I found a method that worked well for me... I used it on my Cold Steel Frontier Hawk with complete satisfaction (a thrower). In fact, I
never have the set-screw tightened...
Firstly, I fitted the head and haft...
To do this, I started with the head first... I basically just 'cleaned-up' the eye, and smoothed the eye opening, all with a medium-roughness file followed by emery cloth (removed the 'sloppiness' of the craftsmanship, basically). The haft fitting was done by sanding lightly by hand until the shape of the haft exterior matched the eye opening shape as well as possible.
I test-fitted the whole thing repeatedly as I went...
Finally, I put the head (but not the haft) out in the sun on a hot Summer afternoon for about an hour (it was about 100-105 degrees outside), and then slid the haft gently down into the eye opening till it was just snug. Quickly, before the head could cool-off, I loosely wrapped the fingers of my 'weak-side' hand around the top of the haft just under the head, and with my strong hand I 'whacked' the top end of the haft with a full-sized rubber mallet a few times.
This might work even better at the 'prescribed' temperature and time, however: 200 degrees 'F', for 20 minutes...