Hi Marv,
No ! there is no method to disconnect the leadscrew. I did make a spring loaded clasp for it but found that I couldn't overcome the slop in the slide without making it so tight that the spring wouldn't push the blade back fully. I gave up after that, other things became more interesting.
One idea that I did have, was to make a cam that rotated a short threaded piece against the leadscrew threads, a bit like a lathe half nut only much smaller but I never followed it up.
Just out of interest those bearings in that last picture are precision double race ones from the guts of old 3.5" hard disk drives. I dread to think how much they would have cost if I had to buy them.