I've read a couple different books that touch on the topic, and the best publication I've found is an older Forest Service manual called "An Axe to Grind." It's available in pdf format from several places on the web, though the pictures were not complete in the first one I found. I have a copy of the whole thing, but all I can find links to now is this chapter by chapter page:
http://www.fs.fed.us/eng/php/library_card.php?p_num=9923%202823P

I have yet to enter the world of handle making, but I've got an excellent source for handles nearby, so I concentrate on mating the heads and the handles as well as I can... I like the idea of using hot sand. Will have to try that sometime.
Cheers,
Bill