I’m writing this in large part to justify the enormous expense of building my own CNC machine. I needed a wrench the day before flying off for a dive trip. The wrench needed to be sufficiently thin to slip between the body of the AI transmitter and the first stage of the regulator, and so I could not run down to Home Depot to buy one. With all other alternatives closed to me, I thought about the problem. Thirty minutes in CAD and CAM and six minutes of making chips, and I had the perfect little wrench for the job.