This 4 indenpendant jaws diam. 420 mm (16.1/2") chuck is a little headacke as it weighs around 65 kg (144 pounds)
The first practical work was a square key for a lathe chuck. Being used to a DRO on my larger lathe, I also added a digimeter to the VersaMil carriage so that I can read its height.
Milling the sliding slots on the home made die holders