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How to Make a Knife From a File

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Stacy E. Apelt - Bladesmith, Dec 14, 2011.

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  1. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    This is a basic tutorial for making a knife from a file. The process of knifemaking is discussed in many of the other stickies, and this tutorial will only deal with the basics. For more detailed info on making your first knives, see the sticky, "How to Instructions for Making a Knife". For details on annealing and heat treatment, see the HT and metallurgy stickies. Shop safety should always be observed, especially eye protection when grinding.

    Often asked question - Can I Make a Knife From a File?

    You can make a knife from anything that is hard enough to be sharp….but the quality will vary.
    You can make a knife from things found in your garage, like old lawnmower blades, car springs, saw blades, and FILES.

    Of these , a file is probably the only one that will make a decent knife.

    The problem with any “found” steel is that you don’t know what it is made from. Not all steel is blade steel. For a knife blade you need a steel with enough carbon to harden, and a few other attributes. Since a file is made from high carbon steel, and is already hardened, that makes it good knife steel - Right? Well, maybe and maybe not. That is the problem when a new maker wants to use a file to make a knife. He won’t know which it is. A smith with years of experience will know quickly, but the Newbie may waste a weeks work and materials to get a knife that either breaks, or won’t hold an edge.

    OK, lets talk files_
    A GOOD file is made from steel with about 1% carbon, and a little manganese. A small bit of Tungsten, Vanadium, and Chromium is added to that to make the file harder and the grain finer.
    This mix can make a good knife blade.
    However, some files are only case hardened mild steel, and underneath the hard teeth is soft un-hardenable steel. Quality brand files, like a Nicholson File, will be hard steel all the way through. Notice how I say “Hard Steel”? A file is made to cut away metal, so it needs to be made very hard. Most files are hardened in the mid to upper 60’s on the Rockwell scale. This is way too hard for a knife blade. The trade-off with hardness is brittleness. A hard steel breaks easily. Most of us have broken a file by using it as a prying tool. They don’t bend - they break. There are ways to deal with this problem, which we will cover shortly.

    What is the best way to go for making a knife?
    The short answer is to use a known steel and one that is easy to work with and heat treat. For new smiths, and those with limited equipment, 1084 is the best choice.
    It is a simple steel that heat treats easily.
    As an experienced maker ,I recommend that you stop reading at this point and look in the stickys and at the many knife making threads. They deal with making a knife from a known steel.

    For those who still want to make a knife from a file.
    Start with a good quality file, like a Nicholson. It can be old, rusty, and have worn out teeth….as long as it is high carbon steel.
    Now, you need to decide how you will be making your knife. A file will have to be softened to make it possible to convert to a knife. There are two options here:
    1) Make your knife from a hard file - Use the file almost as is to make a simple knife. It surely won’t be fancy, and may be little more than a prison shank, but it is the simplest method to make a file knife. More on this later.

    2) Soften the steel by annealing it, and then make the knife with files and sandpaper. Once shaped, the steel is re-hardened. This makes a better knife, but saves nothing over using a piece of 1084 to start with. It actually adds some steps.

    To anneal a file, it has to be heated to above 1350°F. The way to know it is that hot is that a magnet stops sticking to steel at that temperature. Use a torch to evenly heat the file, and when a magnet stops sticking to the metal, try and keep it at that color red, or a tad more red, for about two or three minutes. Once “soaked” at 1350-1450°F, it is allowed to cool off in the air until the red color is just about gone. Lowering the lights can help with seeing this. At the last dull red glow, quench the file in a gallon or two of canola oil. This will leave the file in a softened state. Check it with a good file, and it should be easily filed. If that works, the steel is annealed and ready to be cut, ground, filed, sanded, etc. into a knife. We will stop here for this process, as it is the same for any knife making. See the sticky, “How to Instructions for Making a Knife”.
    A word on annealing - You often see suggestions to heat the file in a camp fire, BBQ grill, or with a torch, and then to bury it in ashes or vermiculite overnight. That will anneal a lower carbon steel just fine. But, for a high carbon file, it can create a hard form of pearlite that will give you problems later. The oil quench after the steel is cooled down to about 900°F is a much better method for higher carbon content steels. Save the canola oil to use again when re-hardening the blade in HT.

    [U]OK, If you are still reading - lets make a file knife ![/U]
    A Nicholson File.
    A grinder or sander of some sort to remove the hard steel.
    A stack of Wet-or-Dry sandpaper from 100 grit to 400 grit.
    About six feet of paracord, some epoxy, a sharpening stone.
    A bucket or tub of water to dip the file in for cooling.
    A place to work.

    The file is too hard and brittle to grind as is, so it needs to be made softer and less brittle, but left hard enough to be a knife. This is done by tempering. The file is placed in the kitchen oven at 450°F and baked for two hours. It is removed ( careful, its hot!) and quenched in running water in the sink. Once cooled off to room temperature, dry it and put it back in the oven for another two hours. When done baking the second temper cycle, cool it down with water again, and it is now ready to make into a knife. It should be around Rockwell 58-59 in hardness, and tough enough to not break easily.

