A gouge chisel is used for woodcarving. It has a semicircular end on it used to dig, cut or shave wood off to make curves and round indentations, and it can be used anywhere a circular or profiled shape is needed. With normal usage, the razor-like edge of the gouge chisel will dull. Normal files or flat sharpening stones will not work because of the round end on the gouge chisel. To properly sharpen a gouge chisel, use a rattail file.
Clamp the gouge chisel in a vice.
Place the file in the curved area of the chisel with the end of the file facing the wooden handle of the chisel.
Tip the file down at an approximately 30-degree angle. Lean down and look at the point where the file meets the angular edge of the chisel. Tip the file in the direction needed to match the angle on the chisel.
Push the file forward and back over the angle on the chisel. Pause for a minute to check your work. You should see bright, shiny marks where your file cut into the angle on the chisel.
File back and forth keeping the integrity of the chisel's original angle. File around the perimeter of the semicircle shape until the chisel's angle is consistently shiny and sharp all the way around.
There are different sizes of rattail files and different sizes of gouge chisels. Use the size that works the best for your file.
Wear safety glasses when working with or filing chisels.