I've seen such an interesting tool first in the book "Das Drechslerwerk" by Fritz Spannagel. So, right a way I asked a good friend to weld me three chisels together. The result is shown in the photo. Why this tool is so useful should be clear to a wood turner: If we try to turn something from a wood stem or branch with it's core inside, usually it will split due to the drying process. If we use a simple wedge we can split halves or quarters. So we can chop two or four round pieces of timber. But if the threefold wedge comes into play we can win three wood pieces with bigger diameters and we have less shavings.