The following article by Albert W. Fischer originally appeared in the August 1996, issue of our Bulletin.
Al Fischer was an engineer for General Motors where he worked directly with another ingenious engineer: none other than Charles Kettering. Al's retired now and lives in La Jolla, California. He's been an amateur violin maker since 1939.
Al has been a SCAVM member since January of 1968. He was president of the Association during 1970. He is a regular contributor to our Bulletin and is the designer of numerous ingenious jigs and fixtures useful in instrument making. He is well known for the application of power tools to the art, but is very adept in the application of hand tools as well.
Your editor, Leonard Showalter, wasnt able to attend the August meeting of SCAVM. He asked me to write the highlights of the meeting for the benefit of the members who were unable to attend. The meeting consisted of a presentation on how to easily make variously shaped palm gouges that are ideal for carving the scroll and also useful in other areas of the violin. A display of twelve various palm gouges in its own convenient hinged box (see illustration) was available for the members to examine.
When I carved my first scroll some years ago, I found it was more convenient to carve the helix on the scroll by holding the neck in my left hand and carving with a gouge held in my right hand. The gouges I had at that time were beautiful conventional gouges made of polished English Sheffield steel about 7½ inches long. To control the accuracy of the cut, I found I was holding the blade with my fingers close to the cutting edge and my palm barely touched the handle. This allowed me to easily rotate the scroll and always have the cutting operation on top where it is easily seen, but the pushing had to be done with the fingers which, after a while, tired from holding the blade. I thought this method of carving was unconventional until I witnessedon Public TVa woodcarver from Oberammergau hand carving a small wood statue. He was holding the statue in his left hand and carving the detail with a long gouge held in his right hand. You guessed it. He held the blade with his fingers close to the cutting edge. The thought then occurred to me: why not make short gouges where the handle will fit in the palm of ones hand and be more comfortable to use?
I guess there were palm gouges available at the time for the model maker, but they were hand forged from solid carbon steel and expensive if one were buying a dozen different shapes. Some of the sizes I wanted were not even available. I had some old dull hacksaw blades in a drawer for some reason, and maybe this was the reason. I felt they would make good palm gouges, and they did.
The gouges I made are shown in Fig. 1. The simple forming tools used are shown in Fig. 2. The metallurgy of working high carbon steel is shown on the chart in Fig 3. The chart shown at the meeting was in color and I regret we cannot show it in color here.
To begin, the blade is made of high carbon steel having 1% or more carbon. Hacksaw blades and clockspring meet this requirement. Some hacksaw blades are made of high speed steel or alloyed in other ways, so avoid these. The heat treatment is more complicated and I feel the cutting edge is not as good for wood as high carbon steel. If the sparks are few, and a dull red in color, the material is not high carbon steel, so do not attempt to use it. A good alternate material for making the gouges is blued clockspring. San Diego Hardware has a good selection of coils of various widths and thicknesses and they will cut off any length you want. I like it because of the choice of sizes and the edges are already nicely rounded. No teeth to file off. Whether you use hacksaw blades or clockspring, the material will have to be annealed to soften the metal for forming the blades without cracking. This can be done with an ordinary propane torch by slowly heating it all over to a dull red color. Annealing does not happen in an instant. The longer you heat it to a red color the better. Think of it as an ice cube melting in a pan of water. It doesnt melt instantly, and so it is with high carbon steel when changing from martensite carbon (hard) to pearlite carbon (soft). See Fig. 3. The flat part of the curve shows the time element required for the change to occur. I found it easier to anneal the strips if precut to 3-inch lengths. Mark the strip with a carbide scribe where you want the cut to be made and just anneal those areas. You can now cut that point with tin snips. Hold the 3-inch strip at one end with an old needle nose pliers or a pair of tongs and slowly heat to a dull red all over. Reverse ends to be sure to anneal the end held by the pliers. Place against something noninflammable and allow to cool in air to room temperature. Do not quench or cool in water.
Fig. 2 shows the simple tools used to form the blade. Most hardware stores have HANDI-METAL in various sizesone being ½" square by 12 inches long. Cut this bar in half lengthwise and clamp the two halves together so a series of holes from 3/16" dia. to 7/16" dia. can be drilled in the drill press. The holes should be drilled exactly on the split line, so use the method shown in Fig. 2 to insure accuracy. After drilling, realign the two halves as shown and bolt or rivet together. Clamp some suitable pins in place for alignment when drilling the rivet holes so you will have a continuous groove without a step. Since the gouge stock is approximately 1/32" thick, you will need forming pins about 4 inches long and 1/16" smaller in diameter than the diameter of the grooves. These can be long nails, bolts, rods, or whatever is available in your shop. I keep an assortment of drill rod handy and it is ideal for this purpose. It is a good idea to grind a small flat where you will strike the rod with a hammer to avoid getting hammer marks all around the rod. To do the forming you will need a heavy hammer such as a machinists hammer and some heavy metal object to pound on. A heavy machinists vise will also do. I use a small anvil made from a 12-inch section of railroad track.
Start the forming of the blade by placing one of the annealed blades across the 7/16" dia. slot with a 3/8" dia. rod on top. Give the pin a smart blow with the heavy hammer and continue with the next inch until the entire length is partially formed. Repeat this operation until the entire length has a uniform 3/16-inch radius inside.
