Dry or wet grinding?
Do not use a dry grinding machine to sharpen your good chisels and plane irons made of carbon steel. The heat generated leads to a loss of hardness, significantly reducing the tool’s lifespan. A common misconception is that this does not occur if you remove the tool from the fast-rotating grinding wheel in time, before it turns blue, and dip it in water. A structural transformation occurs at significantly lower temperatures. You cannot control this process. Complaints about supposedly poor steel quality of tools, whose good quality I knew, were always due to treatment with dry grinding machines. Slow-running wet grinding machines (about 90 to 120 revolutions per minute) prevent heat buildup. They grind slower than dry grinding machines, but they ensure the proper treatment of your tools. The best on the market are based on a sophisticated system and are manufactured by the company TORMEK in Sweden. However, the acquisition costs exceed many budgets.
With good sharpening stones, a grinding guide, and some practice, you can achieve the best results. By sharpening by hand, you get to know your tool best and remain independent from the usually stationary machine. Besides, a grinding machine is of no use to you if you want to flatten the back of your plane iron. For that, you need a flat surface, which a round-running machine cannot provide.

There are differing opinions on whether the bevel of a tool should be better hollow-ground, as with machine grinding, or better flat as with hand sharpening on a sharpening stone. The hollow grind makes subsequent honing easier, but the resulting sharper angle weakens the edge and makes it more prone to chipping. This is particularly noticeable with the very hard laminated Japanese irons. In Japan, it is unthinkable to hollow grind the bevel of a plane iron. The grinding recommendation for plane irons from the manufacturer E.C.E. clearly opposes hollow grinding. If you opt for a flat bevel on your plane irons or chisels, you are in good company.

Water stone or oil stone?
Many stones can be used effectively with both water and oil. However, once the choice is made for oil on a stone, it can no longer be used with water. The mineral oil used is not particularly healthy for the skin, which is why I prefer water stones. Due to their superior qualities, Japanese water stones are increasingly being adopted.

The soft Japanese water stones should only be used with water. They allow for effective sharpening, as the loose binding continually releases new abrasive particles. It is sufficient to soak them in water for five to ten minutes before sharpening. It is less advisable to leave them in water constantly, as a slimy layer forms on the surface, or, in some cases, the surface disintegrates.

However, these stones hollow out faster than hard stones and must therefore be re-flattened regularly. This can be done quickly with the following method: You need waterproof sandpaper grit 80 and finer, a smooth surface as a base, ideally a glass plate, and – if you want it to go even faster – a can of silicon carbide powder. A puddle of water on the glass plate to hold the sandpaper firmly, a bit more water, and a teaspoon of silicon carbide powder on the paper, move the stone on it with little pressure – and within a few minutes, it is perfectly flattened.

As a basic setup, it is advisable to have: a sharpening stone with grit 700 – 1200, a honing stone with grit 3000 – 6000, a grinding guide. As a supplement, a coarse stone with grit 120 – 400 is recommended. If plane irons are also to be sharpened with the grinding guide, the stone should be a few millimeters wider than the widest iron. Sharpening and honing stones are also available as combination stones.

It is known that many stainless steels, especially stainless steel knives, are very difficult to sharpen. Even Japanese water stones occasionally reach their limits and become clogged. However, this is not a big issue, as they can be quickly cleaned using the re-flattening method described above. If you have such knives or chisels, a visit to the Missarka artificial stones is worthwhile.