Personally, I think AICC should be punted over the goal post of so long compliance standards. and some vendors like to offer multiple choices, and yes AICC does different things, but so does driving a moped and I rarely seen people cruising down the interstate on one (unless you live in LA).
Part One: How to Measure Thread Size. 1  In general, the thread should match the fabric in size and weight. For heavier, thicker fabrics, use heavier thread. 2  Heavier threads create more visible stitches. 3  V-69 is the heaviest size recommended for sewing machines. 4  Heavier threads are stronger.
The Needle Gauge is the fastest way to find out which size those circulars are. The tension gauge has a 5x5cm square (2x2 inches sq.) window for measuring the numbers of rows and stitches in. Like the needles & hooks, they are made in Germany by Addi.