Mounting a 4-Jaw Chuck On My Lathe (Video)

I had received a 4-Jaw chuck that was going to be scrapped a while ago, but suddenly became inspired to finally mount it on my lathe after watching this video.  Also the revelation that I actually had a right-angled screwdriver that could help me disassemble the original chuck mount made it possible.
I didn't really cover the process of building the adapter in the video so here are some more detailed photos:

I started with this scrap piece.  I had to use one of the lathes at school because mine couldn't hold this large of diameter.

 Then roughing the diameter for mounting onto my spindle.

First side of the adapter done.

Then indicating it in the mill to drill the mounting holes.  For those that have seen the 5-C collet closure post, this will look very familiar because it required a lot of the same steps.

In fact, I saved the same scrap piece of paper with the dimensions on it from 5 years ago!

Drilling the tap drill holes.

Tapping the 5/16-18 holes.

Then the holes for attaching the chuck were drilled and tapped.  This was a square hole pattern, and also conveniently, 5/16"-18 thread as well.

The chuck holes intersected with the round register on the reverse side, so I went in with an end mill to add a small relief.  This prevents the thread from mushing out and causing misalignment.

A picture of the 4-jaw chuck next to my 3-jaw chuck.  Awfully convenient that I found a chuck the perfect size.

All mounted up after the steps done in the video.

Facing a square piece of material.  This was the test piece I ended up keeping as a coaster.