My first year in shop in high school..... The teacher, who was new, had went into the shop one day before the school year started and was checking out the equipment. He started the planer..... one blade flew out the infeed side, into the lumber stoage room, the other two went out the outfeed side, thru the roll up garage door. He actually quit that day, and had to be talked into coming back. Someone the year before had not properly tightened the screws upon reinstalling the blades.