knife hardness

[jackie]

how hard [ rockwell scale ]  is a knife if only a new nicholson file will make a slot in the blade.  when making a knife i usually after tempering the blade make a round or square slot just to stop where the blade is to be sharpened.  i just had a knife where i had to get a brand new nicholson to make the slot.  usually just been using some nicholson files that have been used for a while. the knife really has a sharp edge but is it too hard .  thanks for all the help members on trade gang have given me  jackie

[kbaknife]

I would suggest that this is about how you want it. You should NOT be able to readily file into a nicely hardened blade, even with a new file.
A new file might be able to accomplish the job, but it should be a little work.
A used and/or slightly worn file should really not be able to file into a properly hardened blade.
Right after quench - and before tempering - all I can manage to do is scrape off the quenching oil even with a fairly new file. A fairly sharp file will slide off of the edge like it was a piece of glass.
I'd say that cutting edge MIGHT be in the vicinity of 59-60. Possibly higher.