the magnet trick to find the right temperature.
    Four times the magnet was not attracted anymore, the four times I heated up steel again after the magnet test, then quickly cooled it with oil (vegetal).
    All pieces of steel failed the file test. I could still grind the steel by forcing a bit.
    And I tried to break the steel to test if I became brutal, but instead it just bent without being tempered…
    What am I doing wrong?
    Is it possible that the steel I used requires a different hardening method?
    Or could it be my magnet that is not strong enough?
    The steel was close to orange when I cooled it down…
    I’m in Germany, the shop calls it “Gezogen Stahl” (drawn steel).
    https://products.alfer.com/en/Products/Hardware/Steel-profiles/Standard-profiles-Steel-drawn/Flat-bar-drawn-steel.html
    They don’t give the composition of that steel.
    Should I use a specific steel?
    Thanks again for sharing all these vids.
    Cheers

  17. I been wondering if I can use my lil torch to heat treat a blade, now I know I can.. how long does the tank last ?

  18. Hi… how are you. I have a question you might know. I been playing around with heat treating a blade in the FORGE and Quenching it in oil . Using a skill saw blade and ONLY HEAT TREATING THE BLADE.

    NOT BAKING IT IN THE OVEN AND BRINGING IT BACK. I then tested the knife by throwing it at a tree and chopping with it.
    The blade Did not break and keeped a good edge. I am wondering if this Method is used or is it a bad thing. Blade is fine. No chips, no breaks and still have Flexibility because I did not heat treat anywhere else besides the blade . Did I Discover something new or is this done by knife makers ? Can use your Opinion

  19. Saw it here https://en.m.wikipedia.org/wiki/List_of_blade_materials It is under the tool steel paragraph, under A2 tool steel

    Real neat

  20. Is that a bologna can that's holding the fire bricks? Lol… what ever it is I like the set up and would like to find one like it. Thanks for the great video

  21. Hello new subscriber. I have access to high quality table saw blades, would I need to heat treat the blade or would it be hard enough already?

  22. Hey – I'm trying to heat treat my knife and am somehow screwing up, it's not getting any noticeably harder. I'm using 5/16th inch O1, heating it up until it's no longer magnetic (then a bit hotter), then plunging it into a mix of sunflower/motor oil. Any thoughts on what I'm doing wrong? I've done a bit more reading and some say that the knife needs to be at the red hot temperature for about 10-20 minutes. Other than that, the only other thing I can think of is I'm not using the right kind of oil?

    Cheers from the west coast. Great videos!

    PS It's fantastic seeing that you reply, quickly, to anyone that has a question. Can really tell that you're passionate about this stuff, and helping people learn

  23. Hey Aaron, just heard O1 steel needs to held at around 1375 degrees for approximately 10 minutes to get the most of the steel. Do you recommend, getting the knife blank up to around 1400 and slow down on entry of the blade to try and maintain that temperature the best you can. Do that for 10 minutes, then get it all the way you 1500 (nonmagnetic)? Or is worth it.

  24. hey aaron first of all i would like to thank you for your instructional videos and second ive found that i need to get 01 to a redish orange color to get it hard ive tried dull red but the file test will easily leave marks. (under dim light)

  25. I'm from the Ottawa area. Can you recommend a good source for steel in Canada that I can order online? Currently using Canadian Knifemaker out west but they have limited variety. Also, built the forge and treated my first knife last weekend – thank you very much for this video!

  26. First of all, thank you for all the vids you are making on the topic! They are really clear and remove almost all questions one would have about different stages of the knifemaking process. Definitely the best material on youtube.

    My question however would be what exactly is the material used for the bricks in the forge? Is there any way to simplify the structure, perhaps so one could make it at hime with a chisel and a hammer?

    Thank you and keep up the great work!

  27. First, they are called waterpump pliers not vice grips. Second you didn't have both gloves on and the hand closest to the oil was exposed. Other than that great video dude!

