There are lots of variations in threading, I always use threading tools with the laydown triangular inserts. For internal threading I have the choice of normal right handed bars and left handed. The lefthanded are useful as they cut right hand threads away from the chuck with the spindle reversed. The last thread I produced was an Atlas 1 1/2 X 8 chuck backplate, which is similar to a Boxford one. There is a difference in the register and the threads are 60 degrees. I cut that away from the chuck which is easier as there is plenty of time to stop.
The more practice you get in, the easier and more enjoyable it gets. As already recommended, plastic is excellent as its very forgiving of mistakes.