Reaper,
Highly simplified response to your comments and question.
Each type of tool steel has a range of hardnesses it can be hardened and tempered to and as you indicate with the example of the Axe, you can have two (or more) different hardnesses in the same finished tool.
Differential hardening is easier to do with water and oil quenching hardenable tool steels but does happen to some smaller degree with the air hardening tools steels which tend to be much more homogeneous in the heat treat because the quench time isn't quite so critical.
While on the topic of hardnesses, they are many wrong ways to get the "correct" Rockwell hardness scale reading that result in a steel not being as good as it could be. Rockwell hardness is a test to be used in the shop under controlled heat treat conditions in order to be understood and used well.
The Japanese sword smiths, who mastered the craft well over 700 years ago, may not have understood the science of what they did but they fully understood the process that produced the best results and did it very well.
Remember, this is when all steel was "hand made" with charcoal fired melts and forges way before big power sources and mills.
Swatsurgeon, Yes we have modern makers of traditional sword making techniques that are doing very good work.
Yoshindo Yoshihara (check this next link out!)
http://www.legacyswords.com/Yoshiharanihonto.htm from Japan comes to mind. My friend Bob Lum (knifemaker) met with him last week in New York City at the big knife show there.
Note the well defined differential hardening in the images.
Note the price the set of swords sold for at the end.