I've been reading Jay Light's excellent The Oboe Reed Book recently. While I found most of his book a real delight, I was disappointed - but not really surprised - at his cavalier dismissal of the single bevel reed knife. After describing the types of reed knives available, Mr. Light devotes a complete chapter to an explanation of how to sharpen one which is double hollow ground, saying, "If you insist on using a wedge knife, skip this chapter and get someone to show you how to sharpen it. "
I, too believe in going with what works for you, but too often people avoid the single bevel knife because they don't understand how to sharpen it properly. For me, a knife with a single bevel (a "wedge knife") works best. It has important advantages over blades. In this article, I will discuss why you might want such a knife, how to put it in shape initially, and how to maintain a sharp edge on it.
The edge of a single bevel knife is formed by the intersection of two surfaces: the back of the blade and the bevel. Woodworkers around the world use such edges in cutting tools such as planes and chisels, because they are strong and relatively easy to make really sharp.
The first advantage of the single bevel knife in reedmaking is that there is more thickness and mass immediately behind the edge than is found in most other knives. This mass stiffens the edge. Instead of catching and bending in the cane, resulting in chipped blades or "chattering", as thinner blades of other designs will, this stiffer edge takes off cane smoothly and uniformly.
The second advantage of the single bevel reed knife is that it is easier to sharpen, once it is properly set up. This is because you do not have to guess at the proper angle to hold the blade, nor must you somehow hold precisely that angle through the whole movement across the stone, stroke after stroke. Instead, all honing is done with a surface (either the bevel or the back) flat on the stone. The consistency of the sharpness of the edge from the edge from end to end and from sharpening to sharpening is, therefore, much higher. This can be particularly helpful to beginners, who may not recognize the difference between faulty knife technique and a dull knife.
The key to a really fine edge lies in three variables: the quality of the steel, the flatness of the two intersecting surfaces, and the smoothness of those surfaces.
For our purposes, the quality of the steel is mostly a function of its hardness and the fineness of its grain. Harder steel is supposed to provide both greater sharpness and more scraping between sharpenings. While I find I have to sharpen my hardest blades just as often as my others, I do think they take a sharper edge. Fine grain helps in edge retention. Those interested in how steel quality affects edge performance may wish to read Bill Shankus's article, Testing Wood Chisels," in the April/May, 1985 edition of Fine Woodworking (The Taunton Press, P. 0. Box 355, Newton, CT 06470).
Although the quality of steel varies from manufacturer to manufacturer, and even from one blade to another made by an individual manufacturer, it rarely is the limiting factor in how sharp an edge most reedmakers achieve. The edge may almost always be improved by paying closer attention to those two surfaces - the flat side and the bevel - which intersect to form it. A really sharp edge results when the surfaces are really flat and really smooth right at the edge. The purpose of each of the steps that follow is to flatten and smooth those surfaces.
My preference is for a knife in which the blade may be removed from the handle, because it is easier to do both the initial work and the routine sharpening on a blade unencumbered with handle. It also enables you to use the entire surface of the sharpening stone, which improves the efficiency and economy of the use of that tool. In addition, it is frequently easier to carry the blade and handle separately in a tool case. Nevertheless, any knife, whether or not the handle is attached, may be put in shape and sharpened by following these steps.
First, sight along the edge of the blade from one end to the other. If it appears at all bowed or wavy it must be straightened before anything else is done. A good way to do this is to place the blade on a flat wooden board and tap it with a wooden mallet at the high spots. Keep checking for straightness, and continue to tap until it looks as though the blade is perfectly straight. Check also to see that the back side of the blade is straight along its width, that is, from the edge to the opposite side. Do not move to the next step until you are satisfied that the back side of the blade is as straight and flat as possible!
It is now time to move to the coarsest sharpening stone you intend to use. Make sure the surface is flat and covered with lubricating fluid, then place the flat side of the blade down on the stone. With your fingers spread evenly along the blade, and applying moderate pressure, rub the blade back and forth across the width of the stone at least 50 to 100 strokes. Although it doesn't seem to make a great deal of difference, I always make my strokes perpendicular to the line of the edge. This way the scratches made in the steel by the abrasive are perpendicular also, and I think the steel right at the edge will be stronger and less likely to bend or break.
Clean the blade and inspect the flat side carefully. If the blade was perfectly flat to start with, it will be uniformly colored, with visible scratch marks running parallel across its width. When you run your fingernail down the bevel, it will catch right at the edge on the "wire edge" or "burr" you turned up during the honing, and this will be true at any point along the edge. This is the sign that you are ready to move to the next finer stone.
Of course you will be working in the real world, so instead of that finished blade, your inspection will undoubtedly show that only a small area of the flat side has that uniform color with the parallel scratches. And only a fraction of that area is likely to be at the edge. Keep in mind that only that part which is at the edge matters, because it is right there that you must make the surface perfectly flat. Perhaps you now feel differently about whether you succeeded in tapping the blade flat, and would like to try again. Go ahead. It is much faster, when it can be done, to bend the blade flat than to grind it flat. It also saves a lot of wear on the blade, the stone, and your patience. Be gentle, though; hard, brittle steel may fracture or shatter if you're not! When you finish tapping, come back to the stone and rub until you really do have the perfection described in the paragraph above. This is the hardest step, because progress comes only slowly. The closer to finished you get, the longer it takes to get farther, because you always have more surface to grind. You soon will come to appreciate the wisdom of the Japanese edge tool makers, who slightly hollow the middle of the flat side of their blades, thereby tremendously reducing the surface area in contact with the stone which must be ground to give a perfectly flat surface at the edge.
