Hollow Chisel Mortiser |
Know safety, no injury. No safety, know injury. Unknown (but alas, true) |
I won't try to describe this better than Bob Van Dyke from the Connecticut Valley School of Woodworking and Fine Woodworking.
Bob authored this article with a nicely done video:
One note though: These tools should not be re-shaped. If that is needed, the bit should be replaced.
Lee Valley sells diamond sharpeners shaped like a cone (item number 77J8124) which can be quite useful for sharpening this tool.
Other companies may sell similar cones. Ensure the cone's shape is correct for the bit you are sharpening.