At this stage a decision must be made as to the radius desired on the cutting edge of the blade. If it is a 3/16-inch radius, leave the blade as is and continue forming the 1-inch long tang. Reduce the tang radius first with a 5/16" dia. pin in the 3/8" groove and then with a ¼" dia. pin in the 5/16" groove. Continue shaping the tang radius until it slips easily in the 5/16" dia hole in the handle. For a smaller gouge radius use smaller grooves and smaller pins until you have the desired radius. For larger radius gouges open up the blade for about an inch by shaping over a larger dia. piece of steel or a pipe using a plastic or lead hammer. Never hammer on the blade itself with a steel hammer, as it will leave hammer marks in the soft metal that are a nuisance to polish out later. At this point, check the blade for a twist or straightness. Since the metal is still soft it can easily be straightened with a pair of pliers.
I am sure by this time you will be an expert at forming a gouge blade from perfectly flat to as small as a 1/16" radius. The blade itself need only be about an inch long and the rest can taper into the tang. For smaller gouges you may have to use narrower stock or else file the sides away if they become too high. Other shapes will come to mind for carving difficult areas of the scroll. While the blade is still in the annealed statebefore hardeningshape the cutting edge exactly as you want it on the finished gouge, by filing or grinding, and then honing away the feather edge until it looks like a finished gouge. I recommend this because the metal is so thin it is almost impossible to grind it after hardening without overheating and destroying the hardness of the cutting edge. Any shaping after hardening must be done on a slow wet wheel or by honing on a coarse oil stone.
Now comes the important critical partthe rehardening of the cutting edge. This can be done by holding the tang with a needle nose pliers and heating with a propane torch. It is not necessary to harden the whole bladein fact it is better to leave the tang annealed and just harden the last half inch of the blade. Direct the flame about one half inch from the cutting edge and watch the color change. It will change from a yellow to a brown, then blue, and finally a dull red. At a cherry red color it will seem to stabilize and not change any further. This is normal. See the chart, Fig 3. Remember the ice cube analogy. You are changing the soft pearlite carbon to the hard martensite carbon. Continue heating until you detect a change in color to an orange red color, at which point quickly quench in a container of water. A word of cautionkeep the flame away from the cutting edge and let the color creep to the edge rather than applying the flame to the edge directly; otherwise the thin edge may be burned and made useless. The biggest mistake one can make in hardening high carbon steel is to be impatient and quench the steel before it has all changed to martensite carbon, so watch for the orange-red color. In this state the cutting edge is glass hard and very brittle and could easily chip if used, so another operation is required called tempering.
Tempering softens the hardness of the metal for the use intended. Where the material is bent, as in a flat spring, or hammered on, as in a cold chisel, the tempering temperature may vary from 400° F to 550° F. Since the palm chisels are intended strictly for shaving woodno pryingI prefer to keep the cutting edge fairly hard and temper to a temperature of about 400° F. Here again we are making use of the color of the base metal and, since the hardening of the blade left a black oxidized surface, it is necessary to first polish the blade to the base metal. You will want to do this anyway for appearances if you take pride in your work. I clamp the tang in the vise and sand with strips of aluminum oxide or emery clothnot paper. If you have a buffing wheel you can bring them to a nice polish as you would your golf clubs. Tempering can be done in good light with a propane torch, but it is risky because the temperature changes so quickly. Use a smaller flame and hold it some distance away from the blade. Here again point the flame toward the center of the bladenot the cutting edge. Watch for the first sign of a pale yellow color and let it slowly creep to the cutting edge. Immediately remove the flame and allow to cool in air. A far safer and easier method is to use the kitchen oven, preheated to 400° F. Try a test piece to make sure you get a faint yellow color and remove and allow to cool in air. With the oven method you can temper all your blades at one time.
You may have your own idea for a handle, but I found the handle shown in Fig. 1 comfortable to use and very easy to make. The simplest way is to use ordinary 1" dia. hardwood dowels cut in 2½" lengths. They are readily available in maple, black walnut or other woods, or, if you have a wood lathe, you can turn your own. I turned my handles out of cocobolo which I had available. Drill a 5/16" dia. hole in the center of one end, one inch deep, for the tang of the blade. If a 5/16" pin is fitted tightly in the hole, the handle can easily be shaped in the drill press using an improvised wood steady rest and an old file ground for a scraping edge on the end. If you have a wood turning lathe, I do not have to tell you how to turn a nice handle. The gouge is assembled by coating the tang and the hole with epoxy cement, inserting the tang and then inserting a one-inch length of ¼" dia wooden dowel to fill up the hole. Add additional epoxy cement until it is flush with the top.
The final sharpening is done by honing only, and finally stropping on a leather-faced wheel. See the reprint of my article in the May, 1966, Bulletin. Never attempt to grind the edge on your electric grinder. The metal is so thin that you will soon burn the edge and render the gouge useless. A slow rotating wet wheel is permissible, but usually a coarse hone will remove any nicks or reshape the wheel.
With a nice set of gouges it is wise to make some sort of block for mounting them on the bench, or, better yet, a nice hinged box such as that at the beginning of the article, rather than let them rattle around in a drawer.
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