Years ago I was attempting to create a CD rack (bored) using an old 3/4"
piece of oak. I was going to dado some exact width slots in it for the CD's
to stand up and tilt in, using a table mounted router.
After about the third or fourth dado slot I found the router bit came right
up through the top (backside) of the piece. The router depth locking screw
came loose (or I forgot to tighten it) and the vibration from the table made
the router gear rack screw itself right up through the 3/4" depth of the
wood instead on holding a 3/8" depth slot. I never figured that was possible
until I was staring at the 30K RPM bit by my fingers.
Wasted piece of wood (made it shorter) but the lesson was a good one
learned. Nobody got hurt but I never (If I ever did?) put my hands over top
of the router bit, anymore, no matter how thick the piece is. Pusher sticks
and distance became paramount.
You know, I used to be about like anyone else, in that I never used a guard
on a table saw. That all changed 18 years ago, when I took a job teaching
carpentry at the local high school. It was made very clear to me that any
and all safety devices available were to be used, at all times.
For the first year or so I fussed under my breath, any time I had to run the
table saw with the guard in place. Slowly, I began to realize that they
really were not all that bad, in nearly all cases.
Now, I seldom think a second thought about the guards. The obvious
exception is when using a tenion jig, or dado blade or other or other cuts
that do not go all the way through the workpiece. Even then, there are
guards available for the second class of cuts mentioned above.
So really, if everyone just made up their mind to keep with a guard until
they got used to it, you would find that it is a rare case where the guard
slows them down or prevents accurate cutting.