For all kinds of bowl-shaped or convex surfaces in wood.
The same tool from another perspective.
To sharpen we recommend the contoured Japanese water stones designed for sculpting and woodcarving tools. To sharpen the outer bevel, use the big stone formed for different wood carving tools. To grind the flat side (here the inner side, over the bevelled edge), we recommend that, due to the unique form of this tool, you find a section of stone whose form fits the convex surface, and then cut off a small piece. The water stone can be cut with a disposable hacksaw blade.