There is none . Most pen caps , kit and brand name , use multi start threads , with triple start being the most popular , meaning that there are three sets of threads in one package . While triple start taps ands dies are available , they are special order and very expensive , I bought a single size that fits the El Grande size pens in a group buy a couple of years ago and the cost was around $200 for the set of one tap and one die .
You can use regular single start taps and dies to make caps and body threads but these type of threads require more turns to cap and uncap the pen and personally I don't like the look or feel of them (the threads are too big and feel very rough to the touch . HF has a great set of taps and dies for around $50 or so and gives you a good assortment of sizes to experiment with and you can make some nice pens with them .