One of the biggest advantages of forging your own knife is the personality you can infuse in it. Sure, you could buy a knife that’ll be just about as good as a hand-forged knife, but it won’t have any character. It’ll also probably cost a lot more than your own creation would – especially if you use scrap metals to forge. So what is the best scrap metal to use for knife making?
The good thing about metals (and steel in particular) is that despite whatever form they previously took once they are heated, they can be reshaped, given an edge and more. Smaller but thick steel can be pounded down to a wider, flatter knife shape with enough work. This means that a surprising number of “scrap” metals can be used for knife forging – and bring their stories along with them.
What Makes a Metal Good for Knife Making?
The ideal type of metal for your knife or blade depends on what you plan to use it for. For hatchets, machetes, and other blades that have to withstand impacts, you want a tougher and stronger metal that won’t fracture. For finer knives that emphasize cutting, you’ll want something strong and hard, but it won’t face much impact, so it doesn’t need to be as tough.
When it comes to determining the strength, hardness, and toughness of your knife, the carbon content plays a major role. In steels with higher carbon content, the metal is going to be harder and stronger because it helps hold the iron atoms in place. However, if there is too much carbon it becomes brittle and you risk fracturing with any impact.
Overall, the ideal knife will have the right percentage of carbon and other alloys to perform what it was made to do effectively without risking breaking or other damage.
What to Look for in Potential Scrap
When looking through your local junkyard or workshop for scrap, you’ll want to keep an eye out for anything that was regularly put under strain. This is because the steel used in these scrap items would need a higher percentage of carbon to be able to withstand pushing and pulling, but a low enough carbon content so that it is not brittle enough to fracture outright. In many cases, this carbon content is great for all-purpose knives and shouldn’t give you too much trouble when it comes to forging.
Additionally, you’ll need to consider the size of the scrap you’re going to use. If you plan to make a 6-inch blade, you need something of a similar size because although you can hammer the steel to various shapes, you cannot suddenly make more appear to fit your project. Fortunately, you can always cut a piece off of a bigger piece to make a smaller knife, which is why many scrap knives are smaller.
You can also perform some basic tests on the scrap you come across, such as scratching the material to determine the hardness, trying to bend it to test strength, or smacking it into something to test toughness. If there is a fracture or other serious damage sustained, it probably won’t last through the forging process.
2 Ways to Test Scrap Metals
Harden then break a small piece
Take a small piece and heat it till it is no longer magnetic (that’s a very general way to know you got it hot enough) then quench it in oil to harden it. many common metals used in knife making are oil quenchable so it’s a good place to start.
Take your quenched and cooled piece and put in a vice then smack the side of the piece hard with your hammer. If it is hardenable steel it will break rather than bend. If it bends either it’s low carbon steel or it’s a water quenching steel. Try the same heat then quench process but use water this time. If the piece still bends it’s no good for knives since it won’t hold an edge.
By taking a piece of your mystery metal and touching it to your grinding wheel you can judge the carbon content by the color and shape of the sparks. It is FAR easier to understand with a video than in words so give this quick (just over 1 minute) video a watch.
Pretty straight forward, right?
Common Scrap to Forge With
Below are some of the more viable scrap pieces to consider for your home forging. Depending on your plans for the blade, some may work better than others but if you’re able to get one, it’s hard to go wrong. Just aim for older pieces of steel as they don’t make things like they used to, with older steel being higher quality overall.
At first glance, a spring may not seem like it could possibly be a knife because it is round and coiled. However, a coil is just metal wrapped around something so if you unwrap it, it becomes just a cylindrical piece of steel that can be worked like anything else. Whether you plan on breaking a piece off or unravelling the whole thing, all it takes is some extreme heat and elbow grease to have the beginnings of your new knife.
Leaf springs off an old truck are generally excellent steel for blade making. You will need to anneal them, like most found steel, but they have to bonus of being in nice flat wide bars already so its less work on the anvil to get them into a knife-like shape.
If you happen to be lucky enough to find elevator cable, you could be in for a unique knife-forging experience. Like the coiled spring, steel cable is braided steel just asking to be separated and reused for one or more knives. The tension the cable is built to stand up to means it has a higher carbon percentage, so it is strong and great for knife forging.
Circular Saw Blade
Saw blades are sharp, but they can be sharper! While you won’t use the entire saw blade for a single knife, cutting a small section out from the blade would allow you to forge a decently sized knife made of very hard and edge-holding steel – as long as you find an older blade. Newer blades may not have the same chemical makeup with less strength, making them sharper but struggling to hold their shape.
Railroad spikes are already scary as is, but when you sharpen the spike at the bottom into a blade, you’re talking about a unique knife that looks as dangerous as it is. Railroad spikes are made of stronger, more carbon-rich steel which makes them more suited towards hardness, durability, and strength than sharpness because they needed to resist the impacts of hammering when laid on tracks. Meaning they won’t have great edge retention compared to some other steels.
A railroad spike is also usually the perfect size to fit in your hand, and the large tang you can leave allows for more custom metalwork, engraving, and other unique additions to make it stand out.
Perhaps the most popular first knife scrap metal, the old school steel file is a great way to make a small but incredibly sharp blade that fits in your hand. These files are made to be very hard – which isn’t ideal for knife making – but can be annealed to soften the steel so that it can be better shaped before you reharden it. After shaping and annealing, you’ll have a versatile piece of steel that will be hard, hold an edge well, and make a great knife.
If I was starting out again and wanted to try my hand at a few knives I would save myself the trouble of finding metal then testing and shaping it into what might not end up being useful as a blade. This option wasn’t around when I started or I would have gone this route.
IMO the best scrap metal for knife making is not scrap metal at all. You can order 1095 high carbon steel billets from amazon for amazingly cheap. The fact that if you have prime you can get that heavy steel shipped for free is just icing on the cake since that is what usually kills you when ordering steel online.
Heres an example off amazon:
If you aren’t familiar with 1095 steel it is a favorite of knife makers and reasonably easy to work on an anvil making it a great choice when starting out. Here is a very brief rundown of how to heat and use 1095 high carbon steel.
Forging: heat to 2100°F (1150°C) . Do not forge below 1500°F (815°C).
Normalizing: Heat to 1575°F (855°C). Air cool.
Annealing: Heat to 1475°F (800°C). Furnace cool to 1200°F (650°C) at a rate not exceeding 50°F (28°C) per hour. Alternately bury it in sand or even the ground to cool for several hours. I often will toss it in a campfire and dig it out in the morning.
Hardening: Austenitize- Heat to 1475°F (800°C). Thicker sections can be quenched in water or brine with extreme care but can also be oil quenched in sections under 1/4 in. (6.35 mm) thick as the preferred method.
Tempering: The quenched hardness should be approximately 66 HRC. Hardness can be adjusted downward by proper tempering.
|Tempering Temperature||Rockwell Hardness|
In the end, making a knife from scrap metal is a cost-effective way to forge for fun. Not knowing the specific chemical composition of the metals you use adds a bit of guesswork to certain things like the ideal temperature and treatment method, but as long as you don’t mind it being a bit rough around the edges, scrap metal can be used to make a perfectly good knife.
You’ll want to look for high-carbon steel scrap that is built to be hard but not brittle like springs or cables for the most versatile option, or stronger pieces like railroad spikes if you’re going for something with a little more impact.
Overall, if you’re making the knife for yourself it’s hard to go wrong with any of our scrap recommendations. Some will work better than others for what you’re trying to do, but as long as you enjoy the process, that’s the fun of knife forging.