The knife is one of the most indispensable items for a human in the woods. While a great deal of materials can be fashioned into a functional blade, including stone, steel, bone, or even wood, here’s how to make a knife for survival from ‘scrap’ or found steel – from damn near anything. Oh, and it’ll be wicked-sharp. You can even carry this one in your wallet. Meaning it will always be on you when you need it. You know, like in a ‘survival situation’.
The inspiration for this article came from an Apprentice of mine who asked a question akin to: “Could I make a real knife out of whatever I can find in the woods?” He was dismissing stone flake knives and even bone knives. He wanted a legit, steel knife. That could, you know, cut stuff – like any other knife.
It, first, begs the discussion of what makes a ‘knife’. I don’t know about you, but I can’t cut stuff with my bare hand. Maybe my teeth or somebody else’s fingernails, but the flesh of my hand? Nah. Even if I have the world’s worst steel knife, it’s at least 99% better than trying to cut stuff with my own hand. (Check out our related article on what makes a ‘survival knife’.) And 90% or more of the stuff we do with a knife is cut things: cord/rope, kindling, tinder shavings, hide, etc. And with that simple knife you can make pounding and splitting tools (wedges, etc.) from what else you find. Sure, it’s great to have a fancy high-end knife that does the work for you, but how many people have the ‘perfect’ knife at their hip when the SHTF?
A knife of any sort, especially one that’s sharp, is far better than none at all.
The question from my Apprentice, as well as inspiration from engineer and primitive technologist Dick Baugh, bore this article.
You can absolutely make a knife from what you find laying around. This article will explore the fundamental necessities of making a knife from found steel. You can scale up these basic techniques to virtually any type of knife. If you want to take a 5-part video course on making the knife below, try out a free 2-week trial of our distance-based study program, THE PACK.
This begs some questions, and terminology, around knife-making. Here’s what’s important for the sake of this article:
- Steel – is an alloy of iron and carbon. Iron makes up the majority of the composition and gives the knife its body as well as softness and ability to be sharpened. Carbon (only a fraction of the steel, up to about 2 or 3 %) allows the steel to be hardened and tempered. Steel is considered (rather unarguably) one of the greatest innovations of humankind.
- Fatigue – when steel weakens, due to stress, to the point of failure. Most often (for the sake of this article) due to repeated bending stress.
- Anneal – is to soften a piece of steel. When we heat, and slowly cool, a blade it allows the molecular structure of the steel time to slowly orient itself into a position that makes the steel softer.
- Harden – is when we heat, and rapidly cool, a piece of steel. It traps the molecules in a position that makes them hard…and therefore, more brittle. Note: ‘Hard’ does not mean ‘tough’. In fact, the opposite is true. When something is truly hard, like glass or obsidian, it is also fragile and susceptible to breaking due to impact. Conversely, relative ‘softness’ mean’s toughness. A softer steel can withstand impact better than a harder one. (Compare the hardness of a hammer to a knife. Or a nail to a screw. For you folks in the cheap seats, think of Play-doh versus glass. Soft v. Hard.)
- Temper – the temper of a piece of steel is its relative hardness (typically measured according to the Mohs scale). To ‘temper’ a blade is to draw back (soften) its hardness into a state that’s more appropriate for its future use. (Too hard and it can shatter, too soft and it will maleate itself into another shape upon use.) From soft to hard, common steel tools would include the hammer, then the axe, and farther along, the knife. Softer tools withstand impact better (hammer). Harder tools are able to be more finely sharpened (knife) or, rather, hold that edge.
To make a functional steel knife, you could use almost any scrap of steel (iron + carbon), including a piece of soup can (no longer ‘aluminum’ or ‘tin’). You could grab almost any piece of metal that appears to rust. For simplicity’s sake (and limiting variables for this article), we’re going to use a length of (high carbon steel) hacksaw blade. It’s about a half-inch wide and less than 1/64” thick. Got teeth on one edge.
Do I expect you to find a pristine hacksaw blade laying in the woods? Of course not. If that’s a real question, you need to go back to our kindergarten level of knives. I’m simply modeling best practices for creating a wicked-f’ing-sharp knife (all you need) from a piece of ideal steel. Soak up the practices and physics, then experiment.
