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One of the things I have always tried to do whether making internal threads on ACME, Butrus, Jacobs, API tapered, NC, NF, UNC, UNF UNEF, UNS, ETC, you get the picture is if I don't have a tap for the size and pitch, I will make the male thread first, hopefully out of a grade of material I can harden after processing. once I have the go no go thread made I grove it just like a tap and grind a cutting relief on the first couple of threads, in effect making a tap. If I already own the tap of the size in question then I do as you described, single pointing the thread to between 60 and 80% sometimes as much as 95% depending on the material being threaded IE stainless 4140 , stress proof, 4330,ETC, For bronze or cast iron maybe only 60% even when finishing off with the go no go tap gage
When making metric threads without a tap on either of my lathes since I do not have metric change over gears I try to get as near to 0% error pitch as possible then run a hardened bolt in and out a few times to finish off the thread almost any metric thread length less than 2xdia seems to work just fine long external metric threads are another thing entirely. but 1 of my lates has enough thread combinations to go from 4 TPI 228 TPI starting at 4 TPI advancing by 1/4 threads per inch through 5 TPI then by 1/2through 12 TPI from then on to 27 TPI in increments of 1 thread per inch eventually advancing by 2 threads and on to much larger increments. like 40 56 64 72 80 120 there are a few numbers in there I have probably left out so most of the more common metric threads from 1 to 2.5 mm I can come close
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