There is an alternate approach. If your Craftex is similar to my Taiwanese lathe of a similar size the end of the spindle is threaded. You can make a cap with a 3/8"-16 through hole to fit on this thread. Then use a length of threaded rod with a stop screwed on the end and adjust this to whatever position you need inside the spindle.
P.S. Don't leave a couple of feet of threaded rod sticking out the end of the cap and turn the machine on....unless you like excitement.