First off, grab a thin piece of steel. The thinner the better, as a blade’s sharpness is directly related to the thickness of the original stock, whether it’s to be a knife, axe, etc. While I don’t love to support the company, the High Carbon Steel (HCS) blades sold by Harbor Freight are a good starting point. HCS is better for this project than High Speed Steel (HSS), which is typical in many hacksaw blades (as well as drill bits, etc.).
You could find a soup can, flatten it with your heel, and bend those hinge points back and forth to the point of fatigue. Sharpen that edge a bit and you’ve got a crude knife.
Want to create a better one? Read on.
For the sake of this article, I’m going to assume you have a HCS hacksaw blade. But this same process will work for an old file (which tend to have good steel, check your local flea market) or even high-end tool steel. Start small (and cheaply) and scale up. Within this article, you’ll also read references to other steel sources and see pictures of ‘file knives’, etc.
Step 1 – Anneal
- We anneal (soften) a piece of metal so that we can more easily shape it.
- Heat your hacksaw blade to the point of glowing (cherry red to orange is good – more on heat temperature by color later). On our courses, we often heat our steel in a wood-fueled rocket stove (although the temperature is limited if you’re using wood fuel). You can also use a really hot campfire. Place the steel in the hottest part of your ‘furnace’. Know that the thickness, ambient temperature, position, wind, etc. can affect the even-heating of the steel and/or cause it to warp later on. With a hacksaw-blade-made-knife (being so thin), it’s best to plan for warp-age. Toss several blades into the fire/rocket stove — and plan to make a shorter blade.
- Heat the blade to glowing, continuing to stoke the fire if necessary. If you can’t see the blade, just burn a really hot fire for several hours (a hacksaw blade can heat to glowing in under an hour if the fire’s hot).
- Cover (or otherwise insulate) your fire so that it will slow its cooling as much as possible. Ideally, leave the fire/coals (and steel) to cool down overnight. (But always maintain your fire safety protocols.)
- Come morning/cooling (to the touch), your steel will be ridiculously-softer than it was prior. You’ve just annealed steel.
Step 2 – Create a Blank
You could grind the entire thing down, but it saves a lot of time (and energy, which = calories on survival) to create a ‘blank’ as close to your desired knife as possible.
- Sketch (or at least picture in your mind) what you want the final blade to look like. (On a hacksaw knife, I favor a slight drop point to place the point of the knife closer inline with the centerline of the width of the blade. Otherwise, I usually go for a straight back and gentle curve to the blade.)
- Grab the hacksaw blade just outside your sketched line (I usually aim for about a 45-degree angle) with a pair of pliers or wooden tongs, if you have them. Bend the excess material back and forth until the metal fatigues and it breaks. This should only take a few times. (Alternatively, without additional tools like pliers, you can do this with your bare hands if the steel is properly annealed. It will be less precise so you may want to err on the side of caution and leave additional material in place.)
- If you need to break off the other end, repeat the process above.
- **Note: If you’re using heavier stock, like an old file, it can be easier to create a blank by breaking it (rather than bending), even before annealing. It’s more crude, but since files are so hard (brittle) they’ll break easily. Simply lay the file across a gap (ex: between the ground and a rock) and smack it with a hammer, rock, or even your heel. (Wear safety glasses, or at least close your eyes if you find a file…in a real survival situation.) It will break unpredictably, so be prepared to make a knife dictated by the breakage.
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Step 3 – Grind the Profile
This is where your scrap metal starts to look like a knife. To limit variables, you’re only going to worry about the side profile. That’s the shape that the overall knife will look like. (Like when you look at the picture of a knife in a catalog or online.)
- If you haven’t already, it’s really helpful to draw exactly what you want your knife to look like on the face of the steel. A pencil is great. A tiny piece of charcoal will work.
- File or grind away the extra material until you reduce the stock to the pencil line:
- I like to clamp the hacksaw blade onto a sturdy bench or in a vise, then use a hand file to carefully shape the blade profile. Be cautious to file roughly parallel to the length of the hacksaw blade. (Filing perpendicular can bend the annealed steel.)
