China classifies pencil lead hardness into 18 grades, from the softest 6B to the hardest 10H. Among these, 4B to 2H are general-purpose writing pencils for study and office use, with HB being the most commonly used for its balanced softness and hardness.
2H to 7H are hard-lead pencils for engineering drawing and multi-layer carbon copying. 8H, 9H, and 10H are the hardest, used for production records, carpentry drafting, and similar applications. 2B and 3B are dark-lead pencils for drawing and deepening engineering drawings. 4B, 5B, and 6B are for painting and sketching.
Mechanical Pencils
Mechanical pencils come in three types: twist-action, push-button, and rotate-to-advance. When choosing one, first inspect the exterior for fine workmanship — no cracks, no burrs. If the exterior is sound, test the lead advance mechanism. Pressing the tail cap should cause the three-jaw chuck to open and advance the lead smoothly. Each press should extend about 0.5–1 mm of lead. Standard lead refills are 60 mm long. A quality mechanical pencil should also have a floating lead-sleeve to protect the lead and prevent it from poking other objects.