SiGray mentions cutting tools, and this is a good point. Cutting tools are an issue both for machine tools and robots, (Yes, plenty of people use robots to cut things, more on that later).

Cutting tools are almost a black art. A simple mill may use a simple tool, some of the simplest (Like Bridgeport mills) just use collets directly in the spindle head. More complex mills use tapered holders which do their best to minimize the amount of runout the tool has, with more accurate tools requiring more stringent manufacturing processes. At a certain level the error introduced by clamping mechanisms and collets is inadequately innacurate, and hydraulics or heat are used to clamp tools into specially ground toolholders like Techniks

I know most of the players in the cutting tool industry, and I know men who I think are the very best at it, and one of those is a guy named Craig. Craig knows more about cutting tools than I will ever know about all the things i know about. As far as I am concerned, if you are not Craig, everything you think you know about cutting tools is wrong. And that’s beyond relatively simple things like tool wobble and vibration- the gyroscope effect, which in a properly constructed spindle cancels most of the unwanted BS out of properly constructed tools, is another whole discussion.