Some lampholders have threaded bases to accept threaded tubing.
What thread is this? From memory I think there may be 2 different kinds.
I am trying to convert 2 big old porcelain vases into lamps.
The vases are each about 650mm tall and contain suitable drillings.
Any ideas please on (a) what it's called and (b) where can I get the stuff.

Many thanks

Nick.