craigd
David writes ..I've read the discussion with some interest, because I can't otherwise explain why my HSS planes last so many multiples longer
I could be blowing smoke but I believe that HHS is more rust/corrosion resistant than O1 which may possibly be a [probably quite small] factor. The more obvious factor is HSS was designed to be more durable in machining applications (as well as tolerating much higher heat, if heat is a factor).