I have been using Rc files for a couple of years ....They are never going to be as precise as a RC tester but they should give a good indication once you get use to them.......If you have a known hardness test piece then that will help determine your accuracy.
The way I use them , I take them out of the box and use them randomly without first looking at the Rc hardness.....and I then seperate ones that cut from ones that dont....in theory this then gives me a working range of the hardness within 5 points. I seem to get pretty consistant results and so rely on what the file is telling me.
I have just hardened some 52100 and the files tell me the hardness is between 60 and 65.....(60 slides very easily..)...
I use the files to help determine my tempering hardness...for instance, for consistancy, I will stop tempering cycles when the 60 file just begins to scratch.
