Recently, when I was making the mast for "Lady Daphne", I was turning the bottom section from 20mm square ash.
Very successfully, I thought!

Because it was 24" long, I had done the chuck up pretty tightly.

Then I could not release the chuck easily with the two C spanners.

So I wedged the one spanner on the rest, positioned the other to give it a fairly hefty wollop with a rubber mallet in order to loosen it:-

Result:
I can still see it in slow motion! .... spanner left the chuck, rotated twice in mid air, before hitting front tooth via lip.

,broken front crown, bloody split lip, visit to dentist to remove sharp edges and pieces of tooth/crown from very swolloen lip and a bill for replacement of £177.

(That's NHS price)