Likely the biggest thing that most don't understand when it comes to folders of any sort, is the need for PRECISION size of pins/parts. The reason that most folding knife parts cost what they do, is because you are paying for the precision. For example, the K & S materials you mentioned are based on NOMINAL size....meaning that they are usually +/-.005 of the size they are listed. That doesn't sound like much, but with folders, we deal with such tight tolerances, it means the difference between a part working, and not.
When it comes to purchasing pin stock for folders, keep looking until you find ones listed a "precision", then check with the seller that whatever you are considering purchasing is indeed precision...... in other words, if you purchase 1/8" pin stock for folders..... it must consistently be .125"..... NO VARIANCE...... otherwise you'll drive yourself nuts, trying to figure out why the pin won't work as it should.
Something to think about, that may be helpful...... when we build or work on straight knives, we generally can get away with thinking and working within fractions of an inch. When it comes to building or working on folders, you have to train yourself to think and work in fractions of a thousandth. Some will find that silly.....until they actually start building or working on folders....then it becomes obvious.