Speaking of the Japanese, I consider their waterstones indispensable for this process. Perhaps it could be done with the oilstones with which we are all so familiar, but I, for one, don't have the patience for it. They cut far too slowly. I think this fact, coupled with our general ignorance of waterstones, probably explains why few reedmakers realize the full potential of single bevel knives. The surface of a waterstone is soft; it lets the individual grains of abrasive come loose and roll around under the steel, forming a paste with the water which really pulls the surface down on to the stone. This enables waterstones to cut much faster than oilstones while using finer grit sizes. Although the soft surface wears out of flat sooner than an oilstone, the waterstone is more easily flattened. In addition, the soft surface makes you far less likely to chip the edge of your blade as you work it. Japanese waterstones are available in a large variety of grit sizes, and the artificial ones, which work very well, are relatively cheap (coarse stones cost about $10-$12, and finishing stones are about $25-$45). 1 recommend getting one #1200 grit coarse stone and a #8000 grit finishing stone. These two are sufficient for most purposes, although a #800 grit coarse stone can considerably speed up the initial flattening process.
Once you are certain that the surface of the flat side is ground flat all along the edge, clean the blade and move to the next finer stone. If you started with the #800 grit, move to the #1200, and hone until you have perfectly uniform color and (finer) scratches all along the surface at the edge. The surface is now flat, but not perfectly smooth.
Now move to the #8000 grit finishing stone and give it approximately 200 strokes. If you haven't cheated and left a coarse stone too soon (and if you've conscientiously kept your stone surfaces flat) the back of your blade should be polished like a mirror all along the edge. This is precisely the flat, smooth surface we're looking for.
Next, repeat the coarse honing on the bevel side. Be sure to hold the bevel as flat as possible on the surface of the stone. Instead of moving back and forth, start each stroke at the edge of the stone nearest you, and push the blade away, edge first. Do not pull it back on the stone's surface! Doing that will virtually guarantee a round bevel and a round edge, because you will rock the bevel changing directions. I recommend that on the bevel side you keep your hands at each end of the blade. This way any deviation from a perfectly straight edge in the finished blade will result in one with a very slight convex curve. Straight is fine, but concave is disaster, and a convex curve gives you a little more control of your scraping than a straight edge. Again, do not leave the coarse stone until the surface of the bevel is being uniformly ground at the edge. At this point, clean the blade and move to the next finer stone. After the #1200 stone, approximately 50 to 100 strokes on the #8000 grit finishing stone should give you a polished bevel surface.
If you now slide your fingernail down the flat surface off the edge, you should feel it catch, as you should now have a burr or wire edge on the flat side. Your blade is not sharp until you clean that up. Place the blade, flat side down, on the finishing stone, and give it about 10 strokes. Turn it over, and give it a single stroke on the bevel. Back to the flat side; give it one stroke (back and forth). Now to the bevel for a single stroke. Alternate 4 or 5 times, ending with the bevel stroke. Clean and dry the blade - it is now ready to go.
From this point on, keeping the single bevel knife very sharp is a snap. To sharpen, hone the bevel on the #1200 grit stone until you raise a wire edge on the back side. Clean the blade, polish the bevel on the finishing stone, then clean off the wire edge just as described above.
Before you write to me about how sharp your blade is when you leave the wire edge on, try scraping with a really refined edge like the one I've described - with both intersecting surfaces really flat and polished smooth. I think you'll like this better. (Please note, also, that recommend that the final stroke is a bevel stroke. This insures that if there is any bend at all in the steel at the edge it bends into the cane when you scrape.)
Some tips:
1. When you first inspect the blade, look at all the edges and corners. Only the sharp edge should be sharp. Your fingers and thumbs will be all over the others as you sharpen and scrape, so you may want to "soften" them with a file.
2. Once you have the back surface finished, hone it only on the finishing stone as part of the removal of the burr. You put a lot of work into getting it flat and smooth, so don't make more work for yourself.
3. Don't get preoccupied thinking about the edge. Instead, concentrate on the two surfaces which form the edge. If you make them really flat and smooth right where they come together you will get a great edge.
4. When putting the blade on any surface, always place the bevel side down. That keeps the edge up, out of harm's way.
5. Remember that cane is abrasive. As you scrape your reed, it abrades your knife. Thus you will find sharpening easier if you do it often, before the cane can materially change the shape of the surfaces at the edge. Of course your reed making should go better also if you always use a very sharp knife.
6. Never lift the bevel surface off the stone and hone only the edge in order to get a "quick" edge. As soon as you do that, you lose the advantage of having a surface to keep your honing angle constant, and you will have to take off much more steel when you decide to return to the method that always gives you a sharp edge.
A fine single bevel knife may be made from a Sears 6 inch jointer blade. Simply grind away the steel from the edge about 1/4 inch in for a distance of about an inch and a quarter from one end. (Note: single bevel knives are right or left-handed. Whenever you scrape away from your body, the flat side should lead, and the bevel side should be toward you.) Place the resulting tang in a Sears adjustable file handle, and away you go.
Two fine tool importing companies carry single bevel blades of my design which are made in Japan, and which also may be used with the Sears adjustable file handle. These feature the slight hollow in the flat side, an exceptionally hard steel edge, and a lamination with a softer steel on the bevel side which gives the blade additional toughness. These companies are:
WOODLINE The Japan Woodworker
1731 Clement Avenue
Alameda, California 94501
(415) 521-1810
and
Mahogany Masterpieces
RFD 1, Wing Road
Suncook, New Hampshire 03275
(603) 736-8227
These companies are also good sources for Japanese waterstones.
About the writer...
Stuart Mitchell is an oboist living in Minneapolis. Besides free-lance work, he holds principal oboe positions in two community orchestras, and is a founding member of the professional ensemble Harmonia Mundi (a double woodwind quintet with keyboard). Mr. Mitchell is also an economist on the staff of the Minnesota Public Utilities Commission, and he enjoys woodworking when he has time.