The first graphite grading scale is a numeric scale. Using this scale, the hardness of the core is often marked on the … 展开

The second graphite grading scale is known as the HB scale. Most pencil manufacturers outside of the U.S. use this scale, using the letter “H” to indicate a hard pencil. Likewise, a pencil maker might use the letter “B” to d… 展开

Generally, an HB grade about the middle of the scale is considered to be equivalent to a #2 pencil using the U.S. numbering system. In reality however, there is no specific industry standard for the darkness of the mark to b… 展开