Tempering files?

[ALW]

How long, at what temperature, and how many times to you heat an old file to temper it?  I know this is kind of a loaded question.  

I made a makeshift forge last week to work on some knives.  I annealed a blade I had cut from an old gravely blade and did a small (old) nicholson file at the same time.  I finished up the gravely blade knife and heat treated it and tempered it in a toaster oven at about 375 degrees for an hour.  It seemed to work out fine and sharpened up good.  I hacked on a piece of hickory (seasoned) with it and it still held a pretty good edge.  

Now the file softened up really good and I shaped it and beveled the blade.  Then I reheated it and quenched it in warmed used motor oil.  It hardened back up.  Next I put it in the toaster oven at 400 degrees for about an hour and a half.  After it cooled I tried to work the bevel a little more and could barely cut it with a file.  So I repeated the tempering process again.  It seemed to cut a little better but it's still really hard.  Any help?  I seem to remember seeing a chart on here somewhere with times and temps. for tempering different steels but I can't seem to find it.

Thanks.  Aaron

[theunluckyhunter]

a file should slide off of a properly hardened blade.

when i do files i cook them at 375 for an hour then let it cool and repeat

[ALW]

Thanks.  Maybe I actually did do it right!  LOL...  I was just trying to clean some file marks out of the bevel with a newer file and figured it would at least cut enough to smooth them out.  But it just about skates off the blade.  

Thanks again.     Aaron