Tailstock die holder. By Skillful Man. 14:30 video:
https://www.youtube.com/watch?v=cxxBuwCiRa8
Related:
38 sets of plans for homemade tailstock modifications and accessories
Tailstock Depth Indicator by Christophe Mineau
Tailstock Die Holder by mr95gst
Tailstock Taper Turning Attachment by rossbotics
