Place oil in deep-fat fryer, insert deep-fat thermometer, and begin heating to 375 degrees F. Place 1/2 cup dredging flour in pie pan; set aside.
Mix cornmeal, 1/3 cup flour, and salt in 2-cup glass measure. Add milk, egg, and 2 tablespoons vegetable oil. Mix well and set aside.
Thread frankfurters onto wooden skewers. Roll in dredging flour to coat, shaking off excess. Dip frankfurters, one at a time, in cornmeal batter, then fry in 375 degree F oil until golden brown, about 2 to 3 minutes. Serve warm.