- Don’t have a file and clamps? No worries. Grab a coarse stone (sandstone is ideal; many granites will also work) – something akin to sandpaper – and go at it. Adding a bit of water (making it a wetstone/water stone) may aid in creating abrasion due to the ‘slurry’ it creates to fill the gaps in the stone. You’ll be surprised at how fast this can go.
- If you want to remove the teeth from the hacksaw blade (or do any additional shaping to other parts of the back, blade, or handle, this is the time to do it.) Again, don’t worry about sharpening the actual knife edge.
- Shaping hacksaw blades this way can take just a few minutes. Heavier stock (like a file) will take much longer.
- “Can I use a bench grinder?” Typically, you’ll want to avoid using a standard bench grinder to shape or sharpen steel tools, because the speed/friction is so high that the grinder will heat your steel beyond its temper. That means that you can inadvertently soften your steel. (An example would be sharpening an axe on a grinder — typically a no-go.) But if you’ve appropriately annealed (softened) a piece of steel, want to do this in a hurry, and plan to harden/anneal in the future, then there shouldn’t be much problem with resorting to your bench grinder. (Especially if you have one in a survival situation.)
Step 4 – Create the Edge
You should have a blank — something like looks like a knife from the side, but is dull.
- My favorite ‘grind’ for a crudely-made knife like this is the same as my favored grind on any other (store bought) knife: the Scandinavian Grind. It’s a simple, one bevel (two-faced) edge that angles directly from the widest point of the stock to the cutting edge. It’s a single angle. It’s the easiest grind to resharpen (and make). (Compare the Scandi Grind to a Hollow Ground knife, which would be far more difficult to make in a bush setting.)
- Look at the blank from the end. You should be looking at a cross-section of the blade. Visualize a tall, skinny isosceles triangle, with the apex of the triangle at the knife edge and the two identical ‘base’ points at the widest point of the knife stock. That is the angle you want to grind into each face of the blade. For thin stock, that will be ridiculously steep. And that’s good. Steepness = Sharpness. Try to really digest that angle you’re dealing with.
- Ideally (using a file and clamps), clamp the blank flat to a surface. If you’re grinding the blade against a stationary piece of stone (that granite boulder you’re sleeping near), the process is fairly similar – you’re just moving the knife blank instead of the grinding tool.
- Lay your file roughly perpendicular to the knife blank (angle the file slightly toward the knife tip). Before beginning to file, adjust the angle of the file (from the horizontal) to match the angle that you visualized (above) for the future knife edge. Maintain that angle throughout this entire process.
- Begin filing. Remember that files are designed to cut on the PUSH (teeth are angled away from the handle end), so push hard and forward, then lift and return to your starting position. There is little to be gained from trying to file ‘on the pull’ and this can actually dull the file’s teeth in the long run. The file should move forward along the length of the knife blade as you push. If you’re making a short (2-3″) hacksaw blade knife, you should be able to file the entire length of the blade with each push.
- Maintain your perfect knife-edge angle as you file. There may be a tendency to want to start out at a steeper ‘up’ angle and then flatten later in the process. I suggest avoiding that urge, as it can lead to a curved edge bevel instead of a flat one. It will be a duller knife and the wider ‘cheeks’ from the curvature make for friction against material even after the edge has done it’s job. (This is the opposite of the edge you want on a splitting axe, where those wider cheeks will give you exploding power to wedge wood apart. Here, you want the sharp edge to do the work and the bevel to get out of the way — hence the original reason for the Hollow Grind.)
- Unclamp and view the knife from the end regularly. You don’t want the edge to go past the centerline of the stock. If you’re dealing with thin material (hacksaw) this will be difficult to see and very slight. With wider material, you may even be able to draw a centerline down the flat edge for reference.
- As you approach the centerline, flip the stock over and repeat the process from the other direction. You may need to flip back and forth a few times to even-out the bevels on both sides, making them symmetrical.
- Aim for ‘sharp’, but not SHARP. Making your knife edge too thin/sharp at this point risks cracks during the hardening process. We’ll do a final sharpening later.
