Dieter Schmid's Fine Tools
Japanese water stones and other Sharpening Tools

Sharpening Tools, Waterstones

Sharpening one's tools is an important part of the job for a woodworker - do not look on it simply as a necessary evil!

Should one grind wet or dry?

Never use a dry grinding wheel to sharpen your good chisels and plane irons made of carbon steel. The heat developed leads to loss of carbon so that they stay sharp for less time. It is a common misconception that this will not happen if you stop soon enough, before the iron starts to look blue, and take it away from the still-whizzing wheel to plunge it in water. There will be a denaturing process even at a much lower temperature. You have no way of checking what is going on.

With a good grindstone, a grinding feed and a certain amount of practice, your results will be of the very best. Sharpening by hand teaches one the most about one's tools and has the advantage of a taking place anywhere, while a machine is fixed. And, besides, a grinding wheel is useless when it comes to sharpening the back of your plane blades and chisels. For this, you need a flat surface and this is not available on a rotating wheel.

Opinions differ as to whether it is better to grind the bevel on a blade hollow, as happens on a grinding wheel, or flat, as happens in manual sharpening with a grindstone. Hollow grinding makes the subsequent finishing easier but the more acute angle which it causes will make the cutting edge weaker and more liable to break. This effect is particularly noticeable and disadvantageous with the very hard, laminated Japanese plane blades and chisels. It is unthinkable to grind the bevel of an iron hollow in Japan. The German manufacturer E.C.E gives a clear warning against hollow grinding. So if you decide on a flat bevel for your plane iron, you are in the best of company.

Waterstone or oilstone?

Many stones will give a good performance both with water and with oil. However if the choice has once fallen on oil, water is no longer a possibility. As the mineral oil one has to use is not particularly healthy, I prefer waterstones. Japanese waterstones are becoming more and more popular because of their superb quality.

Among the Japanese waterstones the soft ones favour efficient sharpening, as their loose composition means that new abrasive particles are constantly released. They only need to be put into water for five or ten minutes before they are used for sharpening. It is not wise to leave them in water all the time, because the result will be a slimy surface.

These stones do, however, become concave with use more quickly than harder stones and must therefore be trimmed into shape more often. The quick method of doing this is a flattening stone. A cheap alternative is to take wet-or-dry sandpaper (grain size 80 or so), a flat surface to rest on, (a sheet of glass is best), and - if you want to speed things up even more - a packet of silicon carbide powder, grain size 60 or 120.

Your basic kit should be: a sharpening stone of grain size 800 - 1200, a hone of grain size 3000 - 6000, and a honing guide. A coarse stone of grain size 120 - 400 is a useful complement to restore blades or to grind down notches. A combination stone is available in which there are both a sharpening stone and a hone.

Many tools made of stainless steel alloys, particularly stainless-steel knives, are very difficult to sharpen. Even Japanese waterstones will not work consistently in sharpening these knives, and will load up. All is not lost, however, because the stones can be quickly and easily dressed following the method described above. If you have stainless steel knives or chisels, you may wish to visit our page showing Missarka synthetic stones.

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