I thought I would add a blog about my Japanese chisel handles. Everyone asks me if I have pounded the hell out of my chisels, and well, yes I have, but, the handles are not mushroomed because of this.
I actually mushroom the handle on purpose. This is done because the mallet used is metal. You don’t want to smash a metal mallet onto the metal ring near the end of the handle of the chisel. This would just trash the mallet quite quickly. So the wood of the handle is mushroomed over the ring to protect it and the mallet.
The Japanese mallets are made with two types of steel. The inside of the mallet is a softer iron, while the outside is a harder steel. This creates a mass that is similar to a dead blow hammer. It transfers more force into the chisel resulting in more effective cutting.