forging

All posts tagged forging

I have been pretty busy forging, with the completion of a scimitar inspired knife out of a railroad spike, hardened in water, and a sort of tanto for my friend Phil who provided me with steel for a new anvil and helped me build it. The tanto was differentially hardened using the clay method with Satanite refractory cement and transmission fluid for the quench. But first, here is a photo of the scimitar (the handle is parkerized), sheath by Robert Jones:

Railroad Spike Scimitar

Railroad Spike Scimitar

Below is a photo of the parkerizing process for the handle, about ten minutes at 190F in the manganese bath:
Parkerizing

Parkerizing

The tanto was forged from a 1075 steel flat stock. I made one mistake in the claying process, and that was to heat-up the blade for quenching without letting the Satanite dry properly. this caused cracks in the covering, and uneven areas of hardness.
Tanto Steps

Tanto Steps

The objective of this operation is of course to obtain a very hard edge combined with a soft back. The result is a sharp blade that holds an edge but does not break easily. The quenching process was quite entertaining.
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The knife was tempered in the kitchen oven twice 1h30 at 450F to soften the metal a bit. 1075 quenched is too hard for a knife, the blade would chip too easily. The hardening succeeded, because the file I used to clean-up the blade would bite on the back of the blade, but skid right over the edge.

Next was polishing with sand-paper in the following grits: 100, 220, 400, 800, 1000. I could not remove all the file marks and some imperfections due to poor hammer technique (this being really my second completed knife), but the result is still pleasant. I did sharpen the edge, and it shaves nicely. For the handle, I used a piece of wood I had laying around, traced the contour of the blade on it and carved the inside with a narrow wood chisel.[warning]As much as the forge environment is dangerous, working with a wood chisel scared me quite a bit. I came close to gash my hand open with this tool, and I now have a lot of respect for it. Be VERY CAREFUL working with a chisel, trust me on that one…[/warning]

Carving handle

Carving handle

I had some PC-7 epoxy and decided to use it to glue the two sides together and fill any small void. The photo below was taken before I wiped the excess off. I will let it dry for 48Hrs before sanding down the handle to size.
Gluing the handle with epoxy

Gluing the handle with epoxy


I was going to wait before posting this last part of the series that I finished the handle, but I don’t seem to be able to find the time to sand it down to size. You’ll have to use your imagination. I am about to get a new propane tank and start on a new tanto, this one with proper tapering and better claying. I will post it when finished in a new post.

So, you want to forge knives… Well, I just started myself, only made a few blades so far. I have learned some information useful to beginners that might not be readily available online, or scattered all over the place. These lessons learned might save you some time, aggravation, even a few dollars.. Follow any advise here at your own risk, I am no expert and forging is inherently dangerous.

About forging: Forging is not just that, hammering a red-hot piece of steel into a blade. You need to consider what else comes into building a knife. A lot of time will be spent grinding, sharpening, and polishing. If using sand paper gives you unpleasant goosebumps, or you cringe at the thought of getting burned or cut, you might want to look into knitting. Heat treating is not as simple as plunging your steel in water. Some knowledge of metallurgy about different steels and what happens to them at different temperatures is a must. Annealing, normalizing, hardening and tempering are important phases in creating a blade. Then you need to make a handle, sheath, and sometimes apply different finishes. Building a knife is a whole process, forging is only part of it.

Forge: I started by building a charcoal forge. It worked, but it is slow and dirty, a pain in the ass, really. Sure, It only cost me $60, and I could have built a better one. Gas however is fast and clean. I bought a $200 forge on Ebay and never looked back. The next one will have a round shape though, and be covered with refractory cement instead of KAOWool. A round forge body creates vortexes resulting in a more even temperature and probably gas saving. With a hard refractory coating, you will never breathe dangerous ceramic fibers.. Coal is another good option, also dirty, but better in my opinion than charcoal. See my gas forge here.