Step 5 – Harden
You should have a ‘sharpened’ but soft knife at this point. It will cut most stuff just fine (actually, probably better than 95% of the EDC knives carried by most folks who don’t use or sharpen their knives). In a pinch, you can use this ‘knife’ as-is. But read on for how to make it perfect.
- Once again, heat the knife to glowing (orange to cherry-red).
- You can do this as crudely as throwing it back into your super-hot campfire.
- A better crude-campfire hardening can be had by isolating a flame source: Arrange heat-tested stones/bricks over the flames with a narrow crack between them, so that a ‘tongue’ of fire shoots upward between them (very primitive blast furnace/rocket stove).
- If you’re less concerned with the primitive, use a standard propane torch to heat the blade through. Begin by slowly passing back and forth over the blade. Heat both sides. Then get closer and light it up with the heat of the torch. (Best used in warmer environments and out of the wind – cold and wind will sap the heat from the metal (a conductor) very rapidly due to radiation and convection, making heating with a single torch very difficult.)
- Rapidly cool. In order to harden your steel, you’ll want to cool it as rapidly as possible. But too rapidly, and you may crack (shatter) your blade. See below for details on cooling agents. Regardless of the cooling agent, harden as follows: Grab hold of the glowing knife (in the fire) with a pair of tongs (steel or even wood, in a pinch). Rapidly transfer the knife from the fire directly into your cooling medium. Plunge it right in. Completely submersed. Gently slide the blade back and forth for 30 to 60 seconds (the blade is cooling). You’re seeking to shake off bubbles/air pockets and continually move to cooler medium (rather than the medium directly around the initially-plunged blade, which will be hotter). Note: Be sure to slide the blade parallel to its length; don’t swish it back and forth, sideways. Sideways stands a higher likelihood of warping the blade.
- Oil – My preference for cooling steel is in a room temperature, higher-flashpoint oil – like vegetable oil. Avoid flammable oils like petroleum-based ones. Liquid animal fat would be an acceptable replacement in a true survival situation.
- Water – Water is the classic quenching medium, but I’ve had some bad results. I’d made a beautiful hand-forged drawknife. It was perfect. I could even envision the bows I would carve with it. I quenched it in cool water and the edge cracked in 3 places. Ruined. In a moment. The heat transfer (cooling) can be so rapid in water that the steel can’t take it. Water is still a highly valuable resource for cooling a glowing blade, but be forewarned: Don’t practice on projects that you find valuable.
- Snow? – In a major pinch (survival), you might consider plunging your glowing steel into a snow bank. While you might consider the even-more-rapid-cooling effect to be the biggest problem, it’s usually not. The heat of the steel melts and evaporates the snow (sublimation) so rapidly that your blade will be surrounded by air (and not snow) in a moment. You could consider packing a tight snowball ahead of time, for cooling, but if it’s cold enough for that much snow, the ambient air temperature alone may be your best bet for cooling
- You’ve just hardened steel. It may not look like it, but that chunk of steel is now vastly harder (more brittle) than what you just had — or even, likely, than the piece of steel you started with.
Step 6 – Temper
Dial-in (draw-back) the hardness of your tool to exactly what you want. This is where the real art takes place.
- Tempering by Color Temperature
- While crude by modern engineering standards, a piece of steel can be tempered (adjusted to relative/appropriate hardness) according to the eye-catching color that it exhibits. Basically, the hotter the steel gets, the ‘brighter’ it becomes. The color the steel shows represents the temperature it currently holds. Think of it akin to the ROY-G-BIV color spectrum of visible light you learned in school. The color-temperature spectrum of steel is more like: Gray, Blue, Purple, Gold, Straw, White. With each color representing a hotter and higher temperature.
- If ‘stopped’ (cooled) precisely at each color-temperature stage, the steel will ‘freeze’ at that appropriate hardness/softness. For a knife, it’s great to have a purple color just hit the edge before cooling (setting in place).
- Heat your steel (knife)
- Ideally, use a propane torch or other direct and constant heat source to begin to reheat the blade. Heat from the thickest part, out. For most single-edged knives, that will be from the back of the blade. From the thickest point of the stock. If you’re using another heat source, the same rules apply. Using that ‘blast furnace’ brick setup over your wood fire (or propane stove) direct the heat to the thick part of the stock.
