The Sensuous Gadgeteer
(Page 4 of 11)
September/October 1973
By the Mother Earth News editors
Keep your knife sharp. You will not get cut on a sharp knife because the sharp edge enters the work and grips it. You will get cut on a dull knife because it will lose its grip on the work and slip out of control. Razor-sharp may be too sharp for some purposes, but because you have to work hard to get a knife razor-sharp, don't worry about it at first.
RELATED CONTENT
Hollow grinding a blade is cutting a concave surface in a blade. Razors and kitchen knives are hollow ground. Hollow grinding can be done only on a grinding wheel, so if you have only flat sharpening stones you can't get hollow grinding. Hollow ground blades have the property of taking a very sharp edge (because they are very thin) and of being easy to re-sharpen for that reason. Hollow ground knives are also fragile, for the same reason, and are best for cutting meat, vegetables, and hair, not wood and plastic. If you want to hollow grind your knife edges, it can be done on a big, slow-sharpening wheel. (NOT one of the fast, coarse, small shop-grinding wheels.) Turn the wheel and hold the knife against it.
When you finish using a coarser stone wipe the knife with a rag to avoid carrying the coarse grit to the finer stone. Wrap the rag around the BACK of the knife to avoid cutting the rag and possibly your hand.
When the knife is sharp, carve something with it. A strenuous but rewarding exercise is to carve out of a single block of wood the ball in the cage that you drew earlier. To do this will require some knowledge of wood and woods.
WOOD AND WOODS
The sculptor Robert Engman says, "The best use of wood is the tree," because in the form of a tree the qualities of the wood are put to use in the most efficient way, and all the properties of the wood are used. Wood conducts sap, and it bears weight. It resists attacks by insects and fungi. When we cut down a tree to take advantage of its weight-bearing properties (and its beauty) we must keep it healthy by replacing with oil the sap that is no longer available to it.
The living part of the tree is a cylinder of living tissue just below the bark and the tree grows as this tissue dies at its inner surface and cells multiply at its outer surface. Thus the major part of the weight of any tree is dead tissue—the wood. Wood is composed of fibers than run parallel to the axis of the tree. Because the growth of the tree runs in annual cycles, the wood fibers do not grow at a uniform rate throughout the year, and the wood shows annual growth rings. These rings (or annuli) which we see at the end of a cut log or branch are really cylinders of fibers that run the length of the wood, and in a cut piece of wood they are called the grain.
Two major traumas occur in the grain when the tree is cut down and sawed into blocks or timbers or boards. First, trees seldom grow absolutely vertical, so that the wood grows under the stress of the weight of the tree. When the tree is cut, its weight no longer rests on the grain, and the grain itself becomes stressed. Second, when the tree is cut into boards or blocks the cylindrical balance of fiber stresses is further disturbed. When water lubricates the wood so that the fibers can move past each other, this stressing results in warping if the wood is soft or thin, and in cracking if the wood is hard or thick.
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