Steels: Many beginners will try to find some scrap steel at the junkyard. You might get lucky finding what you want, but you might not. Spending hours hammering steel to find out that it won’t harden is no fun. I just ordered six 3/16 x 1” x 60” bars of 1080 from Admiral Steel for about $90 (with shipping)! That is enough to make from 30 to 40 large knives. Less than $3 per knife. Mystery steel is like mystery meat, you really don’t know what’s in it and most of the time, it doesn’t turn out to be that good. 1075-1080 is probably the best steel to start with. It is a simple steel, easy to heat treat and forge. You can temper it in a kitchen oven at 450F. Tool steels and other higher carbon steels require better temperature control and higher tempering temperatures, around 550-600F. It isn’t worth my time fishing for scrap in a junkyard. I would probably often have to discard half-finished blades, so the savings are really not significant enough. Buy good steel, pick one kind, learn it well, you’ll get consistent results allowing you to refine your process. More on steel selection.

Heat Treatment Anneal every time you stop working for the day. Normalize three times before hardening. Use a magnet to determine when the steel has turned to austenite and is non-magnetic. Go slightly higher, and let the blade soak for ten minutes at that temperature. If you forge or heat-treat too hot, your steel will decarbonize. Quench in warm oil (140 to 160F). Cold oil will actually not cool your blade as fast. Avoid motor oil, it’s too thick. Thin oil, such as ATF or thin mineral oil is better. Don’t move the blade sideways while it cools, but front and back. If you want to create a hamon by differential clay hardening, cover the back of the blade with a refractory like Satanite (1/8” thick layer). Temper immediately after hardening, three times one hour at 450F. If you use a different steel than 1060-1075-1080, find out what the numbers are, don’t just guess..

Anvil: I bought a cast iron anvil at Harbor Freight. It is way too soft! Here is when a trip to the junkyard might save you money. A 100Lbs hardened steel anvil will cost you $400 to $600. Find any piece of steel with a flat surface, as heavy as you can carry. Secure it to a solid base, so that you can forge standing up. Thanks to my friend Phil and his father at Seaboard Steel, I was able get a heavy piece of steel which originally was a jaw that grabs giant steel plates. It must be heat-treated because it is very hard. We welded it to an I-beam and a half-inch steel base.

Click on the image to enlarge..

Hammer and tongs: Almost any hammer will do (you might want to put a nice smooth finish on it’s face), but you need tongs to grab your blades. I started with a pair of wise-grips, but they are too short and awkward to use. Having a piece of red-hot steel fly out when you hit it is pretty scary. Don’t ask me how I know.. (well, I still have one scar on my ankle..) Start by forging tongues. It is easier than forging a blade, and you will need them anyway.

Click on the image to enlarge..

Not the best looking ones, but they work just fine..

Safety: Wear heavy leather gloves and clear eye protection (clear to see steel color). I have a welding jacket with leather sleeves that’s perfect for forging. Make sure nothing close to the forge can catch on fire. That includes your propane hose in particular! Wear a respirator when grinding or changing your ceramic fiber forge insulation. Don’t forget, you’re building knives, they can get really sharp! Blades can fly off your hands while grinding, specially when using buffing wheels. You must be conscious of safety all the time. You don’t want to end-up in the hospital or dead because of a hobby!

Information: It is easier to start with some help. Browse the following forums online:

Document you progress. You might discover that a blade you forged displays great characteristics after some use, and not remember how you made it..

I highly recommend Wayne Godard’s $50 Knife Shop book:


Wayne Goddard’s $50 Knife Shop, Revised
And Tim Lively’s DVD:


Knifemaking Unplugged

I will add to this article once in a while as I discover new tips or pitfalls to avoid. Anyone with more experience than myself, that’s almost anybody able to forge a decent knife at this time, please add any advise for beginners you may have in the comments section below. Many thanks to the members of bladeforums.com for their feedback on this article!

