How to Polish and Sharpen Japanese Chisels (Nomi) for a Perfect Cutting Edge

Before polishing, always resurface your finishing stone to make sure it’s flatter than your medium-grit stone. A perfectly flat stone guarantees even contact with the cutting edge and prevents the blade from rocking or creating uneven spots. If the surface is even slightly hollow or convex, the chisel’s edge will not polish consistently.

To flatten the finishing stone, many woodworkers use a diamond plate, a flattening stone, or even another coarse waterstone. Whichever method you choose, the goal is the same: remove the high spots and restore a smooth, level surface that allows the tool to make consistent contact.

Once resurfaced, use a dressing stone (also called a nagura stone) to raise slurry on the surface. This slurry acts like a fine abrasive, helping to polish the edge evenly. A good slurry indicates that your finishing stone is working as intended, giving you better control over the polishing process.

For the best results, gather the slurry evenly across the stone and keep it moist with a few drops of water as you work. This ensures that the stone cuts consistently and doesn’t dry out, which can cause scratches or uneven polishing.

Begin polishing the backside of the chisel on the finishing stone. At first, burrs will often curl over to the bevel side, which is perfectly normal and nothing to worry about. 

When working on the backside, the most important point is to keep your strokes light and controlled. The finishing stone and slurry provide all the cutting power you need, so pressing harder will not speed things up. In fact, applying too much pressure can create uneven wear, scratch the surface, or even cause the blade to rock slightly, which defeats the purpose of polishing.

Make sure to use the entire surface of the stone, moving the chisel across different areas rather than staying in one spot. This not only evens out the stone’s wear but also ensures the backside of the blade stays flat. A flat backside is essential because it forms one half of the cutting edge—if it isn’t properly maintained, the edge can never be truly sharp.

It’s also a good habit to pause occasionally and check the feel of the surface with your fingertips or observe the pattern left by the slurry. These small checks will tell you whether the contact is even and whether the burrs are gradually being removed.

Now, polish the bevel using short, controlled strokes. Short strokes make it much easier to maintain a consistent angle, which is critical at this stage of sharpening. If the angle drifts, even slightly, you risk rounding the bevel or missing the very edge where the burrs need to be removed. A stable angle also ensures the edge develops evenly across the entire width of the blade.

Here’s a useful trick: check for dark streaks forming in the slurry. These streaks are made of fine steel particles and show that the cutting edge is in full contact with the surface of the stone. If you don’t see them, it usually means the blade is tilted or lifted slightly, and the burrs will remain no matter how long you polish. By keeping an eye on these marks, you gain immediate feedback about your technique—almost like the stone itself is telling you whether you’re on track.

It can take a little practice to recognise these streaks, especially if the slurry is thin. If you’re unsure, try adjusting the pressure very lightly or shifting the blade angle a fraction until you see the dark lines appear. Once you notice them consistently, you’ll know your cutting edge is making proper contact and the burrs are gradually being polished away.

Switch between polishing the backside and the bevel a few times. Alternating in this way helps you gradually work the burr back and forth until it detaches completely, instead of letting it fold stubbornly onto one side. Each pass removes a little more steel, bringing the edge closer to its final, balanced state.

As you polish, gather the slurry back toward the centre of the stone and keep it moist with the occasional drop of water. Slurry is what does most of the polishing at this stage, and if it dries out or spreads too thin, it loses its effectiveness. By regrouping it and refreshing it with water, you ensure the stone continues cutting evenly without leaving scratch marks.

The process may take several passes, especially if you are working with a blade that hasn’t been sharpened in a while. Be patient—rushing can cause uneven polishing or leave burrs clinging to the edge. Over time you’ll notice the coarse scratches left by the medium stone become finer and more uniform, and the edge itself will look clean and consistent from corner to corner. This even, refined surface is your sign that the burrs are finally gone and the tool is ready for use.

To confirm that your chisel is truly sharp, it’s important to test the edge rather than relying on appearance alone. A blade can look polished and neat but still carry tiny burrs or a rounded edge that weakens its cutting power. These simple tests give you immediate feedback and help ensure that the tool is ready for precise work.