The idea is that they are so hard, and keep such a fine edge, you don’t need to sharpen them as often equalling longer life.

The backs are actually hollowed out to help sharpen them. Too sharpen them you first sharpen the bevel and then lap the back. the steel is so hard that if they did not hollow the back lapping the back would take forever.
The hollow grindings are actually shaped so as you lap the back the hollows ‘move back’ from the bevel edge, giving you the two flat planes you want.

Now remember I don’t have any Japanese chisels so my understanding may be incorrect.

I mean a good edge is the intersection of two flat planes–the back and the bevel–so once you grind the chisel down to this hollow-ground area, the back is no longer flat and you will have an M-shaped cutting edge. I can’t personally justify the $50+ per chisel to know that after several years at best, I’ll have to buy new ones, or at least grind the fool out of the back to re-flatten it…

Just my 28.5 cents worth!! ;-D
Give me a shout (or an open-handed slap) at my email & let me know what’s up…

Great episode. Even funnier than “….let’s get ready to make a cutting board!”, or the laugh track on the jointer’s jumpin’ episode!

I really do like them though. The blade is awesome and holds an edge forever. But you have to like the feel of Japanese chisels, and they are basically all the same. So you either like them or you don’t.

Richard, I noticed this on a few chisels in the past. Unfortunately it just seems like some of these bits are either not running true, or they are simply too wide at their tip. In fact, I just had an email conversation with someone about this exact issue. Here’s was what Neal suggested:
“To fix the problem of the protruding mortise bit, I chucked the drill bit in my drill press and adjusted it so the spur just penetrated my wooden table to stabilize the tip. I then carefully held a file against the edge of the bit. I followed this up with some sandpaper. Success! I don’t have enough experience with the tool to tell if it’s harder to press the chisel into the wood, but the sides of the mortise are much cleaner.”

It goes without saying that you should be very careful with this procedure. But with some caution and a light touch, it seems reasonably safe. To make it a bit safer, you might want to clamp a block of wood to the table and pivot the file from the piece of wood, kind of like the pin on a router table. Just something to consider.

Thanks for this episode. It was perfect timing for a project I’m working on. Once again you have saved me from making a mistake (or at least from spending a lot of wasted time trying to get things they way I wanted them)!