After weeks of consideration and research on the web, I finally decided to buy a katana. Not a cheap wall-hanger, but a practical sword, forged by hand and differentially hardened. I am very familiar with knives, even started to forge my own. Swords however are mostly unknown to me. Why would a grown man buy a sword you may ask, well, I have a few reasons, and they have nothing to do with the “cool” factor. Swords are not toys, but deadly weapons. I place them in the same category as handguns and rifles. I came to believe that they are one of the best home defense weapons available. My interest in knives came from the staggering number of designs found for such a simple, primary tool. Metallurgy, the forging and hardening processes have always fascinated me. I have barely scratched the surface of that art, but I can certainly appreciate the skills it takes to forge a blade longer than a few inches, then harden and temper it properly. My life-long interest and practice of the martial arts also influenced my decision. I have long ago found out that most Asian disciplines only work in their context. Russian Systema however works in any circumstances and can make use of any weapon. Give me a frying pan and I’ll be immediately efficient with it using Systema principles. A sword, though presenting some challenges, shouldn’t be too much trouble. Of course, I will use a dull one or bokken for practice. Other sword designs were interesting, but the Japanese katana in my opinion is the best sword. It is light, razor sharp, and simple in design. Nobody wears armor these days, so a heavier sword would make little sense. The way these swords are made is also fascinating. Even if you have no interest in swords, you can’t but admire the dedication and skills of Japanese sword-smiths in their pursuit of perfection. I never get tired of watching the following documentary from National Geographic:

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I can’t pay three highly skilled artisans for three months to forge me a blade, so I have to accept some technological shortcuts. Modern steels like 9260 Silicon Alloy Carbon Spring Steel are even better than traditional tamahagane. It’s not traditional of course, but much cheaper. The folding process becomes superfluous, since the carbon content of modern steel is constant throughout the material. I would love a folded blade, but the cheapest ones, forged in China, start at around $1000. More than I am willing to spend for a first purchase. A San-Mai construction like my Cold Steel Master Tanto would be desirable too, but simply too expensive. There is one feature I really want however, and that is a differentially, clay-hardened blade. This process of covering the back of the blade with thick clay before quenching in water produces a very hard edge and a soft back (watch video above). This way, a sword will bend but not break, while still holding a razor-sharp edge. It also produces a visible line of hardness called the hamon. Most replicas have a fake one, acid-etched on the blade. I can’t accept “fake” anything, so my choice becomes fairly limited for an affordable real sword. Thanks to companies like CAS Hanwei and Cheness Inc., real forged blades from China are available, starting at around $160 for something that won’t come apart in your hands and take a lot of abuse before breaking. Shell-out $200 to $300 and you get a serious tool. My choice is the Kaze Ko-Katana. With a 21-inch blade, this katana is about seven inches shorter than a regular sword. These swords are also called chisa katanas, and are easier to use in tight places. Here is another review of the Kaze (watch the cutting test video). I got a 10% discount and ordered mine for less than $200, with free shipping.

Proceed to the full review

The charcoal forge was fun to build and use, but let’s face it, it takes forever to heat-up and it is pretty dirty. If I made another one, it would be more of a closed design to concentrate and conserve heat, and would have a good hand-cranked blower. So, I went on Ebay and shopped around to finally order a two-burner gas forge from CKForge for $199 plus $45 shipping. The design is basically a steel box opened on both ends and lined with insulation, with a firebrick on the bottom. A two-burner assembly is screwed on top. Connect a propane tank (I borrowed my housemate’s grill tank), and you’re ready to go. I wish the holes for the screws had been pre-drilled. Of course it is reasonable for the seller to assume that someone ordering a forge would own some kind of drill! My cheapo Chinese drill press from Harbor Freight did the job nicely. The forge is well built, with decent welds, no trouble at all, and it worked flawlessly right out of the box, but for the drilling.


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Starting the forge was a walk in the park compared to my charcoal model. I grabbed the torch I use for Crème brûlée, lighted it, turned on the tank valve, then the regulator, barely, and finally the forge valve while sticking the flame inside the forge; it worked instantly. After what seemed a very short time, I had a red hot railroad spike on my anvil. A couple hours later I was finished shaping the blade! Not bad for a first timer, I thought, and so much faster than my charcoal home-made forge..
Forged Railroad Spike Knife

