The Japanese make their chisels with two layers of steel - one hard layer, to provide the blade, and a second, softer, springier one to carry it. The face of the chisel is hollow-ground, to make it easier to hone. The blade is angled slightly, so that it is possible to take out deeper holes than would appear from the short length of the blade. The steel being so much harder than we are used to in Europe, the blades are also more fragile than ours. Take care not to use them roughly or as levers.
A Japanese chisel (OIRE NOMI) is traditionally supplied ex-works neither sharpened nor fixed tight in its ferrule. It has always fallen to the user to convert it into a usable tool and thus make it his or her own. Nowadays the manufacturers have come round to supplying the chisels ready sharpened to a fine keenness with a resulting gain in time for the purchaser eager to use them.
On no account use a dry-running grinding machine. Even wet-running grinders are little suited to this tool, as the bevel they make is hollow and will weaken the cutting edge. The best thing to use is a Japanese waterstone.
Hold the chisel in your right hand. Push several fingers of your left hand (depending on the breadth of the tool) onto its face, right down by the bevel, so that its surface is pressed close and firm against the grinding stone. It is then possible to use your thumb to give the tool support from underneath. The best cutting edge is obtained by running the blade along the stone at either 90° or 30° to the direction of grinding. However, very narrow chisels (with cutting edge shorter than the length of the bevel) are an exception to this rule. Hold such tools in your right hand, as far back as possible on the handle, and while sharpening push them with the blade backwards and forwards. Using a grinding feed is perfectly legitimate - and is strongly recommended for beginners. Continue the sharpening process until a fine burr is produced on the edge.
Now - but not before - you can start actually to hone the blade. Take a stone with a grain size between 3000 and 8000, and grind the bevel and the flat face of the chisel alternately, several times, exactly as described above. The burr will fall away; the bevel and the face of the chisel will shine ever brighter as they become sharper and sharper.
Take care to dry the tool thoroughly after sharpening and, if then storing it, to oil it lightly so that corrosion does not set in. You will long have pleasure in your valuable tool.