Transcription
Today, we are going to be looking at whether you can realistically heat treat a knife with this. And these, it's probably the cheapest way to heat treat, and I'm going to be giving it a test. The heat training forge I'm making uses a propane plumbing torch and two insulated soft fire brick. I'm looking at the prices right now, and you can get all this stuff for about 80 bucks. I'll leave links to what I can in the description if you're interested. And as of now, this is probably the absolute cheapest way that you can heat treat a knife.
Now, the information and techniques used in this video are only going to apply to one specific steel. That steel is 1084. 1084 is a very beginner-friendly steel to work with, as you will see in this video. But don't apply this information to other steels unless you do specific testing for those particular Steels. Heat treating is very, very steel-specific. So buying the appropriate steel for your heat treating method is absolutely paramount in getting a good heat treatment. If you try to heat a piece of M4 in a mini forge like this, you, you're going to have big problems.
1084 is a very good steel. I still use it to this day, even though I have all of the fancy knife heat treating equipment. It has fantastic edge retention. If it's left hard enough, it is extremely durable. It is tough, and it's a, you really can't go wrong with 1084. It's also, again, extremely easy to work with, and that's what makes for a good knife is a properly heat-treated knife with the proper steel. So again, make sure that you're buying the appropriate steel to heat treat in a forge.
Making one of these is extremely simple. You'll need some sort of large drill bit. I chose to use and ruin a Forstner bit. You can also use a spade bit if that's what you have on hand. You want to make the hole as small as possible so that it's less volume to heat and the forge will get hotter. I used a one and one-quarter inch bit that just fit the size of my knife. You will have to rig something up in order to drill the length of the brick.
Now, a lot of people have asked if this can be done using a single brick, and that's what I'm trying here. But once I got the finished product and tested it, I ran into some problems. It cracked as soon as I started to heat up the forge. So no, I wouldn't recommend making one of these out of a single brick. You're going to run into problems.
So, start it over. A better option is the double brick method. So I stack the two bricks together, took my long Forstner bit extension thingy, but again, a long spade bit would work better, and drilled out a one and a quarter inch hole down the middle of the two bricks. If you don't have a drill bit long enough, these bricks are very soft, and the channel can actually be scraped out by hand.
Next, I'll put the bricks on top of each other and drill a 5/8 inch hole for the torch to go through. Now, I'm drilling this hole off-center so that it enters the burn chamber towards the bottom, so that the flame will hopefully create a swirling pattern inside the burn chamber. And then here, I'm just taking an old junk knife that is ruined and cleaning up the transition from the torch into the burn chamber. And that's pretty much it. Insert the torch and turn it on. Make sure that the torch is fully inserted, otherwise you may get some flame coming out of the hole where the torch fits, and that's probably not good. I don't have any scientific evidence to back that statement up, but it's probably not good for the torch.
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And we'll give this a quick test with a junk knife. So it's been a while since I heat treated in a mini forge like this. I mean, it's been years and years and years at this point, and I couldn't remember exactly how long it took to bring the knife up to heat treating temperature and whether or not it really was a viable option for heat treating. To tell you the truth, I'm actually really surprised at how quickly this thing brought that knife up to heat treating temperature. I mean, it was maybe a minute. It was really, really fast. And I think a lot of that has to do with the size of that burn shaper, making it as small as humanly possible, as small as your knife will allow. The smaller that burn chamber is, the better, because obviously you're not heating up more space. A bigger burn chamber than what your torch is able to heat up. So keeping your burn chamber small is definitely going to be key for making one of these things work. These are not going to be for heat treating like giant machetes and stuff. These are for smaller bushcraft, smaller like EDC type knives.
So I'm going to do now is lengthen the burn chamber just a hair so that I can get the blade in a little bit farther to allow more even heating in the entire blade length. And then I'm going to go ahead and grind out a couple of test planks. I'm going to heat treat them, and this forge, I'm going to quench them in Parks 50, which is going to be key. I'll talk about that here in a minute. And then, um, we'll put them on the hardness tester to see whether or not I can get a decent hardness out of them using a really cheap, really crude heat treating method. So what I'm doing now is lengthening the burn chamber so that I can get the entire cutting edge in contact with the flame entering the burn chamber. You want to be able to get the entire knife edge into contact with the flame. So size your burn chamber and spacing of the torch opening within the burn chamber to allow the flame to come into contact everywhere on the knife edge. This will allow you to better control where you heat and how much you heat along the edge.
So rather than doing little test coupons, I decided to do an entire knife test blank, and I'm glad I did. And you'll see why in just a second. You're going to want to heat up the forge for a number of minutes before you start the process. Make sure the forge is good and hot before you insert the blade. It will help with even heating, which again, you'll see why this is super important in a minute. Also, use a proper quenching oil for the steel you are using. I'm using Parks 50 for this 1084 steel, and this is an absolute must-have in my opinion. Don't use canola oil, motor oil, olive oil, transmission fluid, or any other type of oil, or you won't get full hardness. Trust me, you're better off just using water than the incorrect oil. Water is a super fast quench, so you may run into cracking issues, but at least the blade will be hard. There is a lot more to this topic than we are covering here, but we'll just leave it at that.
