Of course the depth of the thread is at least as important as the OD.
It depends on the steel and the state of the die. I've got 8-off 1" 8TPI BSW dome nuts to make for the railway, and because the taps are in decent condition and the steel is quite good BDMS, I can do it if I cheat a few thou on drill size to give meself a bit less metal to shift. And it's lucky there's no particular time pressure.
But I can remember trying to die-cut some 1" BSW external threads on EN8 using chipped WD dies that might've gone through the desert with Montgomery. I ended up with a ricked neck and horrible galled threads.
I'd say if you've got good freecutting MS, 10 thou or a bit more undersize, a nice sharp die, a long-handled diestock, some Rocol or suchlike and you've had good coffee and an eggy breakfast, you might have a chance with 1 1/2" BSW.
But don't be doing it with difficult material, worn dies and wonky diestock at the dog-end of a rough day.
Edited By Mick B1 on 18/05/2020 20:22:48