Yoshiharu H-4 Japanese wood carving knives, set of 4

Good material quality. One complaint though: I use one of the gouge to cut a 10 mm round baguette of basswood-nice and easy to work wood, and after 7-8 seconds of continous pressing against the wood, the gouge's edge got a little black-bluish spot due to heat friction. Don't know if this will affect in some way the blade's strength.