I recently picked up 3 large files at a flea market.  This afternoon I put them in my fire pit and with the help of a leaf blower got them cherry red.  My problem was that due to their size 12"-14", I couldn't get them cherry red all at once (in other words only one half at a time).  I thought I got them to non magnetic, but once they cool a little do they return to magnetic?  I put my magnet to them while in the fire and sometimes they wouldn't be magnetic, but I just checked them and they are completely magnetic again.  Do you think I got them hot enough?

I assume you are trying to soften them , they will become magnetic again . Take a good file and see if it will cut them , try in several places , this will tell you if they have softened .

Yes, I was doing the initial softening.  I'm going to let them set in the ashes over night and cool, then tomorrow I'll try a file on them.
Thanks