My nephew, an expert machinist, pointed out that unless I created a landing of some sort on the motor shaft for the pulley's set screw to rest on, it's likely that the pulley and shaft would soon turn independently, once the saw was under load. Much to my surprise, a small sanding drum did a nice job of it. I had a pair of vise-grips clamped to the opposite end of the shaft and hanging straight down to keep it from turning. I ended up making the flat a bit bigger by hand filing, so I think I could have done it all that way if I hadn't had the sanding drum.

Note all the masking tape covering ventilation holes in the motor -- there are big magnets in there, and it's best to keep the iron filings out.