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.
Each H limit represents 0.0005 inches over basic pitch diameter. The best way to visualize the differences in screw thread classes of fit is shown on the bar graph in Figure 2. This example shows the pitch diameter limits for Â¼-28 UNF internal and external standard threads.Metric threads use a different system for pitch diameter tolerances. And, this system is a bit more complicated than that used for inch threads. The tolerance class consists of a tolerance grade and tolerance position.e will focus on the pitch diameter tolerances to keep it simple. Typically there will be a number and letter following the thread size to designate the class of fit. On inch sizes, the number 2 or 3 expresses the class of fit, and the letters âAâ or âBâ designate external or internal threads respectively.