Spindle runout, or tool runout, as it can also be called, is the inaccuracies that cause a tool (in a mill) or workpiece (in a lathe) to spin off the ideal axis. It’s very bad for tool life, so it’s good to know more about it.
Here's a Fab Lab Skill Builder video tutorial on how to use a dial test indicator to locate the center of a square or rectangular workpiece.
Swing Indicating may be "old hat" to more than a few readers of this blog, but we find in our CNC Fundamentals Workshops that many new and self-taught machinists have never used the technique before. Here's a brief Fab Lab tutorial on how to indicate the center of a hole.