I’ve caught myself running mine without the guard. I haven’t broken a wheel, but the thought of it made me change tactics.
Sometimes I run it with a sanding disc and no guard, but the naked whizz-wheel is a no no.
I see body guys running the open 3” ones on a die grinder all the time.
I used to way back when. Another fragged wheel cured me. Nothing happened but the shrapnel of it flying around the room gave me religion.
When I cut myself, I was extremely lucky my hand took the hit as it would have made a nice cut in my abdomen. I already have enough Doctor caused scars there. Didn’t need another ;)
It’s incredible what 10,000 RPM is capable of when it’s not doing what it’s supposed to be doing.
I’ve had both the good Makita/DeWalt wheels come apart as well as the cheap Chinese ones. It’s not that I bound them up or bounced them either. But since my metalworking days are over, I am just glad to get done with all digits relatively intact.