It depends on the specific type of juicer that you have. Some press products are capable of grinding harder substances than others, so it’s important that you check to make sure according to the certain speculations that are on the product.
Most high quality automatic commercial juicers are capable of grinding smaller and harder substances, since they have a mediated operation that’s produces a strong and consistent pressure. But most manual commercial juicers aren’t capable of grinding harder substances, since they require you to push down a lever in order to extract juice from foods.
That being said, some common types of foods that people tend to juice are softer fruits and vegetables. Some even add herbs and spices to their juice as well, since this doesn’t usually affect the consistency of the juice while still adding more flavor.