Having failed to correctly align this screw section with the end of this stepper motor shaft in a previous blog post, I thought some more about a better way to do it.
Then it hit me - I could use a drill press (or a milling machine) to do it.
1. UNPLUG the drill! No, seriously, really unplug it. Do it.
2. Open up the chuck and insert the motor shaft in there and gently tighten it. If you use a milling machine, lock the table in position with the locking screws.
3. Lower the spindle until the body of the motor is resting flat on the drill press table surface.
4. Secure the motor body to the table using gaffer tape or blu-tac or whatever you like, just to keep it motionless while you undo the chuck.
5. Open the chuck completely and raise the spindle again, leaving the motor fixed to the table surface. At this point the motor shaft is still concentric with the spindle.
6. Insert the worm screw section into the drill chuck and gently tighten. Do not damage the screw's thread.
7. Put a tiny amount of epoxy (I used two-part araldite) onto the end of the motor shaft. Don't get adhesive inside the stepper motor else you'll have a very unusual paperweight.
8. Move the spindle down until the screw just touches the end of the motor shaft. Do not press down on it.
9. Lock the spindle in place.
10. Walk away and wait for your epoxy to go off completely. I waited a whole 24 hours, because this wan't a time-sensitive part of the build.
11. when you're satisfied that the adhesive is set, carefully open the chuck and raise the spindle. Then liberate the motor from the table.
That's it! It does have the disadvantage of tying up the machine for a while but I can live with that given that this method would give very accurate alignment.
I've been watching a lot of metalworking videos on youtube lately and this idea came to me just now. It's amazing how versatile simple metalshop tools can turn out to be.