Ok... I did it. I ordered the (expertly) machined spindle from eBay... to convert my 3" Cutoff Tool... into a 1/2"x18" Belt Sander.
The included instructions are well written. It is actually fairly easy to switch back and forth betwix cutoff and sander.
My Astro P sander needs a 4mm hex to remove the "works" from the air tool. Zero issues... just remember to remove the sanding belt first.
Removing the bits from the 3" cutoff was pretty simple... The instructions mention a "shim washer" that I did not have... Pictured here are the items removed and will remain in a box while the tool is setup for sanding. The FOUR T8 screws are reused with both setups.
Including the time it took me to walk to my toolbox 3 times for the following:
1. 3/16 hex T Wrench (to remove the cutoff wheel)
2. T8 Driver (to remove the 4 screws holding on the guard on the cutoff)
3. 4mm hex (to remove the works from the Astro P air tool)
The modification took all of 2 minutes. FYI A T8 bit is included with the kit on eBay.