it all depends on what type of sausage you want to make...
for hotdogs and typical emulsified sausages you use a fine plate 1/8 to 3/16 inch (grind 1x or 2x) or you can even grind the meats in a kitchen machine with a rotating knife until you get a fine emulsified paste..
for Salami types and typical cured/air dried sausages you use the larger plates up to 3/8 inch or 10 mm.. and make sure you partly freeze the meat and fat to get a nice clean and rougher cut without smearing the paste ...
for our hamburgers and gyros I use the 3/8 inch plate..
food bloggin at http://oldjinks.blogspot.com/