API BOX THREADS

[mrgene71]

I am curious as to why the API thread charts do not show the large thd diameter for box thds at the face as they do for the pin threads. They show the box counterbore diameter - which is fine - but is not what is needed for determining precise thread diameters.
Or is there a formula to derive those dimensions, knowing the pin diameters?
Thanks for your assistance!

 

[MechyMarco]

API spec 7-2 has everything you need. You can find older free copies online.