Nice work mate. I like good home made anvils.
Another method for a hardy hole with the gear you have would be drill the hole as you have, thenweld 4 pieces of f/b corner to corner using the form of your hardy tool as a mandrel, pit it in a lathe and machine the o/d round to about 5 thou interferance and prep one end, then tap it in and fully weld the top.
As i said great job.