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I am in a metal workshop class. Many (practically all) the students in there are interested in making a knife, but are not very informed and are often misguided. I wrote up a general guideline to help them get along.
What do you think? Have I included anything vague or wrong? Are there things I should change? Thanks for your time.
-Don
This serves to help you make your first knife without too much confusion and chaos. We're sticking to plain and simple. If you choose otherwise, you will probably regret it. This is not a step-by-step how-to, but more of a guideline on good ideas and bad ideas, and why.
Plan
Do a little bit of planning. This can and probably will include research. Keep things simple. Choose and draw a design, decide on the finish and handle. I suggest not making anything too long or too thin; short and rigid is better for our purposes. A small hunting knife is a great way to start off; simple design, short, rigid, straightforward handle and assembly.
Another thing to note is steel choice. If you are money challenged, I encourage you to use leaf or coil springs, which you can get a lot of for just $10 or so. Leaf and coil spring are usually 5160, a good, tough, simple to shape and harden steel.
You CAN use files, but I recommend not due to several reasons: only some files are truly high carbon steel. Many files made today are just mild steel that are case hardened (only hard on the surface). Good files are hypereutectoid steels, meaning they have excess carbon, meaning that it requires advanced and PRECISE temperature control for heat treating. If you are dead set on a file (look for old Nicholson files), check to see if it is hardenable. Heat it to non-magnetic (red, NOT yellow), and quench it in warm oil (Canola). Use files to test if hard; if the files bite and remove metal easily, it isn't hard. If the file skates over like glass, it's hard. If the file did not get hard, harden again using the same process. If you get the same results, requench in WARM water. If it doesn't work, you've likely got mild steel.
My personal suggestion is to start out with steel of known composition right off the bat (meaning, from a steel supplier). I highly, and mean HIGHLY, suggest 1084. It's tough, and has enough carbon to take a great edge, but not too much that makes it complicated to heat treat. It's also very affordable compared to some other steels (and likely, files). 1084 is widely accepted as the most reasonable choice for inexperience or sub-par equipment due to it's exceptionally simple heat treat. This does NOT mean that it makes a sub-par knife, as it CAN make a great knife if done right. O1 is another great choice, although you have to be a bit more precise in some aspects, and it's usually a little more costly. Again, 5160 is another good choice (especially for a tough knife). My absolute favorite supplier is Aldo at http://njsteelbaron.com ; his 1084 is even modified just a tiny bit to make it even more forgiving during the heat treat. He's just a great person.
Forging
Forging is entirely your choice. Do note that with the forges at school, they build a thick layer of scale. Take this into consideration, especially if you're grinding. You may want to leave your forged knives a little thicker because of this, which brings me to another point: DON'T forge or grind your blade too thin before heat treating. You will regret it. Also don't leave your blades in the forge and leave them there for too long; they will burn up and become useless.
One last consideration during forging. Steel has a grain structure, and for the most part, a smaller grain structure is better. This structure is dependent on temperature. The greater the temperature, the larger the grain structure. For the final heats during forging, it is preferable to use a lower temperature (red) rather than yellow. We will normalize the blade later, but this is a good step to include to avoid any mishaps with the heat treatment later on. Preferably, we will anneal after the forging to make grinding/shaping the blade easier and faster (do NOT anneal a file with this procedure). Get the blade to a light red (RIGHT as you approach non-magnetic) and put in vermiculite. Come back the next day.
Make sure your blade is as even and straight as possible. The more you forge, the less you may need to grind.
Grinding/Drilling/Filing
Now we remove metal. We're aiming to finish up to 90% of the blade shape right now. This includes, for the most part: flatten, profile, bevel, drill. Please do not use large, thick gloves; tighter, thin gloves if you really have to. Wear a respirator, at the very very least, a dust mask. Use a dull, coarse belt to remove the scale, or an angle grinder of your blade is hefty. Scale will dull a fresh belt practically instantly. Use a fresh coarse belt for this stage. Flatten out the blade. Cut out the profile with the band saw or grind it down. Drill holes for pins if needed (if you try to drill after the blade is hardened, you will likely destroy drill bits).
Grind in the bevels. This is one of the most difficult parts of knife making. There are no secrets or short-cuts, jigs excluded. Practice is key here. Good tips to consider: grind with the edge up and take a full pass rather than sections at a time. Keep your hands steady and the angle locked. Use one hand for pressure and one hand for guiding the angle. Work on the plunge line last. Dip into water as needed to keep the blade cool (heat not considered as much during this stage; keeping the blade cool is just to prevent your hands from burning). Grind the bevel until the edge is about as thick as a quarter.
