I did some basic testing with a few farriers rasps a few years ago, this is what I found at the time:
I took 4 different makes of 14 inch farriers rasps and measured the Rc at the tip end and the handle end:
Save Edge 66 Tip 61 Handle
Bassoli 65 44
Mercury 55 41
Hellier 44 39
Next I sawed off the tangs. Except for the Mercury on which I used a cutting disk, the tangs were all soft enough to be hacksawed easily. I used the tangs as I wont need them to make knives and any case hardening is less likely to be present. I filed groves in each tang for identification and ground the surface of each side to remove any case hardened layer.
First I heated them to 825C, soaked for 10 minutes and quenched in oil. Hardness was as below
Save Edge 46
Bassoli 56
Mercury 23
Hellier 18
I then re-heated them all to 840C and quenched in water. Hardness was:
Save Edge 56 - 63
Bassoli 61 - 63
Mercury 50 - 56
Hellier 42 - 58
As you can see I did not get consistent hardness throughout each test piece. I am not sure why this is but I did not take to much time getting a good finish on the test pieces and they were just chucked in a bucket of water all together so quench was probably far from even.
I have made decent knives from the Save Edge and Bassoli Rasps but I do not anneal and re-harden them. I temper to the required hardness and grind them in this state. If you have a decent grinder this is OK except when you come to drill pin holes in the tang. If you stick to small pins 1/8" carbide bits are not that expensive and will go through a hard file OK. Grind off the teeth where you are going to drill otherwise they can deflect and shatter your carbide drill.
Hope this helps, file knives are great fun - hope yours comes out OK