i am not smart enough to do the finger spin test, so i made a simple spin tester. a 2x4 as long as the arrows will handle- with two scrap pieces of ply on the ends, with a deep(1" at least) V notch cut in each onei have some parallel lines drawn on the 2x4 running the length of the 2x4, about 1/4" apart.
so i lay the arrow in the notches, turn it slowly by hand keep my head real steady- sight over the arrow, and line it up with one of the parallel lines, and as i turn it i can see any deviance away from that line, or if it obliterates the line as it revolves, whip it off- straighten with chosen method and continue.
make sure your center line runs from deepest part of the V on one side to the deepest part of the v on the other.
i also use this to check my broadheads- sight the point of the b/h with a small spot on the work bench , and see if it deviates as you rotate the shaft.- keeping your head dead still!
have also seen them built with two large nails pounded in on either end forming an X- so it creates the notch's.
i certainly respect those guys who take a shaft, balance it on a finger tip, and use a deft flick of the fingers to spin it. just not for me i guess!