Heat Treating
Now we get to harden the blade. First we have to normalize (one of the most important parts to heat treating a blade). Heat the blade to non-magnetic and leave in still air to cool until there is no color; the cooler the better. If the blade warps after normalizing, straighten, then re-normalize. Repeat this process at least two times, or until the blade stops warping from normalizing. Make sure you do NOT overheat. What this process does is relieve any internal stress the steel has from forging and hammering, and also reduces the grain size. Most warps will be lessened or even prevented by simply normalizing.
On to hardening. Get the oil warm (we won't use water/brine due to complications); heat a scrap piece of metal and quench in the oil. Heat the blade a bit past non-magnetic (JUST a bit), and quench in warm canola oil. Agitate (meaning move) back and forth or up and down, but not side to side. One of the most difficult aspects of hardening is getting an even heat; draw the blade through the forge repeatedly to get more even heat, or use a muffle (hollow metal pipe, kind of like an oven inside of the forge). Don't leave the blade laying flat horizontally in the forge. If the blade is successfully hardened, then we now temper (as quickly as possible). If we ran into some problems, we may need to consider other options.
If it didn't get hard, we may need to re-quench again. If we ALSO encountered some warps, we will start back with normalizing. If the blade got hard but warped, the warp may be able to be fixed later (during tempering). If the blade got hard but warped substantially, we may need to go back to normalizing and re-quench.
Common mistakes during hardening:
Blade too thin (Uneven grind/profile)
Not normalizing
Too hot
Uneven heat
Cold oil
No, or improper, agitation
After the blade is hard, including if we have a slight warp, we temper the blade at a certain temperature for at least one hour, twice. This relieves the major stress on the steel from quenching. 450 degrees Fahrenheit is a good temperature. Lower than that will give a harder, but more brittle blade (400 is ok for a harder blade). Higher than that will give you less hardness, but more toughness. It's a good idea to check temperature with, at the very least, an oven thermometer.
For slight warps, straighten the blade while it is at tempering temperature. Using a vice, jig, or wooden mallet on a stump will work. I advise against a hammer on an anvil for the chance that it might cause damage. We straighten at tempering temperature because the steel is slightly easier to manipulate when hotter. Another method of straightening is tempering the blade while it is clamped straight (or shimmed in the other direction for more pronounced warps).
Finishing
Now we finish with our grinding and shaping. Make sure you use a fresh belt, as this minimizes heat. Dip the blade in water every few passes, to prevent our hands from burning AND to prevent overheating and ruining the temper. We don't want to get the blade over 400 degrees Fahrenheit. If the blade turns blue or gray (oxidation), it has gotten too hot, and you may have to grind that part off. The blade can turn yellow and even brown, but blue is too hot. Keep note that the more you grind, the less you may need to sand. Make sure there are no major scratches or gouges. Don't sharpen the knife at this point, unless if you have decided that it's finished.
Now we can sand, if you'd like. A hand-sanded finish can look and feel cleaner than a ground finish. There are other options, such as sand blasting, painting, etc, but we will touch on none of those. Keep the blade secure in a vise and start out with a coarse grit. Use a backing surface, such as metal, wood, or rubber. A metal backing surface will maintain clean sharp edges. Remove all scratches from the grinder, and be careful not to slice yourself on the edge. Progress up in finer grits, sanding in one direction only as you are finishing. Don't leave any scratches from previous grits. Water can be used with higher grits as well.
After the blade has been sanded, we can attach the handle. I won't cover handle assembly, but I will cover some basic tips. Tape up the blade when working on the handle; this prevents scratching, and also cutting yourself. Before epoxying the handle to the blade, make sure the tang is flat and the sides of the scales are flat (if you are doing a full-tang with scales handle; hidden tang and other types are not covered). Scratch up the tang with coarse sandpaper for better epoxy hold. Don't forget to clean and finish the front of the scales before epoxying, as it's much more difficult to work on that part once it's attached. Clean the tang with acetone and if possible, denatured alcohol afterward; this cleans out any oil that can prevent the epoxy from holding properly. When you epoxy the handle, don't clamp too tight, squeezing all the epoxy out. Clean up the epoxy at the front of the scales with acetone (using a q-tip, cotton ball, etc).
What do you think? Have I included anything vague or wrong? Are there things I should change? Thanks for your time.
-Don
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