Why is drilling an ellipse?

Hello, your company has also done some technical public relations. Let's talk about what we have done first. My personal thoughts are: whether the drill core is eccentric, whether the drill shaft is coaxial with the drill sleeve shaft, whether the drill sleeve length is too short, whether the drill bit is perpendicular to the machining plane, and whether the machined parts have carbon deviation (machining hard spots). See the original post >>