Proper Disclosure – I own a Ceramic Coating Factory & Research Lab for over 2 years. This method won't tell you exactly what the BN is, but it will give you relative data.
File bullet/lead flat and smooth Hold the pencil at an angle and push across the lead If the pencil cuts a trough and leaves a curl of lead, the pencil is harder than the boolit lead "HB" (14-15 BHN) If the pencil slides across the lead the pencil is softer than the bullet lead "B" (13 BHN) This boolit is between 13 and 14 BHN Pencil Hardness Chart These were the standard for most mechanical pencils from when they were first invented until different lead sizes became available. Thanks for the request!
Thus, the “H” stands for hardness, and the “B” stands for blackness. The HB system is a way for manufacturers to rate the hardness and blackness of a pencil. Key difference: The main difference between an HB and B pencil is that the HB pencil is a medium range lead, whereas the B pencil has a softer lead.. A Pencil is a popular tool used for writing as well as drawing purposes.
The pencil hardness test, also referred to as the Wolff-Wilborn test, uses the varying hardness values of graphite pencils to evaluate a coating’s hardness. The pencil hardness directly effects how your picture will look and can even add some depth should you choose to keep the lighter lines after outlining with your softer lead. The pencil scale is a test of hardness that gives an impression on how hard a certain coating is. So, if you have some lead of unknown hardness, you start with the 6B and work up until the pencil curls it and you know approximately what you've got. If 6H won't curl it, it is probably zinc. If nothing else it will help keep your composition and paper free from lines that won’t fully erase because of the soft lead that has been ingrained into the paper too early. The test is done by pressing a pencil with a certain hardness firmly on the surface on a 45 degrees angle. The Elcometer 501 Pencil Hardness Tester has been designed to ensure that the cylindrical pencil lead is maintained at a constant angle of 45° and exerts a force of 7.5N (1.68lbF). The highest grade that does not make permantently mark the surface is the score for the pencil scale. January 27, 2018 Pencil Hardness, Mohs Scale, ASTM D3363, 9H & 10H Explanation Post about H – Hardness, Scales (Mohs Scale, Pencil Hardness), Standards (ASTM D3363 / ISO 15184) & Pencil Hardness test Pencils (9H/10H). If the pencil is vintage and you say 1.1mm leads don't stay and 1.3mm are too large, you're probably looking for a 1.18mm lead.