John K Jordan
I use four CBN wheels (different grits) for all woodturning tools.
No problem with hardened steel. I've ground mild steel many times and without loading the wheels, but sparingly and gently. Good question about the laminated blades - I suspect they will be OK but maybe try it. Unlike serious metal shaping, in sharpening a plane iron you will be removing very little metal.
Flat workers on another forum have been buying CBN wheels for chisels and planes and such. Maybe there is some experience now.