Forged Bowl Carvers Adze

Up until quite recently the bulk of my carving experience has been either extremely small scale or smooth surfaced basic shapes such as spoons, bowls, and the occasional magic wand. As it tends to happen I decided for no rational reason whatsoever that I wanted to carve things that were as detailed as my smaller work, but on a larger scale.

The first step in any new obsession is gathering intel. I researched Japanese Noh masks, antique signage, and creepy puppets. I filled a Pinterest board with things I wanted to carve. Hours were spent pouring through Google images. Ideas were forged, techniques analyzed. Plans emerged.

I needed tools. Something larger than the micro chisels I forged for carving Nestuke (previous obsession, groovy stuff, google it). This is why I initially made the mini-forge. Firing up the full sized charcoal burner was both expensive and a complete pain. I had basic carving knives, but the type of work coming next called for all kinds of fan tail chisels, spoon gouges, and adzes. Goody.


The first tool that grabbed my fancy was a miniature adze found on knivesbynick.co.uk. I fancied it for several reasons. It was designed with interchangeable blades, the blades could be made from flat stock, and it was fairly primitive. I like to keep things simple.

As simple as making stuff from scratch can be.

Luckily, there just happens to be a large number of L6 flat stock pieces on hand. I have been hoarding sawzall blades for just such an occasion.

This one should do nicely.

 Cut to size with an angle grinder.

And the bit that has a date with the flame.

One piece of advice, if you aren't familiar with the metal you are going to use you may want to take a minute to figure some things out. With saw blades you have to consider what it was used for. Reciprocating saw blades are designed to be heat hardy, their strength can't rely too heavily on the heat treat alone, so none of them are composed of simple carbon steel. The other metals in the alloy can make you project piece react in interesting and unpredictable ways when forged and heat treated. 

Some blades are bi-metal. This means that two metals were chosen for different properties, then married together in some configuration. Usually the cutting edge is a harder, more brittle metal. The body and the bulk of the blade is made out of a tougher or springier alloy. These blades are useless for making a cutting tool. The teeth are the only bit that can hold an edge when hardened, and the alloys are usually to complex to be effectively hardened in the home forge. 

If the blade you choose has no markings left to indicate that it is bi-metal you can lay the blade flat and take some 120 grit sand paper to it. Rough polish a small section of the side taking care to expose both the side of the blade body and a few teeth. Dunk the blade in vinegar for a few minutes to etch the metal. Different alloys react in different ways to the acid in the vinegar. If it is a bi-metal blade you will see a clear line where the two metals have been welded together just above the cutting surface. Sometimes the vinegar is overkill, just a quick polishing will reveal the line.

Once I know the piece is homogeneous I usually do a hardening/file test. Cut off a smallish piece of the blade from a place destined for scrap. Heat it to critical temp, the point at which a magnet no longer attracts the metal, about bright orange. Let it cool slowly. Sticking it in sand or laying it on the edge of the forge slows the cooling process. This is called annealing. It takes the metal from a hardened and heat treated state back to its natural state. A file should readily cut into the edge after the metal has cooled. 

Heat it back to critical, then plunge it into oil. This is hardening. I mentioned this briefly last time, but I'll go into slightly more detail here without attempting to fully explain the dark and terrible forces involved. It is important to have a basic understanding of what is going on. When the metal is brought to critical the molecular harmony in the steel responsible for its magnetic properties is thrown into chaos. As the atoms spin around the micro magnetic poles are thrown out of alignment making the mass nonmagnetic on a micro scale. Once brought into this relatively free state the carbon in the steel begins to spontaneously form the crystalline structures responsible for the steel's final hardness. When the piece is flash cooled in the oil, the crystals are literally frozen in that structure. Once hardened, take the file back to the steel. If it skates across the edge without cutting in, congratulations, you have a hadenable piece of stock near its hardest possible state. If you were to hit with a hammer at this point, without tempering, the crystals would likely shatter and the metal would fail. More on that in a bit. 

This is an incredibly simple bit of forging once you are pleased with your metal. There are really only two concerns with this project. If you hammer on the metal after it is too cool you can crack it. If you heat it too much past past bright orange you'll burn the steel. Burning the steel just means it has become so hot that it begins to melt. The carbon in the steel is boiled to the surface and lost. Take the carbon content down too far, and it won't hold an edge. L6 is a pretty forgiving metal for both of these concerns. Just watch the temp, don't work the metal higher than bright orange or lower than a cherry red.

