Metal hardness having a bunch of different units is quite annoying but also interesting. There are quite a few ways to measure the hardness the most interestin

Metal hardness having a bunch of different units is quite annoying but also interesting. There are quite a few ways to measure the hardness the most interesting being Vickers. You plunge a diamond of a known force into a surface and measure the size of the indentation. This is surprisingly accurate but does leave a small diamond mark on your surface. With a sufficiently small part a blacksmith or other folks can determine the hardness of a steel just by listening to how it rings. Hey, you can also test for cracks with a ring test, the most common use is ring-testing a vitrified grinding wheel to see if there is no crack Alot of engineering is just listen and maybe the odd hit with a hammer