Good morning, everyone.
A while back when I was prattling on about tool steels, I looked into the subject of hardness testing to see how the various Rockwell Hardness numbers were determined. What I found, was a huge can of worms that fits under the heading of ‘materials testing’ and rather more involved than I had anticipated, so I set it aside for another day. Good news! Since I’m somewhat unprepared this morning, today is that day, at least for hardness testing of metals.