The maple was turned to about 3/4" thick and slightly concaved for good fit to the base. A #14 self tapping sheet metal screw 1 1/2" long was inserted into the center of the chuck. This is now a screw chuck.
Intermediate Woodturning Project
Table Lamp - page 2
Making the screw chuck and mounting the base
A 3/16" hole is drilled into the center of the base in preparation for the screw chuck.
Fasten the base piece to the screw chuck and rough it round.
Turn the base round and concave slightly what will become the bottom. Sand it to at least 220.
Make sure the 3/16" goes all the way through and flip the bottom section around on the screw chuck.
Turn the base to a pleasing shape, realizing that the top will need to trasition into the shaft of the lamp.