Thanks to everyone kind enough to help me with this!
Here is a (hopefully)better photo of the screw and also a somewhat blurry
one showing the penetration of the screw into the bushing where it stops at
the motor shaft flat. I hand tightened it on the motor shaft and slid it off
to show this.

Here's the latest link: http://www.waycoolgear.com/ebay/screw_in_bushing.jpg

When I screw it in more (with the motor shaft removed), it seems to bite in
and hold just fine without stripping at all.

I'll try to get even better photos if you guys think it will help more. Just
let me know exactly what you need to be of assistance.

Thanks !