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.
Tom's useful info: Pitch Conversions. Threads per inch, Pitch in inches, Pitch in mm. example 1/4-20 taps the. 20 signifies 20 threads per inch =.050 pitch ( 1 divided by 20 ) or if you are measuring in metric. it should be 1.27mm. Back to Top of Page. link to Thread Identification page.