- Since the tip is thinner, it will heat faster. Avoid the tip. You want the entire edge of your knife to heat evenly.
- Watch for color
- It will happen quickly
- You’ve been heating up your blade for what seems like longer than it should take. But don’t get lazy! The color change happens rapidly and you need to be prepared.
- When the rainbow of colors begins to spread across your knife, be on high alert.
- At the moment the purple hits the edge of your knife, rapidly transition the blade into your cooling/quenching medium (oil, water, etc.). It should ‘freeze’ the relative hardness of the steel at that point. Perfect for a knife. Once you police the knife, you’ll likely even still see that rainbow trapped in time in your knife.
Step 7 – Final Sharpening
You now have a proper (but unsharpened) knife, more sharp and functional than the majority of commercial knives on the market. Here’s how to make it sharper.
- Basics – If you followed the filing instructions, above, then you’ve put a standard, single-bevel Scandinavian Grind into your knife. It’s one consistent face along the length of the blade. But if you look straight at the edge itself, you’ll see that it’s not sharp. In fact, it’s probably blunt. Maybe only 1/64″ wide, but that’s pretty dull when it comes to knives. Or axes.
- Quick tip: When you look straight at the edge of any sharp blade (knife, axe, or otherwise), it shouldn’t reflect any light. After extended use, it will likely have a few spots that you can see sparkle. (To amplify the spots, shine a light from over your shoulder.) You’re looking for reflections of any kind. A reflection is a flat spot. That’s bad. You want an edge so fine that there is no facet to reflect light.
- The Be-All-End-All-Secret-to-a-Sharp-Knife: Take care of it. Don’t abuse it. Once you have a sharp knife, don’t do anything stupid with it. Don’t carve dirty wood. Don’t use a stone or earth for a backing-block for carving. Don’t ‘sheath’ your knife in the dirt. Don’t let your blade touch anything that will dull it. That includes dirt, sand, glass, stone, metal, etc. It also means don’t scrape with your blade (a rule that I break). Don’t split with it (another rule I break). Your knife is a sacred instrument that can save your life. Take care of it and it will take care of you.
- Stones/Sharpening Tools
- Carborundum or other ‘coarse’ stone
- Diamond-plated sharpening stone (with coarse and fine sides)
- Homemade sandpaper/leather hone
- You’ll want to maintain the bevels you’ve already ground into your knife for this entire process. The angle at which you hold the knife should be the same that you filed into it.
- Two Methods: Circle and Straight/Drag
- Circle – My preferred method of sharpening a knife is the ‘circle’ method. It basically consists of isolating the blade to the predetermined angle and rotating in a circular motion over one section of the blade. As you continue, you’ll move up the blade a bit, continuing your circular motion. I favor this method because once you find the proper angle, it’s easy to maintain it (especially with the Scandi Grind). The main criticism is that it can leave circular/curved scratches on your blade (which isn’t a problem if you continue along the sharpening/honing process).
- Straight/Drag – The alternative main manual method is to ‘drag’ your knife blade along the stone, scraping the entire length of the blade in one motion. This looks sexier on camera but presents challenges related to maintaining the proper edge-bevel angle especially as you enter the curved knife tip area. It’s worth learning to use this method, but in my experience (personally and working with hundreds of others) it tends to lead to a duller blade than the one you started with. More often than not, when someone shows up to a class they’ve used a bunch and “resharpened”, I see a rounded face on the edge-bevel — and this is the method they’ve been using.
- First-time Sharpening: The process is basically the same through the first steps in this process. It changes toward the final honing.
- Moisten (water/oil) your work surface as necessary.
- Lay the knife flat on the sharpening surface (edge away from you). Tilt the knife up, toward the edge slightly until you feel it rest on the bevel you filed into it. (The edge-bevel should now be flat against the stone.) Begin the circular (or straight) motion described above. Work both sides of the blade, consistently.
