Old shapers had one, two or three wing cutters held by two flat collars screwed down tight with a nut. Some experienced woodworkers cut and shaped their own cutter blades to match a specific design.
In the early '70's, I was in a shop when a worker turned the shaper on after changing the blades and one of the cutters flew out and hit him in the shoulder doing considerable damage.
I would never use these type cutter heads after that accident. I wanted cutters with a center hole only and I was always more careful around a shaper after I saw the accident.
For my little shop, the worse thing is someone walking right up to me when I don't see or hear and making me jump. No accidents, just a surprise. Surprise is not good around moving blades.
Pet peeve: Someone walking in with a cold drink and setting it on one of my machine tables. Ahhh!!!
If you don't have time to do it right the first time, when will you have time to do it over?