Over summer 2016, I operated a CNC mill (tabletop MDX-40 by Roland) at Keck Graduate Institute to create prototypes and testbeds for a medical device. It was a truly trial-and-error, learn-as-you-go experience because my mentor had gone on vacation, so I overcame my steep learning curve with marathon sessions of machining videos, in addition to learning what not to do, i.e. ruining little pieces and examining each situation for nuggets of wisdom (because what else are mistakes good for?). I had kept a comprehensive notebook on all this knowledge so while I was typing them up for my long-term use, I decided to turn them into an instructable for other people as well.
CNC machining, Learning from [a lot] of mistakes, Getting used to having dirty hands