1)? Apply enough plumber's Teflon tape to the spindle to make it quite difficult, but not impossible, to tighten the chuck against its stop;
2)? Take many light cuts;?
3)? Run slow enough to be able to intervene and stop the chuck when/if it starts to back off the spindle.
This has worked well enough for me, used very occasionally on my 1961 SB9A, to forestall the need to spend huge money on an alternative (stronger) system.
