Originally Posted by
IMT
My experience is that it DOES make a difference when you tighten all 3 key holes. Tighten one as much as you can with the key, then got to the next one and tighten it. I've found that it does move a little, go to the 3rd and it also moves a little. I've had an issue where a drill was slipping in the chuck after tightening only one key hole. Tightened all 3 and the job finished without slipping.
It isn't because the world is flat it's because steel isn't infinitely stiff. Friction and elasticity prevent the force on all the jaws being the same when tightened from one key hole.