Starting the heat treating process now. I'll insert the blade, trying to make sure I heat everything as evenly as possible. You really want to focus on heating the cutting edge as evenly as possible. I'm using a magnet to indicate when I have the blade hot enough, since when the steel becomes non-magnetic, that indicates we have surpassed the austenitizing temperature of this particular steel, and we can go ahead and quench the blade. This is a very basic principle and description of this particular heat treating process, but we are also using a very crude method of heat treating, so it sort of fits. So you can see me here testing it with a magnet, and it's still magnetic. So back in the heat it goes, and I test again, and boom, non-magnetic.
Now, this is where I made my mistake. I only tested a single area of the blade, the middle. I should have tested the entire cutting edge. Now, in real life, I'm not able to see the colors as well as you can see them here on the screen. Looking into a forge is kind of like looking into a dim sun. It's kind of hard to distinguish different colors when you have an overbearing bright spot. So for me, the entire blade looked uniform in color, thus I assumed I had heated everything evenly. This was not the case. Hopefully, we got this thing hot enough, especially down here, I'm kind of concerned about, and maybe even up here towards the tip of the blade, I'm not sure. So let's clean it up, and we'll put it on the hardness tester. Quick grind to clean everything up, and onto the hardness tester to run a million hardness tests.
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And Houston, we have a problem.
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The results are in. I tested all up and down the blade a bunch of times, reground it, tested it again on both sides, and I have consistent results all the way around. So it looks like between the middle, between the tip of the blade and heel of the blade, we're good. 65 and a half. We can run with 65 and a half all day long, temper this down to 60, 61, and be, and be great. We'll have a decent heat treatment. Problem is, is that I think the problem was, was actually me. I failed to get the tip hot enough, and we're testing in the low to mid 40s up here towards the tip, and the low to mid 40s down here towards the heel of the blade. And I, I think I just screwed up. And I think that sort of highlights, uh, uh, one of the big problems with heat treating in a forge is that a lot of it is up to the operator. How good of a job did the operator do? Now, if your operator is doing testing afterwards to sort of do that quality control, then that's great. We know that we'd have a bad heat treatment on this knife. If your operator is not testing after quenching and a forged setup like this, you really have no idea whether or not you got the blade hot enough.
So let's try this again. Now, I had a hunch that I didn't get those portions of the blade hot enough right out of the quench. And if you remember, hopefully, we got this thing hot enough, and it looks like I was correct. So we're going to try it again with another knife.
Thank you. Same setup as before. I let the forge pre-heat for about 10 minutes this time. Then I said, screw the filming, and turned off all the lights in my shot. I did this so I could more easily see the color uniformity within the steel. I'm not paying attention to the exact color of the steel, only the uniformity. So as I use the magnet to test, I simply try to match the color from the non-magnetic portions uniformly throughout the entire cutting edge. And once I had the entire cutting edge completely non-magnetic, I quenched and set off my smoke detector. It's nice to know that they're working. I'll wipe off the blade, take it over the grinder to grind the flats flat, and then over to the hardness tester to run another million hardness tests.
66 and a half. That is fantastic news. 65 and a half. No, I'm sorry, 66 and a half to 67 along the entire cutting edge, all the way from heel to the very tip. So we had really good even heating. This forge was definitely able to get us up to the temperature we needed, and, uh, we got the hardness we were after, almost 67. The only thing that, uh, the only question that remains at this point is, what does the grain look like? If we do a snap test, are we going to get really coarse grain? Did we way overheat it for way too long? Are we going to have fairly, uh, fine looking grain when we do the snap test? So the only thing left to do at this point, since we have, for all intensive purposes, a decently heat-treated blade in a mini forge like this, we'll go ahead and snap it and see what it looks like.
So if you saw my, uh, previous video from several months ago about how dangerous hardened steel is when it breaks, take all the safety precautions that you possibly can. This stuff is actually really dangerous, and it will mess you up if you start, uh, if you get a piece of this coming at you at like 250 miles an hour, it will, uh, definitely do some damage. So be careful doing this.
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All right, so here's what the snap test looks like up close. Looks like we have a fairly refined grain pattern within the steel. We had a nice clean, quick, easy break when we, uh, snapped it. That's exactly what we're looking for. So it seems like we got a really good heat treatment off of this relatively crude setup.
So this is very hard to tell in person, but once viewing this on a bigger screen up close, the grain could definitely be a touch finer. However, I think it's still very good considering our setup and lack of temperature control. Two soft fire brick, a propane torch from Home Depot or Amazon or wherever you want to buy this thing, wherever is cheapest, and Parks 50. Cheap magnet, and you can heat treat a knife with excellent results. Don't let the heat treating side of things hinder you from getting started in knife making. Buy a couple of bars of steel and experiment. Mess up a couple of knives. Practice heat treating. It's kind of fun. I haven't been this excited. It's funny, I have all the fancy equipment, and this was actually really fun to do. Make a mini forge like this and heat treat as cheap as possible. So don't let it intimidate you. Go out and just get it done.
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