The image above shows the heat progression from the bright orange toward the tip, and the cherry red toward the tail. My anvil for this piece is just a rail spike stake that I ground into a small horn shape and set into an oak 4x4. It could just as easily be set directly into a stump, or held in a vice.

Working the piece is the exciting part when you are doing it, but the boring part in explanation. Suffice to say that I hit it with a hammer until it was at the correct radius. Any hammer will work for this thin stock, so use what you have available.

There is a choice to make at this point. You can shape the cutting edge, while the steel is relatively soft, using files and stones. This is easier than shaping after the steel is at finished hardness, but the thinner the edge, the more likely it is to burn off during the hardening process. I choose to heat treat prior to shaping because I have a belt sander that will do the majority of the work on a hardened blade.

The finished piece is heated to critical and cooled in a pre-warmed mixture of recycled vegetable oil and used motor oil. No special reason, just what I had. There is science type stuff involved in choosing a quenching bath to match the steel, but L6 works good with oil. Water and salt water baths quench the steel faster, locking it in a harder state, but quench a really carbon heavy object too quickly and it will end bad. High carbon steel, like recycled file knives, will crack when cooled in water. L6 and most spring steel will quench super hard in water, but warps pretty badly without really knowing what you're doing. Oil is by far the safest route for a beginner.

When quenching a blade it is important to dip the blade in quickly, cutting edge first. Move it around while holding the piece suspended in the oil for thirty seconds or so. If you don't keep the blade moving small pockets of air will form next to the surface of the blade. The steel in contact with these pockets will cool at a different rate. The expansion and contraction forces inherent in heating and cooling steel can cause the finished product to twist and warp in undesirable ways. Let's keep that to a minimum, m'kay.

As I mentioned earlier, a hardened blade is pretty brittle. The answer to that problem is tempering. When you temper a blade, what you are doing is heating it to a certain temp and holding it there to soften the metal. The overall hardness goes down, but the toughness is increased. There are a ton of methods on how to do this, but for utter simplicity I'll stick to the basics for now. I use my electric oven for tempering. Even if you scrub the blade this results in some smoke and the odor of burning oil. You've been warned. I want this to be a reasonably soft blade for wood carving involving a leveraged prying force imparted by the handle. A super hard blade is too brittle for this tool, especially with a blade this thin. For those in the know, that is toward the blue end of the color tempering spectrum, or about 450* F for 30 to 45 minutes in my oven. Ovens vary, so some experimentation is needed. Polish the cutting edge of the blade, and put it in the oven on a cookie sheet, or on some foil. Start about 400 degrees for 30 minutes. If the polished area has already turned to a medium to dark blue turn off the oven and pull out your finished blade. If the polished area has turned a straw yellow to brown color without getting any darker you're on the right track. Turn up the heat 10*, leave the blade for 10 more minutes, and check the color again. Repeat until you get a lovely royal blue.

Once my blade was finished I carved up a quick handle, and drilled a hole slightly smaller than the blade. I used a flat chisel made from a straightened out spring to square the edges of the round hole to fit the blade. You could heat the tang/tail end of the blade prior to heat treating and burn out the corners of the square hole if you prefer. Up to you, your tools, and your supplies. I carved a quick tapered wedge from osage orange to hold the blade in place, and the rig was complete.

It is way too light for chopping strokes, but the leverage in an underhand push stroke is amazing. The amount of wood that can be removed in a single stroke speeds up reducing processes dramatically. It also affords the hand a lot of control in detailed carving and planing. It isn't as practical for spoon bowl carving as I had hoped, but that might have more to do with the angle of the blade, and the bevel of the cutting edge than anything else. Since this little guy was completed I have churned out a couple more blades to fit this handle, and the plan is to make a few handles with different angles to make a versatile carving system for my travel and bushcraft kit.

This thing has been a blast to carve with, and has inspired a few more tools that will be coming along shortly. I've been working on some finer detailed carvings, like these masks, that are creeping ever closer to completion. The demon mask, pictured here with the latest carving tools, is going to be a long term project. It keeps forcing me to make new tools that I didn't know I needed until I needed them. His write up is in the works, but still a long way off. Info on the tools, however, is just around the bend. I'm also compiling a bunch of realizations that have flowed out of my journey back into writing that have informed my process. Hopefully I will be able to share something on that front in the near future. In the mean time if I can offer any assistance, clarification, or just words of encouragement let me know. Until we meet again, go make something.