Line boring

headstock boring
https://www.youtube.com/watch?v=zbeeMu4b9Hw In line boring and overlay welding on a blind hole, this technique is used to line bore a Lathe head stock.

https://www.youtube.com/watch?v=JyS26b-w4ic

https://www.youtube.com/watch?v=qfsUY6UVVgI

https://www.youtube.com/watch?v=3PvbCS8yJS4 aligning boring shaft

links
Lathe bearing design