    Go to the sander/ grinder and start shaping the profile. Use bare hands, and when you notice the file getting hot, dip it in the bucket of water . The file must be kept below 450°F or the temper will be ruined, and the edge will be too soft. If the area being ground turns blue, that is bad, so avoid it at all costs. One or two blue spots durring the grinding will not ruin the knife, but too much, especially in the final grinding will make the blade have soft spots on the edge. You will only get a little grinding done between dipping the blade in water. The process will be wet and messy, so wear old clothes, and toss an old towel on the floor.

    Once the profile is shaped, start shaping the bevels. After the knife starts looking like you want, refine the shape and surfaces as smooth as your equipment allows. Again, never let the blade get hot while grinding.

    Once the file is shaped into a rough knife blade, the real work starts. Clamp the knife to a board with the edge along the board edge. Start sanding the blade with 100 grit sand paper and a hardwood block to back the paper. Frequently dipping the sanding block in water with a little dish soap added will make the sanding faster and smoother. Do both sides and all surfaces until it is smooth and well shaped. The edge should be a small flat line, about .020-.030“, and not sharp yet.
    Change to 220 grit paper and repeat. Switch to 400 grit and clean up all surfaces so they are smooth and have a nice satin finish. The edge should be almost sharp now, about .005 -.010“ wide. All that is left is to sharpen the blade on a sharpening stone. Once sharp, clean the blade up, and tape the edge well. The blade is now ready for a handle.

    Now lets put a paracord handle on it.

    Take about four feet of paracord and tie an overhand knot on the front part of the handle, where it meets the blade. This area is called the ricasso. Cut the tail end so it comes about 1” from the butt of the handle. Mix some epoxy and put a small line down the center of the tang, and set the paracord tail in this bead of epoxy. Let dry. This locks the tail in place down the center of the wrap. The tail should stop about ¼” from where you want the handle wrap to stop.
    Take one foot of paracord and pull the core out to make it softer. Make a loop from this , and lay it on the opposite side from the glued down tail. The loop should stick just past the butt, and the two ends should stick out along the blade. The two ends should be going OVER the knot you just tied. Use tape to hold the loop in place. The tape should be at the very end of the handle, and on the blade at the ricasso, next to the overhand knot. Don't put any tape where the handle wrap will be.
    Start tying overhand knots down the tang. Pull each tight and align the cross-over places directly over the glued down tail. Don’t worry about the loop side, you are going to pull the loop out soon. Just make the wraps tight and neat over the loop.
    When you get to the tail end, tie one more knot past the tail.
    Un-tape the loop and the ends at the ricasso.
    Tie another overhand knot, with the cross-over part over the loop on the other side. Cut the wrap cord end so there is about 12” of extra cord . Stick the end through the loop, making sure there is 6“ of loose cord on each side of the loop . Grab the ends of the loop cord ( vise grips may help) and pull the end out under the wrap. Snug everything up. And when all is right, cut the cord where it comes out between the wraps. Tuck it back down with a screwdriver if needed.
    This completes the wrap, but to make it more robust, lets epoxy fill it.
    Mix up a good batch of slow cure epoxy. 24 hour type is best, but one hour will work. If you can get a thin epoxy, that is the very best type. The clear coat and bar top epoxies are superb for this task. If not available, thin the epoxy you have with a little acetone or epoxy thinner. If thinning the epoxy, it is best to test it out by mixing up a small amount and letting it dry. If it stays gummy, the thinner you are using won’t work, or you used too much. Once sure the epoxy will cure, use a bristle flux brush to dab the epoxy into the paracord. Let it soak in and don’t get too much on. You want just enough to make the cord look “wet”. Wipe off any excess and hang the knife point up to dry. Check when the mixing cup of epoxy is just starting to set up and wipe off any drips off the knife butt with a cloth ( not a paper towel) wetted with acetone. An old tee-shirt is best for this. You don’t want anything with lint or fuzz.
    Let the epoxy cure for 24 hours.

    Your file knife is done - go cut some stuff with it.
    Michael Olson likes this.
  2. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    The following is a tutorial from Tai Goo:

    Here’s a very simplified version of making a knife blade from a file… not the only way or the best, but should give satisfactory results for newbies and help establish a starting point.

    #1. Get a suitable Nicholson file.

    #2. Soften the file for stock reduction by taking it up to a black heat (day light in the shade) holding it there for a minute or two and then let it air cool. If you start to see even the faintest glow, take it out of the fire until it goes away and then go right back in. Repeat this process several times at any point prior to hardening, if necessary.

    #3. Grind or file off the teeth (especially along the edge).

    #4. Grind or file the blade to shape.

    #5. Sand the blade to 100 grit parallel to the edge.

    #6. To harden the blade, take it up to non magnetic, plus 50-100 degrees,… usually “cherry red” (daylight in the shade). Hold it there for a few minutes and quench it in fresh warm vegetable oil.

    #7. Go immediately to the temper while the blade is still warm to the touch. Temper at 400 - 450 for an hour, (use a good oven thermometer) allow to cool to room temp., and repeat 2-3 times.

    #8. Clean the blade off with sandpaper or a water stone.

    #9. Sharpen the blade.
    Last edited: Dec 15, 2011
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