Tapered threads. They stuck.
I have drilled and sawed out pipe plugs. Then chase threads with a tap to clean it up if i nick it with the saw.carbide burr works too. Go slow and find the points of the threads.
I got home tonight and am now the proud owner of a Dd coffee club calendar, clearly I have no legacy or claim to being part of the cool kids club (yet!) but I got me one righteous Dd calendar!
On serious note it is very well done and will hang proudly.
Kind of like being well hung only different! Hah!