Introduction: Japanese Style Blade Forging
So, before we start, I'd like to try and answer a quick question that a lot of people have: Why is forging better than stock removal?
For those of you that don't know, stock removal is a way of creating a knife that involves removing material from a piece of steel until a knife shape is revealed. Forging is the process of creating a knife where the steel is heated then moved by repeated hammering, until it is in the shape of a knife.
So why forge when you can use stock removal?
1) Steel waste: Stock removal requires lots of cutting and grinding. All the steel that is removed ends up becoming waste material, and is thrown away. With forging, I can often make a blade using ~70% the steel that would be needed for stock removal. This lowers costs, and is just in general less wasteful
2) Shape of the blade: One of the biggest differences I see between stock removal blades and forged blades is the distal taper. Distal taper is basically a smooth taper from the the thick part of the blade to the thin tip. It is very difficult to put in an accurate distal taper with a grinder. Most stock removal blades end up being the same thickness along the entire spine then suddenly decrease in thickness at the tip. Forged blades can have a smooth distal taper easily forged in, which increases the blade's balance and cutting ability.
3) Larger blades: Stock removal is great for making small blades, but what happens if you ever want to make something big? Stock removal simply doesn't scale up as well as forging does.
4) Tools and money: A good belt grinder can easily cost in excess of $1500. Most beginning knife makers can't afford this. Although a forge may seem inaccessible, they are actually rather easy to build and can be built cheaply. I built my forge for a little under $200 dollars, and still ended up with enough material to potentially build a second one
5) Forging is fun!: Forging is actually really fun and interesting to do! I have nothing against people who use stock removal methods, but I think you should at least try forging once. You may find that you really enjoy it!
Also, a quick note. This is Japanese STYLED forging. Traditionally, Japanese blades were made by forge welding a type of raw steel together called tamahagane. This process, however, is currently well outside the resources I have at my disposal. Basically, this instructable will cover the basic hammer, beveling, and shaping techniques used to create Japanese blades, but instead will use modern steel as the blade material.
Sorry for the long winded introduction, now onto the forging!
Step 1: Materials and Tools
I will be forging an ~9 inch long tanto. The thickness is ~1/8 inch (this is unusually thin for a tanto, but thinner material is easier to work. I recommend this thickness for beginners). If you want to make a larger blade, you will have to scale up the size of the material appropriately.
Materials and tools:
*7"×1/8"×5/4" piece of shallow hardening steel (1070, 1095, w1, w2, etc). I used 1095 for this one
*Some form of anvil
*Square hammer, ~3 lbs
*Cross peen hammer, ~2-3 lbs. Not required, but very helpful.
*Spray bottle with water. More on this later
*Bucket of water. (for cooling tongs and emergencies)
*Forge of some sort
*Safety equipment (gloves, apron, safety goggles, etc)
Step 2: Cutting and Prepping Material
This part is pretty simple. Mark an approximately 7" length of steel. If you want a larger or smaller blade, mark a length that is ~70-80% less than your desired final length. During forging, the material will be stretched quite a bit, and your blade will grow by a pretty large margin. The thicker the material is when it starts, the more it will stretch.
When you have marked your steel, clamp it in a vice and cut along the marking with a hacksaw. After it is cut, I file off the burrs and slightly round the edges. This is just a personal preference and isn't required. I find that it helps prevent inclusions from being forged in later.
Step 3: Sunobe: Part 1, the Nakago
To start the form of the blade you have to forge the sunobe. Sunobe is basically the process of creating all the necessary tapers and drawing certain portions out. Sunobe is done on both the nagasa (blade and tip portion of a knife) and the nakago (tang portion), but I always start with the nakago.
Quick note: I have numbered the pictures for convenience and will be referring to the numbers often in my explanations.
To begin, start your forge up. You will also need your tongs, anvil, hammers, and water out. Once the forge is up to heat, place the metal in the forge, nakago first. While you are waiting, take your spray bottle and put a layer of water on the face of your anvil, like in picture 9. This may seem counter intuitive, but it is a technique called water forging. The steam that is created when the blade touches the anvil will blow off excess scale and oxidation, saving you work in the long run. Now wait for the metal to heat. You will know the metal is fully heated when its color becomes the same as the surrounding forge. At this point, the metal should be around 2000°-2100° F, which looks to me like a bright lemon color. Too hot, and your metal will be sparking and oxidizing rapidly. Too cold, and you won't get very much time to work the metal and it won't move very much.
Once the metal is up to heat, grab the side that is facing towards you with the tongs. Set the metal so the edge (not the face) is resting on the anvil, like in picture 6. Begin to hammer in the direction and placement that the arrows designate in picture 6. Make sure you are working both sides of the metal evenly, by turning the blade 180° every few hammer strikes. Once your metal dulls to a dark red, put it back in the forge. The idea here is to slightly round and taper the very end of the nakago. It should begin to look like picture 7.
Once you've got your nakago looking similiar to picture 7, pull out your cross peen hammer. Again, place the metal so the edge rests on the anvil. begin to hammer with the cross peen perpendicular to the edge of the nakago. Make sure to work both sides evenly. This should put some tiny bumpy waves in the nakago, like in picture 8. Take your flat hammer and begin to hammer the waves flat. This will cause the nakago to stretch lengthwise, a process called "drawing out". Keep alternating with a cross peen and flat hammer until you've got the nakago slightly shorter than what you want. Make sure you are replenishing the water on your anvil in between heats.
