At the time, I thought that the blog was one I had discovered about a year ago, when looking for reviews of mechanical pencils. But it turns out I was in error. The blog I had found is Dave's Mechanical Pencils, which I discovered when trying to find a mechanical pencil similar to my Rotring Trio. I was also trying to figure out which kind of lead I prefer. I know I prefer to write in a 0.5 mm pencil, because I like the fine lines it can create, but I'm still discovering which softness or hardness of lead is best for me. I'm currently alternating between HB and B. I do like the lines, but the pencil lead breaks far too often for my taste as I'm writing.
Anyway, I bring this all up because I finally refound Dave's wonderful post, Dave's Mechanical Pencils: Lead Size & Hardness, which goes into detail on what the different sizes and hardness of pencil lead mean to you, the pencil end user. If you have any interest in this topic, check out the post and the blog.