The arbot bolt (104) passes through 106 (bearing) and 115 (spanner
nut). The nut (116) screws directly onto the threaded end of the
arbor bolt (104). From what I can see, the spanner nut simply holds
the bearings in-place, and the nut (116) keeps the arbor in-place
(from sliding side to side) inside the bearings, allthough the pulley
(110) also keeps the assembly locked in-place side to side. The
spanner nut (115) actually threads into the arbor bracket (114). So I
think all I need to do is tighten that nut (116). But that seems too
simple -- hard to believe that one nut is all there is to it. But
visually that seems to be the case. I cannot see the load spacers
(107 and 108) on either side.

I do get some saw marks -- that in my opinion should not be there. I
figured the arbor should have no play what-so-ever.