Sharpening
Properly sharpened tools are absolutely essential for successful woodworking. Sharpening can be done manually or with a machine, the goal being to restore the sharpness of a blunt cutting edge. This applies to planes, chisels and drill bits as well as to scissors or knives.
When sharpening a tool, its blade has to be held at a certain angle to the surface of the sharpening tool; the more precisely this angle is maintained, the better. In this way one side is
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beveled and the other remains flat. Coarse sharpening can be done with a 220 sharpening stone, a belt sander or a grinder. Using a wet grinding stone and operating the machine at a low to moderate speed is least wearing on the tools involved. Note that when doing the sharpening by machine the tool that is sharpened must never get too hot as this would cause it to lose its hardness. Overheating can be prevented by regularly cooling the tool in cold water. Continue sharpening until an even, sharp edge has formed. Sharpening by machine only serves to remove the worst defects. It is also possible to use an apparatus where the sharpening stone is moved manually by turning a handle.
2 To get a really sharp edge this rough-sharpening by hand must be followed by honing on good-quality sharpening stones. For honing it is extremely important to keep a precise angle. There are special holders called honing guides designed to help you move the tool that is to be sharpened at a constant angle to the surface of the sharpening stone. My honing guide consists of two parts set on a threaded bolt that grip the sides of the blade when the bolt is tightened (1).
Continue sharpening with increasingly finer stones. When you have finished flip the blade over (i.e. put it on its flat side) and remove the little burr which has formed during sharpening by moving the even surface of the blade in a circular motion (2). The last thing to do is to wipe the cutting edge against a piece of leather, with the beveled side of the blade facing upwards. Always use water to moisten Japanese stones and oil for Arkansas stones. Diamond and ceramic stones can be used with either water or oil. If you are into cleanliness, don't use oil. Water stones should best be stored in a water-covered container with lid. Dry stones ought to be moistened for at least ten minutes before use.
Sharpening stones are available in many different grits. For our purpose a 1000/6000 combination would be sufficient. To get an even sharper blade you could use an 8000 sharpening stone after that. Japanese sharpening stones such as King Stones are a good choice: although they are softer, they sharpen better than other stones. Sharpening stones wear off after some time and require flattening of their uneven surfaces. This is best done by rubbing the uneven sharpening stone against a very expensive diamond
sharpening stone. There is, however, another, cheaper method of doing this: putting a sheet of moist silicon-carbide sandpaper onto a sheet of glass; the sandpaper will stick to the glass and you can make the surface of the sharpening stone smooth and flat by moving it in circles over the sandpaper. Do so until the sharpening stone is beginning to stick to the sandpaper, which is when the stone's surface is flat again. Use 150to 180-grit sandpaper for rather coarse and 300to 600-grit sandpaper for an 8000 sharpening stone. Sandpaper wears off quickly and has to be replaced regularly. To sprinkle silicon-carbide powder onto a sheet of glass instead is not a good idea as the glass surface will wear out and become uneven.
Sharpening produces a thin layer of grease on the stone's surface, which gradually reduces the surface coarseness of the stone. This is why this layer needs to be washed off regularly if the original roughness is to be maintained. Instead of using sharpening stones it is also possible to use silicon-carbide sandpaper: just moisten it, put it on a sheet of glass and throw it away after use.
Alternatives for sharpening
When using a sharpening stone or a belt sander for roughsharpening a blade the tool's bevel remains flat (a). It also remains flat if it is held against the side of a grinding wheel. There is a drawback, though: sharpening with finer stones takes longer as the whole bevel area has to be worked. Honing a microbevel (b) is an excellent way of shortening the time required for sharpening. Hold the tool slightly steeper for this purpose.
When the blade of the tool is held against a grinding wheel (c) a hollow bevel will automatically be formed, the curve of which will depend on the diameter of the sharpening stone. There is, however, one drawback: as the blade gets weakened during sharpening - in particular when the diameter of the stone is rather small -, it can quite easily break under heavy-duty use. On the other hand there is the advantage of a smaller area that has to be sharpened by hand afterwards. If this is done with the front and the rear edge placed onto the whetstone, the blade will be in a relatively stable position so that even the use of a honing guide will become unnecessary (d). If the chisel is to be used for fine, light-duty work only, this is definitely a very fast method of sharpening that can only be recommended.
An alternative would be to round off parts of the tool bevel (e). This not only allows heavy-duty work to be carried out but is also a faster method as the bevel area that needs to be honed is relatively small.
Tormek Super Grind 2004
The Tormek Super Grind 2004 is a very good but also expensive motorized wet stone grinder. Its honing leather wheel will probably do away with any further need for sharpening on stones.
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c d