Originally Posted by
Mike Blue
One other thing I could be curious about is your tempering temperature (the post hardening stress relieving aspect), that might lower the final hardness. But, if it skates a file, it's probably hard enough that it shouldn't be giving you so much trouble. Other factors are that scale can be hard sometimes and tempering the scale will make it seem much softer than the meat underneath.
This is where a keen observer will rise to his full strength. You're there with the blade in hand, while the rest of us depend on your description, times, temperatures etc. And, there are a lot of variables. Sounds like you're working a good program though.