The handle in a throwing hawk should slip. This makes it less likely that the handle will break when you sink that head into a nice solid tree stump 45 feet away, or it smashes into flesh covered bone. The idea is the handle will slip out of the head on impact, rather than trying to absorb all that force. It works like a Pulaski or a pick axe, and can be fitted by a good sharp tug, assisted drop, or a straight swing.
The best place to find authentic hawks is a local rendezvous. Cold Steel makes relatively faithful machine made repros. A good hawk should not be very hard at all, it's designed as an impact weapon, and needs to be able to bounce off things. I still remember when I sunk a hawk into the tail end of another hawk head, and it stuck. I've split and stuck many handles, but this was the first time I'd ever stuck another hawk head. The blade edge was dinged, and the other hawk and a beautiful little nick in it. Man, ya'll are gonna make me buy a set of hawks now...
Stryver