Trying to work out what was blocking my shop vac, dismantled it but left it plugged in so I could test it, put it upside down on the bench, touched the edge of the fan to see if it moved freely which rocked the whole unit onto its power switch and turned it on. The end of my finger got split open and the fan ate away at the insides. When having it put back together they were picking bits of bone out. Because it got opened out the outside bits went back together really well. No visible scarring at all, all the finger is shorter and a different shape. I put the vacuum back together a while later and found half my finger nail embedded in the fan.