I was making a dovetail cutter. Everything lined up nice.
Decided to drill all the way through but my chuck was butting up against the backside of the dovetail cutter. I was using a screw machine drill bit, 3/32". Almost got through, in fact I popped a little hole on the underside. Had to switch to a jobber length. As soon as I drove the bit down it broke. After I realized the y axis had moved .0005". Must've been just enough to cause it to break.