I do not have access to a hardness tester now. Since I do have a lot of experience by now,I don't feel like blowing a lot of money to buy a new one for my home shop use. I have an accurate electric furnace for when I make punches or harden knives,or whatever. I can harden and temper at accurately controlled temperatures and get the hardness needed for punches and dies for my wife's jewelry business. Beyond that,I'd mostly be making guitars,which need no testing.
Rob is where I was many years ago,when I was new to toolmaking and curious about many things including tool hardness. If he wants to dabble to satisfy his own curiosity,let him do so. Beyond that,I can't see him making Earth shaking new discoveries. The work already has been done even if charts and graphs were not drawn.
Charts and graphs in the end prove nothing. They,like computers,only reflect what has been put into them.Producers of nearly everything from tooth paste to medicine can make graphs to prove their product is best.
Being able to file a Disston saw proves nothing,especially that they are in the low 50's RC. They are more into the 40-48(at most) range( a nod to David). I'm sure exceptions can be found,but the ones I tested were in the 40-45 range. I guess I should have written a book or done a dissertation about it. It didn't seem that important at the time. Nor does it now.