- Carborundum/Coarse Stone
- The first time you sharpen your knife, you’ll put a fair amount of time in on your coarse stone. Much less later, if ever.
- Work one face of the bevel all the way down. Circular motion. With a hacksaw knife, this may only take a couple minutes per side.
- Keep an eye on the centerline of your edge. When you’re making the knife, it’s a flat (dull) edge maybe 1/64″ wide. If you sharpen too much on one face, you’ll shift that edge out of center. Switch to the other face as necessary, in order to maintain a centerline edge.
- Once you’ve gotten rid of any sort of ‘flat’ edge, move on.
- Diamond Stone
- Repeat the same process, both sides, as you did with the coarse stone. Work both sides evenly. Working-up a good slurry of spit and steel helps to polish and sharpen in the later, finer stages.
- After your initial sharpening, provided that you take care of your knife, you should only ever need to return to the coarse side of your diamond stone in the future. You should have no reason to retreat to a coarser (carborundum) stone, except to fix mistakes or blemishes – as is reshaping due to crunching a rock against your knife.
- Begin with the ‘coarse’ side of the diamond stone, then move to the ‘fine side’. Circular motions. Both sides.
- At this point, your knife is completely functional and sharper than 99+% of the knives being carried these days. It’ll likely even shave the hair on your arm. If you want to amaze your friends and terrify your enemies, continue on.
- Homemade Hone
- Change your technique – Until this point (if you’ve followed my advice), you’ve been using a circular method on a ‘wet’ stone. Dry your blade and pull out your homemade sandpaper/leather hone. You’re going to switch to the straight/drag method.
- Sandpaper – In one, slick swipe drag the knife bevel/edge along the length of the sandpaper. Repeat a total of 10 times. Then switch to the other bevel. Check for sharpness. Repeat, both sides. Check. Repeat as necessary. Then, move on to leather to make it Wicked.
- Leather – Ever notice how every Western ever made shows a barber sharpening a razor on a strip of leather? (It’s called a strop. Honing this way is called stropping.) The supremely-sharp steel blade is ground so finely that the very edge becomes a ‘wire’. It’s a fine curl of a burr that needs to be bent back and forth until the ‘wire-edge’ is so brittle, that it fatigues to the point of breaking loose. That is the absolute sharpest that your knife can be made. To reach that point, use the same technique as above, but on leather. Ten strokes, each side. Repeat as necessary.
- Carborundum/Coarse Stone
- After using your knife, return to the diamond stone and/or the homemade hone as necessary. Some say that every time you use your knife (let’s call it after a day in the woods) you should resharpen. Some say that if you take care of your knife, it shouldn’t need regular resharpening. You decide. But raise the bar on your standard of sharpness and you’ll never be disappointed.
Step 8 – Add a Handle
The main reasons for adding a handle to a knife blade are for leverage/power/applicability and comfort. Depending on the blade you’ve made (and the resources & tools you have available), you can choose from a number of options.
- Cord-wrap – My favorite, quick grip for a hacksaw (or other scrap steel) knife is a wrap of bank line, or other thin, readily-available synthetic cord. It takes the bite out of the metal’s edges and, in a pinch, can provide you with a few feet to yards of precious cordage. You can use any sort of macrame/Ranger/ladder-weave technique, but I prefer a simple spiral wrap with a self-constricting knot thrown in at the beginning. It’s all you need.
- Wood – You can split a stick of handle-size and insert the blade. Lash it tightly and you’ve got a hafted knife. For more strength, carve out the shape of the tang (part of the knife that extends into the handle) in the handle, which will gain you more surface area contact. Add some pine pitch glue and lash tightly with synthetic or natural cordage. (You can even make a simple wooden sheath by splitting a stick and making a relief carving of the blade into the stick, then lashing it back together.)
- Knife Handle ‘Scales’ – For a proper, full-tang knife handle, you may want to consider slapping ‘scales’ on both sides. At Gone Feral, this is more common for our thicker, heavier knives like those made from files. Make them out of wood, antler, bone, synthetic material, etc. Ideally, create slightly larger/thicker scales than needed and drill holes through both scales and the tang. Epoxy/peg them in place and then file/grind to your desired shape.
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