http://www.3-a.org/standards/standards.htm
You can download standard if you don't have them.
We consider the thread "ACME" when we talk in general. The manufacturers of fittings would the exact dimensions.
Often you can get and adapter made and not have to cut the thread yourself...
Culinary steam for introduction into MILK products is well defined by 3A standards and the PMO (Pasteurized Milk Ordinance).
http://www.3-a.org/ see 609-02
http://www.wa.gov/agr/FoodAnimal/Dairy/LawsRules/1999PasteurizedMilkOrdinance.pdf (just one of many sites)
I too am looking for...