How does iron sharpen iron?

Sharpening Japanese chisels

Special features of Japanese chisels

Japanese chisels are made of laminated steel, a hard layer for the cutting edge and a softer, elastic layer as the carrier material. The mirror side is ground hollow to make it easier to peel off. The blade is slightly angled so that deeper holes can be chiseled than the short length of the blade seems to suggest. Due to the significantly higher hardness of the steel than we are used to with European irons, the cutting edges are also a bit more sensitive. Avoid prying and rough handling.

Traditionally, Japanese chisels (OIRE NOMI) leave the manufacturer's premises neither sharpened nor with a fixed clamp. It is up to the user to first make the iron usable and thus his own. In the meantime, the manufacturers are ready to deliver the plane irons reasonably sharpened, so that the initial effort is significantly reduced.

Attach the steel clamp

The steel ring, called a ferrule, which holds the wooden handle together when the iron is struck, is only loosely attached. Put the clamp on so that approx. 1 - 2 mm of the end of the handle is visible at the back. The ferrule will usually be too tight, file or plane a little from the handle until you can slide it open. If it is just a little too tight, you can compress the wood with a hammer on the anvil.

After the clamp has been pulled over the end of the handle, you can hit it down a little with the hammer. Then work the edge of the end of the handle with a hammer so that it lies mushroom-shaped over the clamp - which is thus permanently attached. You can make your work easier by immersing the end of the handle in water for several minutes after attaching the clamp, and only then work on it with a hammer. Some manufacturers have started doing this work in the factory. Then you don't need to do it anymore.

You can confidently hit the OIRE NOMI with an iron hammer - that's the way it is in Japan! It is important that so much wood remains behind that under no circumstances does steel hit steel!

Sharpening the iron

Under no circumstances use dry-running sharpening machines! Wet grinding machines are also only suitable to a limited extent for these irons, as they create a hollow bevel - the cutting edge is thus weakened. Japanese water stones are best!

First smooth the mirror side! This is absolutely necessary with new chisels! Place the iron with the mirror side flat on the grinding surface (a completely flat sharpening stone or a steel plate sprinkled wet with silicon carbide powder!) And move the iron on this surface until you notice a removal in the entire area of ​​the cutting edge. Do not grind too much from the mirror side, otherwise you will reduce the hollow bevel too much, which will make it difficult to remove later.

Then the bevel is ground on a water stone with a grain size of 800 to 1200. The correct bevel angle is somewhat more obtuse with Japanese irons than with European ones. Take approx. 30 ° for softwood, for hardwood processing you can go over it - up to 35 °.

Hold the iron with your right hand. Press several fingers of your left hand (depending on the width of the iron) on the mirror side of the iron at the very bottom of the bevel so that its surface rests firmly on the whetstone. You can use your thumb to support the iron from below. You will get the best cutting edge if the cutting edge is at right angles or up to 30 ° at an angle to the grinding direction.

The following applies to narrow chisels where the cutting edge is narrower than the length of the bevel: Hold these chisels as far back as possible on the handle with your right hand and move them back and forth with the cutting edge while sharpening. It is perfectly legitimate to use a grinding guide and is highly recommended for beginners. Sharpen until there is a fine burr on the cutting edge.

Now - but not before - you can start honing the cutting edge. Use a grindstone with a grain size between 3000 and 8000 and process the bevel and mirror side several times, alternately, just like in the previous grinding process. The burr falls off and the bevel and mirror side become more and more shiny and thus sharper as the peeling process progresses.

Make sure to dry the iron carefully after sharpening and to oil it lightly before storing it in order to avoid corrosion. Then you can enjoy your precious tool for a long time.