Some things that will cause a pie dough to become thick and tough are: - Adding too much flour to your workspace. Only add enough flour to avoid the dough sticking to your surface.  - Melted or soft butter. You want your butter to remain as cold as possible throughout the entire process. You can even put your butter in a freezer for 10 minutes before using it if you are working in a warm room. - Not rolling the dough thin enough. You want to make sure the dough is nice and thin, about 1/8 inch thick all the way around.