On Fri, 8 Jul 2016 11:32:36 -0400, "G. Ross"
wrote:
One of my early experiments with the vac chuck the first time I hade a
thin platter reversed... I didn't know that I should have a vac bleed
and pulled the center right out of the bowl... I had the tailstock
snugged against it, so it just played hula hoop until I shut the lathe
off...

Several years ago I had finished an 8" bowl top and had it in the Cole
Jaws finish turning the bottom. The bowl came loose from the little
rubber buttons. The tool rest interfered with it popping off so the
cole jaws just gave it a fling. It departed the lathe in a
hurry--striking the ceiling behind me. It ricocheted into the far
wall, came back and bounced off the table saw and landed at my feet.
That day I ordered a vacuum pump and started setting up my vacuum
chuck. Never lost another bowl that way. I wondered what would
happen if there was a power failure but it never has happened. I
found out what happens one day. I had finished a bowl bottom and in a
Senior Moment I got the sequence wrong and turned off the vacuum pump
before turning off the lathe. The bowl just dropped off the chuck
onto the ways. No excitement--no damage.

My other "Poor man's stress test" happened while hollowing out a vase
with a Forstner bit. The bit was held in a Jacob's chuck on a taper
which fit into the tailstock. Forstner bits get hot and expand and
sometimes bind on withdrawal. I usually back out frequently, blow the
shavings out and cool the bit with compressed air.
While woolgathering I was cranking the tailstock to back the bit out.
What I failed to notice was that the bit was not backing but the
taper was coming out of the tailstock.
Suddenly there was a loud clatter-- the chuck and taper were slinging
around striking the ways every revolution. I was afraid to cross the
"throw line" to reach over and turn off the lathe. I ran out the back
door, came around the shop and threw the breaker for the lathe.
That is when I started using a draw bolt screwed into the taper and
ending on the other side of the tailstock with a washer and a nut.
Duh! I also wired in a stop button held to the right side of the ways
with a magnet. Very handy.

If something can go wrong it eventually does.