Once your nakago looks somewhat similar to picture 10, you can hammer in the machi. The machi are the two slight divots at the very base of the tang that the habaki will eventually rest on. I have arrows pointing to them in picture 11. To hammer in the machi, simply place where you want the machi to be on the edge of the anvil and tap directly above it, then repeat for the opposite side. This process is shown in picture 13.
At this point, the nakago is around 3 inches long and tapered slightly, as seen in picture 14. However, you can see in picture 12 that all the hammering has caused the nakago to thicken. This is where a distal taper, or tapering of thickness comes in. Having a distal taper in the nakago is essential for it to be able to have a habaki and tsuka (mountings) put on later. To do this, start by resting the face of the metal on the anvil. Take the flat hammer, and start lightly tapping near the base of the nakago. Gradually move your hammer down the nakago, and gradually increase the strength with which you strike the steel. In picture 15, the blue dots represent where my hammer is striking, and the size of the dots represent the force behind the strike. Keep repeating this, making sure to work both faces evenly. In 16, you can see the start of a taper develop. In 17, the taper has become more defined and the machi are now the thickest part of the nakago. 18 shows how Smooth the metal should look (no large dents), and in 19 the taper is complete. This has caused the metal to stretch quite a bit, and my nakago is now just under 4", as shown in 20.
You now should be ready to move onto forging the sunobe in the nagasa.
Step 4: Sunobe: Part 2, the Nagasa
The sunobe for the nagasa mainly consists of forming the basic shape of the kissaki (tip of knife) and forging in a distal taper down the blade.
To start, flip the knife around and use the tongs to grab it by the nakago. Place it tip first in the forge, with the nakago facing you. Make sure that you keep your anvil face wet.
Once the metal comes to heat, pull it out by the nakago and place the metal so the edge is on the anvil. Then, very similarly to how the nakago was started, start to round off the very tip, striking according to the arrows in picture 3. Here's where the process starts to differ. Instead of stopping when the tip is rounded, continue hammering the tip until it is pointed and a centered triangular shape. pictures 4-8 show the formation of the point in the tip heat by heat.
In picture 9, you'll notice that the tip has now become very thick. So to correct this I hammer a distal taper into the tip and down the blade. In picture 10, the dots show the position of my hammer strikes for the distal taper, and the size of the dots corresponds to the force behind the strike. It is very important that you work both sides evenly. During this process, the tip may become rounded off. Hammer it back into a sharp tip like in picture 12 if this happens.
Once you've got the sharp triangular tip and a distal taper, move on to the next step.
Step 5: Beveling the Nagasa
To bevel the nagasa, set the face of the blade on the anvil. Choose a side that will become your edge. Beginning at the tip, strike according to the blue dots in picture 1. Your tip should start to naturally curve backwards towards the spine. The thicker the material, the more curved it will become during beveling. The metal that I was using was too thin for the tip to curve into place with beveling alone, so I set the spine of the blade on the anvil and begin to lightly tap the tip into place. Picture 2 shows where I struck the metal in order to get a flat spine. Once the spine is straight, you can begin to move down and bevel the rest of the nagasa. Picture 4 shows where to strike along the blade. Make sure to work both faces of the blade evenly, or your edge won't be perfectly aligned in the end. Also, you should still be wetting the face of your anvil to blow off the scale that your knife has accumulated. When you bevel the blade, it may curve backwards during the process. If this happens, set the spine of the blade on the anvil face again and lightly tap the edge in order to straighten the blade. pictures 5 and 6 illustrate this. Once the entire edge has been brought to a little under the thickness of a dime, the beveling is basically complete. Sight down the length of your blade to check if it's straight. Correct any slight warps in the straightness of the blade, then move onto the next step.
Step 6: Beveling the Nakago
For this style of blade, the Nakago must also be beveled. Picture 1 shows where I strike the blade with my hammer to get a bevel. Make sure to work both faces evenly. The Nakago may curl slightly upwards during this process, whether you leave that in or not is up to personal preference. I personally like to have the Nakago curl upwards very slightly, so I left it in.
Once the Nakago hs been fully beveled, sight down the blade to see if it is straight. At this point, I usually heat the blade up, take it to the mini vice anvil, and just lightly tap up and down the whole length of the blade, on both sides. The purpose of this is to smooth the surface and promote blade straightness and edge alignment.
Step 7: Finished
At this point, the blade should very closely resemble what you want the final shape of your blade to be. From this point on the rest of the shaping will be done with a sander and files.
Anyway, I hope you enjoyed and maybe learned something new! Forging is such a vast topic that there's no way I could have covered every single thing about it in a single instructable. So feel free to ask me questions or for clarification on any parts in the instructable. You can either post it in the comments or even shoot me an email at firstname.lastname@example.org
As for future instructables, here's what I have planned:
*Hamon and Heat Treatment of Japanese Blades
*Blade Polishing and Sharpening
*Water Casting Copper + Japanese Tsuba (Sword Guard)
Please tell me which of these you'd like to see next, and I'd love to hear other suggestions for instructables that I don't have in the list.
Thanks for reading!