Making your own furniture is a sign that you’re a practical craftsman. How about taking it a step further by making your own tools for making your furniture? The process for making chisels and gouges isn’t as intimidating as it might seem. Two propane torches will do anything a coal forge can do, so you won’t need expensive special equipment.
To begin with, let’s talk about steel. The important ingredient in steel is carbon. More carbon in the steel means a longer edge life and a better ability to accept heat treatment. Low-carbon steel is used for any item that does not need to have a durable edge.
High-carbon steel is catagorized by the percentage of carbon ranging from 50% (1/2 of 1 %) to 1.25%. The ideal steel for fine woodworking tools is around .75% to .95%. Commercially available W-l tool steel (drill rod @ .95% carbon) is excellent for this purpose. I buy my steel from Pacific Machinery and Tool Steel (see «For More Information» on page 40). They can supply many sizes of flat and square stock of W-l through the mail.
For most chisels you’ll want material that is 1/8″ to 1/4″ thick. The width, of course, depends on the size of tool you want. Firmer chisels for rough work should be fairly stout, while paring chisels don’t need much thickness. Square stock is ideal for mortise chisels.
An excellent alternative to buying new tool steel would be to use an old leaf spring from an automobile. This is what I used in the demonstration photos. When it comes to using leaf springs for this type of project, older is better—with pre-World War II leaf springs being the best. This is because alloys were developed and added after WWII that makes it somewhat more difficult to harden and temper the steel.
Heat Treating When steel is worked, it gets a certain amount of uneven tension in it. This creates stresses and may cause the billet to crack. To get this tension out of the steel, it needs to be relaxed or annealed. Annealing is done by heating the billet to its critical temperature of 1450° Fahrenheit and then allowing it to cool slowly in a bucket of wood ashes or air-slaked lime. This brings the steel to its softest state so it can be worked without harm.
After working the steel, it is necessary to harden it. The billet is heated to 1450° and then cooled quickly by quenching it in 10-weight oil (vegetable oil will also work). The way to tell that you have reached the critical temperature is to touch a cow magnet to the steel as it approaches a cherry red heat. At exactly the point that the steel reaches 1450°, the magnet will no longer be attracted to it.
After hardening, the tool will be full of tension, so it needs to be tempered back from its total hardness to the proper hardness desired for the use of the tool.
Whether you’re using leaf springs or new steel from a jobber, it will be in an annealed condition—soft and ready to grind. Cut your billet from the leaf spring with a torch, or better yet. a cut-off wheel. If you use a torch, leave an extra 1/4″ to 3/8″ all around and then grind it back. Be sure to read all information pertaining to the speed of your grinding wheel, as well as any books dealing with grinding in general, so that you’re well-versed in safe grinding practices. I ground the nail off my index finger in a split second because I was careless. Be sure to hold the workpiece with a pair of pliers, wear safety goggles, and watch out for long hair and loose clothing. I even wear ear plugs and a face mask.
Be sure to quench the tool frequently as you grind to prevent accidentally drawing the colors, as when a piece of steel turns blue from getting too hot. If the steel does turn blue while grinding, you should anneal it. and start again.
I use a double-reinforced snag wheel to remove a lot of material quickly. It’s rated at 16-grit and casters use it to clean rough-cast items. However, any grinding wheel will do.
For a tool that will be struck, shape the billet with a 3″ or 4″ long blade and a 2″ to 3″ tang. Hand-held detailing tools can be an inch or so shorter. Use a file to finish up the area where the tang meets the body of the tool.
To make a gouge, slice a lengthwise section of pipe that is the appropriate diameter and clamp it in a vise. Heat your billet to no more than a light yellow heat and use a ball peen hammer to shape it down into the concave section of pipe. Don’t get the steel too hot, because if it sparks at a white heat, it’s ruined.
After shaping the tool, grind a bevel that suits the purpose of the tool and the kind of wood you will use it on. I start at the grinding wheel, then progress to a drum sander. and I finish up on a buffing wheel. I slice some “Polish-O-Ray” buffing compound off the tube, melt it in a double boiler, then paint it evenly onto the buffing wheel and let it dry overnight. This aggressive buffing compound takes out the scratches put in by the sander. Carefully refine the edge until there is no light reflected off it. If you raise a burr on the back of the tool, remove it by stropping it on your jeans.
Once the edge is created, go ahead and harden the tool. It is not necessary to anneal after grinding if you have not “blued» the edge. Set up two opposing torches (I use model #JT99 from the Bemzomatic Company) and heat just the last two inches of the steel gradually and evenly, allowing the heat to seep into the bevel from other portions of the steel. When it reaches the critical temperature, quench it by lowering it vertically straight into the oil so it cools evenly.
Be careful not to drop the tool when it is hardened; it will probably break. As mentioned above, the tool needs to be tempered back from its total hardness so it can be honed more easily and so it will be less brittle under the stress of use.
The proper temper is determined by observing the oxidation colors as you reheat the tool. After hardening, there will be a grey-black color on the surface of the tool; polish this off with emery cloth or the buffing wheel.
Run the flame across the width of the blade at its base (just above the tang). The oxidation colors (pale yellow, darkening to a gold, into a purple, into a blue) will run up the body of the tool to the edge. The color that winds up at the edge when you remove the heat reflects the hardness. Pale or straw yellow is very hard and brittle, good for tools with odd shapes that won’t be struck. Purple is the ideal color for chisels and gouges.
When the colors become apparent and start to move, remove the flame until the colors stop moving. Then add a little more heat to move the colors slowly up the tool. When the color you want reaches the edge, remove the flame. It doesn’t matter how fast the steel cools at this point, so you can let it air cool or quench it in oil.
Slip a washer over the tang and apply your homemade handle to the tool. Hone it on your bench stones. and then start chopping.