MAKING A WOODTURNING CHISEL
Many excellent chisels are available from many sources if you are willing to pay premium prices for them. With a little practice, you will be able to fabricate completely from scratch, a fine chisel you will be proud to show off to your friends. Woodturning chisels come in two basic species, gouges and flat, straight or skewed types. The gouges are always round in cross section and the flats can be made from either square or rectangular stock. We will start with a flat square short skew. Choose a length of 3/16" square tool steel and slowly grind an angled double facet on one end of it. The skew angle should be around 45o while the bevel angle should be less steep. An easy way of figuring the bevel angle is to grind it about as wide as the thickness of the stock. Be sure to dip the tool steel frequently in water during the grinding process to prevent burning the steel. After grinding the basic bevel you should hone it on a fine oil stone to create a fine secondary polished bevel and remove the so called wire edge that is produced during grinding. All that is left is to heat treat the edge of the tool as we did with the prick punch. Put the heat treated skew aside and so can begin to make our first gouge. The body of the gouge is made from drill rod and starts with it chucked or held in a collet and not protruding too far out. After facing the end, it is center drilled and drilled on the end to create a hole about 1" deep. Use a drill one half the diameter of the chosen drill rod. Use plenty of cutting oil and a slow speed and feed to minimize any wandering of the bit. The drilled end needs to have about one half of its diameter ground to expose the flute. This can be done on a regular bench grinder as not many of us own or have access to a surface grinder. Grind the end back to about the depth of the hole and begin to shape the cutting edge. This is where the choices become numerous. The edge may be ground with a steep or shallow facet that runs square along the edge or shaped like a thumb nail. The thumb nail shape is very popular among spindle turners. If you are really interested in woodturning chisels, the different types, uses and learning the art of grinding chisel edges, I recommend that you acquire some books or videos on the subject as it is a very extensive one. Our present discussion will concentrate on building a basic tool. Once the tool steel has been drilled, ground and shaped, it will need heat treatment and polishing before the handle is made. This is the area where most commercial chisels fall flat on their face. We will make a custom hardwood handle for our chisel with a threaded solid brass ferrule. The ferrule is the metal ring that wraps around the handle where the tool shaft joins it. It is supposed to secure and prevent the tool from levering and splitting the wood during strenuous work. They seem tight when they are new but after the wood shrinks a bit, they soon become loose and tend to fall out. For my handles I like to use a very dense, oily type of wood such as some of the rosewoods. Some domestic fruit-woods like cherry, apple, or pear will also make very good handles. The so called ferrule is a plumber's compression nut available at any home center. Some have a center hole but I prefer the cap nuts without a hole so I can drill it myself to match the diameter of the tool steel. Chuck the stock for the handle and center drill it to accept the live center and turn it round. The tenon will need to be turned to a diameter that will begin to accept the nut. It has to be tight enough to require the use of a wrench to screw the cap nut on the tenon. The depth on the tenon has to be less than that of the cap nut so it will sit tight against the shoulder created behind the tenon. Screw the nut all the way against the tenon shoulder and support it again with the live center. Proceed to machine the corners off the nut until it is round and finish it by polishing it with 320-600 grit paper. Chamfer the edges of the ferrule and begin to hand turn the handle to a pleasing, comfortable shape. Do not part it off as the hole for the tool steel still needs to be drilled through the end with the ferrule. Drill the hole to a 2" depth with a bit matching the tool diameter, support it again with the live center, finish sand the handle and part it off making a rounded end on the end. Place the tool steel, with the cutting edge down, gripping by the sides in a vice and drive the handle into it as far as it will go with the help of a rubber mallet. Chuck the chisel by the by the ferrule so you can part off the waste wood and apply a friction polish to it with a clean rag at high speeds until you feel it getting hot. Friction polish is made out of equal parts of shellac / boiled linseed oil / methanol. Keep this mixture in a small squeeze bottle with a snap top and shake well before each use. This system of polish goes back a long way, deriving its origins from the old, time consuming French polishes. Because it is applied at a high speed, it dries extremely fast. The chisel is now finished and ready to use and show off. The finish can be renewed by applying more friction polish.