Like I said before, a tap isn't necessary... but it really does help prevent cracking in printed parts.
We want the screws to fit nice and snug in the tiny hub.
And fairly loose in the arms that cradle the hub.
Turn the hub as you go to make sure that it moves free and smooth.
If it binds too much, you're going to make the servos work much harder than they need to.
We need to add mounting caps for the dowel and the eye plate... so don't assemble the other side of the u-joint just yet.