Merk,
You also need to consider the subtle hardness differences (4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H).
Have you considered a Kuru Toga? "The Kuru Toga sets itself apart with an internal mechanism that slightly rotates the lead every time you write, making sure that you’re always presenting the sharpest possible line to the page".