  28. Firstly, tremendous video. Crystal clear. I built one and hardened my first knife successfully. File is now skating along without marks. About to temper. I had a funny thing happen though. I let the torch go for about 10 minutes to pre-heat the forge. Then did the knife. Took about 3-4 minutes to become non-magnetic. After quenching in peanut oil, I noticed that the whole trigger area the torch (which is identical to yours) was completely covered in ice!!! Have you ever seen this? Please keep up your amazing channel. Regards, D

  29. Very clear instructions but I would add one step. Sand the blade clean after quenching before annealing. The clean surface shows the surface color of the tempered steel – should be a straw yellow. On the black surface you won't see them. I think this is important.

  30. I read somewhere that 01 needs to soak for 20 to 30 minutes at final temperature. Does that just make it harder?

  31. Hi Aaron, thanks for all the help with these videos and responding to my comments. So I’ve tried to replicate this process with O1 tool steel and essentially a set up identical to yours and the best I’ve been able to acheice after tempering is 52 Rockwell hardness (c scale). I’ve been told that’s too soft and I should be getting nearer to 60 hrc. What am I doing wrong? I tempered at 450-500 for an hour after heat treating and quenching in the manner you show. Thanks for any help.

  32. This a very thorough video. Thanks for posting it. How did you drill the lenghwise hole in the firebrick?

  33. Might sound like a daft question buy if you got one of those cheap torches and drilled a few wholes lower down would that work better?

  34. Easiest heat treatment for O-1 I’ve seen. I’ve been holding on to a 3’ flatbar but now with this knowledge I’m gonna go for it! Have you ever tried O-1 on a long blade like a short sword.

  35. Best. Videos. Ever. What other steels can you heat treat like this? Can you do your 154CM’s and s30V’s etc like this? Have always been curious. I’m guessing no but thought I’d ask. Cheers.

  36. Finally. A low cost yet effective method to do this without sending each knife out for treatment or spending $$$ on a forge. THANK YOU. For this video, did you use MAP gas? What is the diameter of the hole at the back of forge? Same as the front?

  37. Great video! Excellent flow and excellent explanations. Thank you very much, I subscribed and saved to watch again.

  38. very good video, the 01 must be at 800-820 degrees for 15-20 minutes, you measured hardness, I want to see what we lose if we warm it in a detail like you, sorry for my english, good from greece

  39. Hey Gough,

    What is your recommendation on having a hole in the back of the forge? Did you just do this for ease, or is for a practical reason? I see people covering it up or not drilling/cutting all the way through.

    Thanks!

  40. Thanks for explaining the safety precautions and the clear reasoning for each tool used. I'm excited to give this a try!

  41. its not just dangerous to try to extinguish a fire with water, it freaking explodes, so please be careful my guys

  42. 5 years later and your videos are still passing on wisdom! Thanks a ton for the effort and information, I'm watching this just before I attempt my very first heat treat on some scrap.

  43. YouTube is amazing place full of awesome people like yourself. People who helps others like me.
    Subscribed and liked your channel. Thank you for your work and videos!!!

  44. Have you noticed a difference between heat vs quench and heat soak and quench? Just wondering if you find one is better than the other?

  45. I like how you devised a statistically sound random test. This is a very informative and systematic approach.

  46. Dude. What a great video. I have been wanting to learn how to temper O1 steel for 4 years. I make dies for swaging and reloading ammunition. Have used Grade 8 bolts because I thought heat treating was too complicated. Now I can use the proper steel and make far better quality tools. THANK YOU

  47. BTW, most knowledgeable smiths say that 01 must be heated to 1450-1500 and held for 20 minutes before quenching to get the most out of the blade. Do you agree? Why/why not?

  48. This doesn't go directly to the tools involved in heat treating, but it does go to tools. What kind of mask filters should I use if working with epoxy and grinding metal?

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