I don't recall if I took the fan off when I cleaned and replaced seals on mine or not, or if there was thread locker.
From the Parts Diagram and Parts List, it appears to be a 1/4-20 x 1" hex head bolt. No mention of left or right hand thread. Before I would call it junk I would definitely try drilling it out, even if you have to go up one size for a new tapped hole, or fill hole with steel rod or bolt and JB Weld and drill and tap a new 1/4-20 hole.
Shopsmith DC3300 dust_collector02-300dpi.pdf
Shopsmith DC3300 dust_collector03.pdf