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.
This is the number of complete threads occurring in one inch of threaded length. Metric thread pitch is. designated as the distance between threads (pitch) in millimeters. On an internal thread, the minor diameter occurs at the crests and the major diameter occurs at. the roots. On an external thread, the major diameter is at the thread crests, and the minor diameter. is at the thread roots. The flank angle is the angle between a flank and the. perpendicular thread axis.