I use the old style hand crank unit, as the motorized ones can tend to get warm/hot. Since deer is so lean, you will need to add some fat. IMHO, this really needs to be kept near frozen or your sausage will taste like the grease catcher at your local fast-food place. Go slow, if the meat coming out of the grinder starts to get warm, toss the hole thing back into the freezer for a few minutes.
Dave T