If your seal knife blade gets chipped, usually from trying to cut a very hard stone, the traditional method to repair it is to have a piece of sandpaper handy to grind out the chip. I prefer more modern methods and tools made specifically for resharpening flat chisels. Get a whetstone, perhaps a double-sided one with course grit on one side and smooth grit on the other, and, if you are serious about reproducing the angle of the original beve, get a small chisel holder designed to roll across the whetstone, holding the blade at a chosen precise angle. You should keep your chisels sharp at all times; a chisel with a chipped edge will give unpredictable results when cutting. If you are unfamiliar or uncomfortable in re-grinding your own blade, or if you don’t have the tools available, a cutlery store or someone who has used hand tools quite a bit should be able to do it for you.
Repairing a Seal Knife
Written by Lu