I worked for a jet engine parts mfr. for 2 years, and did the hardness testing, grains structure/polishing, and certs on the steel rings, that went in jet engines- including military F-15, F-16, F-18 fighters. My dad worked there for 42 years. Also have a Degree in Automotive Technology, built many automobile engines as a side business, using various internal parts- cast iron, forged steel, billet steel, cast steel, aluminum & titanium. A close friend owns a machine shop. Through experience and research, I learned the basics.