Depending on how homogeneous you want your grind, you may want to consider placing your cubed meat in the freezer for 30 minutes before grinding. This helps the product stay stiff as it goes through the die, and lets the mix be a bit more "even" between meat and fat (versus pate-like, which will have a gritty texture when cooked).

Also, consider dropping an ice cube in every 3 to 4 minutes of grinding. The blade can heat up significantly and cause fat smearing (meaning more fat is left on the walls of the grinder than mixed in with your meat).

For home-ground meat, especially for a ragu, I'd use a mix of chuck and brisket for the beef component, and shoulder for the pork. One item to remember is that Italian beef tends to be much, much heavier in the "iron" flavor (some call it liver); you can fool a Bolognese snob with a little bit of liver mixed in with your grind. If you can, some quality leaf lard mixed in with the beef fat will compliment the ground meat flavor nicely and create a more "complete" flavor package.

Cheers,

-Andrew