Start spinning the square stock through the 1/2 holes and into the router bit. This is where the fine tuning comes into play. If you're blade is set even just a little too close, it will still make it through the output guides, but your shaft will come out looking all crazy, rough, and wavy. If it's set too far out, the square stock won't go through the output holes effectively and will build up excessive heat.
You want it to cut just baaaaarely larger than your output hole... And I'll elaborate further with pictures