Sword Forging Class

It was not without some trials and errors along the way. First, I had chosen 1050 medium carbon steel for the stock to work with and I was not that familiar with it. There are some good reasons for this choice of steel, first being that it has a TTT of about 3/4 of a second to get below the nose of the curve and therefore is very responsive to the clay coating applied to the back of the blade. In my earlier test blades, I was able to get a clear and dramatic hamon, but was not really happy with the softness of the back. If not properly hardened, the blades bent too easily, but I began the trip hoping to find the right combination to overcome that handicap. Another clear advantage of this steel was that it would stop an edge crack from propagating through the hamon and made the blade virtually indestructible.

Swords have a unique set of requirements and the right choice of steel must take these into account. In use the edge of the sword is likely to get chipped. Because the edge is under tension, once the integrity of the edge is broken, it will break quite easily. This can be demonstrated by chipping the edge with another piece of hardened steel and then striking the spine of the blade over the anvil. In my test pieces, 1050 would stop the crack and despite numerous hard blows to the spine the crack would travel no further than the hamon. I was also able to place the blade in a vise and bend it 90 degrees at the crack and back without it breaking. This showed me that the steel was capable of withstanding actual conditions.

Another requirement is that the edge be hard enough to cut through tissue, bone and even metal without chipping. Edge holding is not as important as it would be in a using knife, but if the edge is too soft it will not cut cleanly. Again my tests showed that the steel would get hard enough to perform well. I do not have a Rockwell tester, but from looking at the charts and by checking with a file, I estimated that it would fall into the 58-60 RC range.

Prior to the class, Chuck and I made several test blades attempting to solve the soft back problem. We converted one blade to banite and it would support the weight of two men, over six hundred pounds, without breaking, but we were unable to subsequently reharden the edge without softening the back too much again and it this condition it would not stop the fracture.

We also tried several methods of flash quenching in water, interrupted quenches, but still ended up with soft pearlite structure in the back. Finally we reduced the thickness of the clay to a minimum and quenched in water until all color had left the spine of the blade. This produced a hard edge and tough back, making a mix of pearlite and martensite in the area under the clay.

D. Fogg

Chuck Patrick (click image)

The Class

We had twelve students with twelve forges going at once. The shop was a converted milking parlor comprising one long open room with the forges going down each side and steel layout tables in the center. Each station had a coal forge, anvil, and post vise. There were a few gas forges available, but most of the students worked with the coal. When all the fires were lit and the hammers were beating on metal, it was a factory.

Forging swords

I demonstrated first, showing how to shape the point and begin the bevels. My technique involves working with a heavy hammer, minimum four pounds and preferably larger, and constraining motions by locking the hammer arm to the side and striking with the forearm and not wrist. Also the arm holding the work is locked into the side also and the piece is moved by rotating the hips. The hammer face should strike in the same spot and the work moved. Attention has to be paid to the height of the work piece so that it is flat on the anvil and the handle is not tipped up or down creating a bend in the blade which will later have to be straightened. In the manner of the Japanese, I like to wet forge. Wet forging is simply keeping the anvil face and hammer covered with water while forging. The water does not cool the blade but helps to blow off the scale and keep it from being beaten into the hot metal. Scale is uncompressible compared to hot metal and will leave craters in the finished work that can be a problem. I also like to keep the scaling down by working in a rich fire and at lower heats.

Forging steel is the beginning of the heat treating process and as much care should be given to the temperature of the steel as is given the actual forging. I like to progressively reduce my forging temperatures until in the finish forging I am working just above and below critical. I feel this goes a long way to refining the grain of the steel. Care must be taken not to drop too cold or stresses can be built into the steel and so you should cycle right around critical.

I like to work in small sections, beginning at the point and then forging the bevels by laying the unforged steel on the anvil and forging into the already forged section. If you try to forge from the already beveled area to the unforged area, the thicker unforged section will curve the blade every time and create problems. It is helpful to straighten and true the blade before it returns to the fire so that you don't end up chasing your lines and can start from a good straight line.

A common mistake is to fail to set the angle on the bevel by raising the bar up from the anvil. You have to set the angle otherwise the bevel will be establish on the hammered side and remain flat on the reverse. I found it helpful to work to your weak side first, setting the bevel and then switching sides. I need to make a sketch of this, but will have to add it later.

The forging proceeds down the blade in three or four inch segments, taking care to watch the lines and true everything up as you go. I do not attempt to forge to the final edge at this time, but rather want to establish the bevels and profile for the blade. It is important to forge equally on both sides. If you fail to do it, the blade will begin to twist because you are drawing more on one side than the other. Also, by forging equally on both sides balance the stresses on the blade.

Another common problem encountered is keep the blade from curving radically. The old adage about never beating on the edge is foolishness. You can beat on the edge without creating problems, but obviously you have to correct for any upsetting. I use the length of the anvil to take the curve out of the blade laying the section that is curving on the anvil and lightly tapping it back straight. When the edge is thinner, I use a wooden or rawhide mallet and a wooden block so I won't mar the blade or edge.

When you approach the tang end of the blade it is time to reverse your grip, you will know when it is time because it is too hot to handle comfortably. It is difficult to continue the bevel line from the forged section without running into the problem of the thicker section curving the thinner beveled area, at least for me, so I begin at the far end by forging the tang. On the katana, the bevel is just and extension of the blade bevel. The only consideration with the tang area is that it be tapered in all directions to the area where the fittings will seat to the blade. I don't go to great pains to set the notches just rough them in, but I do spend a considerable amount of time shaping the tang. The tang takes a lot of stress since it is fulcrum point for the blade and it is wise to make it as strong as possible and forging to shape is the best start.

Working back from the tang, forge into the blade and join the previously forged area. I like to let the blade cool at this point so I can handle it comfortably and look at it from all angles. It is amazing how different steel looks when it is cold from when it is hot. This will give you the opportunity to see where you need to work and to plan you finish forging.

When I begin to final forge the blade, I use the same hammer, but use lighter blows. I am looking to bring the metal down to the edge, straighten all the lines, crisp up the bevel lines and remove any hammer blemishes from the rough forging. It is slow and careful work, but will greatly shorten the finishing time when the blade is cold. The final shape of the blade is straight. The curve will be established during the hardening process.

As a final step to the forging process, I cycle the whole blade from critical temperature to below 1000F for at least three times in the air. This thermal cycling will reduce the stresses in the blade and help to further refine the grain structure before hardening. I do not anneal my steels and if they need to be further softened I will heat the blade to 1300F and hold for a long soak.

Handwork