Try finding a machinist that wears jewelry. Either they have yet to learn a painful lesson or they will have learned it directly or indirectly (colleague, machinist friend). That's one thing you learn to respect in a hurry: no jewelry near rotating machinery.
And loose clothing, gloves, ties (I once saw a visiting salesguy almost lose his head in a demonstration lathe), in fact anything that can end up where you don't want it to.
Similar advisories hold for printing presses, farm equipment and so on. Printing presses are particularly nasty because they tend to be so spotless that you can't tell if they're rotating or not by looking at the surface.
