One time when I was younger, I applied for a machinist job, thinking my hobby knowledge would serve me well, but it was a pump manufacturer and I was out of my element and failed badly. They hired me with the promise of easing me in but that went out the window in short order (and I know perfectly why and it's understandable, in hindsight). I could cut small gears on my own equipment, doing the calculations and building my own fixtures, but that was with no pressure, time line, and no-one looking over my shoulder in my basement shop.