Forged Railroad Spike Knife


It looks a bit like a butter knife at this stage, but a little grinding will make the blade look a tad more “aggressive.” I traced a bevel line with a black marker, and a line where I will remove a bit of metal at the tip so that it isn’t so round. You can’t see it on the photo, but the edge is pretty close to it’s final shape, about 1/16th, 1/4” at the spine. The pommel looks a bit weird, but I didn’t know what else to do. A couple holes there for a lanyard will be nice. I flattened the ends so that it could be used like a hammer. At the end of my session, I brought the blade (now I can call it that!) to cherry-red hot and switched the gas off, leaving the knife to anneal (air-cool slowly to release stress) in the forge.
[warning]That small table you see under the forge on the video caught on fire after about an hour. So, if you get a similar gas forge, make sure nothing around it can ignite! Fortunately I had the garden hose handy.. And make sure the gas hose doesn’t touch the forge or dangle close to the openings. Now, that would be trouble![/warning]

June 24: Since I have to wait to get a decent grinder, I figured, what the hell, I’ll just make another one.. This time I am trying a double-edge knife with a twist in the handle. My friend Erin surprised me by setting up my anvil on a log, putting sheets of refractory material under the forge and installing a light above the whole setup. So, he’s drinking my beers right now and I am pretty happy with the installation. Here is a new video of me starting on the new blade:

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And below, number two:
Second knife, double-edge with a twist

Second knife, double-edge with a twist


Next steps: Grinding, heat treatment, and sharpening. I might wrap the handle with fiberglass tape and epoxy, or opt for something more traditional. I am also thinking about parkerizing the handle and maybe part of the blade, but a nice polish would probably look better..

I finally decided to go ahead and build a charcoal forge to make knives out of railroad spikes, motorcycle chains, suspension springs and other junk steel. I have never done this before, but as always, I researched the subject thoroughly before diving in. My goal is to produce crude knives at first, without using any electricity. Using a grinder is thus not an option and the shape of the blade will have to be hammered as closely as possible to it’s final size. Forging a knife is one of those basic skills I think I ought to learn. Not that I expect to ever do it out of necessity. I want to experience the satisfaction of building the most basic tool with my own hands..

My first step was to find an expert on the web, and that turned out to be Tim Lively. His washtub forge seemed to fit my bill pretty well. Problem is, Home Depot didn’t have the washtub, so I settled on a large terra-cotta bowl. I hope that lining it with adobe (50/50 earthen clay and sand) like the washtub forge will prevent it from cracking.

To be able to reach forging and welding temperatures, you need to supply the burning charcoal with fresh air. I bought a bunch of pipes and fittings for that purpose:

Steel pipes assembly for forge air supply.

Steel pipes assembly for forge air supply.

I used a cheap drill press from Harbor Freight to drill 1/4 inch holes in the pipe that lays at the bottom of the bowl:

Drilling 1/4'' air holes in the top pipe assembly.

Drilling 1/4'' air holes in the top pipe assembly.

The assembled result looks pretty good:

Terra-cotta bowl and pipes assembly.

Terra-cotta bowl and pipes assembly.

Using galvanized pipes isn’t the brightest idea since they release toxic gases when heated. I’ll have to work upwind to avoid poisoning myself! I suggest anyone building a forge to use something else! Forge blowers on Ebay go for about $150 to $250; more than I care to spend for an old rusted piece of cast iron. I am not sure yet what I’ll use as an air supply. Any suggestions?

Now that I have the hardware, and while the adobe dries, I need to learn how to actually forge a blade. Fortunately, Tim Lively has an excellent DVD on the subject:

Mixing the sand and clay took forever. I had to use my Khukuri to chop fist-size blocks of clay, wet them and take little flakes out until the whole thing was gone. You have to be carefull not to add too much water. I tried to obtain the consistency of peanut butter. I started packing it under the pipe. Hopefully I didn’t leave any air bubbles in the adobe. Now the mix needs to dry for a few days.. I can see little cracks already, but it’s a forge I am making, not a teapot, so it doesn’t really matter, I’ll patch them up later. I also want to raise the sides a bit so that the charcoal stays in the middle, over the air holes.

Adobe drying in the bowl, aroud the pipe with air holes.

Adobe drying in the bowl, aroud the pipe with air holes.


Part two promises to be more interesting. The adobe will be dry and I will actually fire the forge up and try to hammer a railroad spike into a useable blade. I will film my efforts and post the video. Continue to Part 2.