A very good video, but like many items I'd add that edge finders of this type have a direct relationship with there accuracy and exactly how well they repeat that kick off point to how well there heat treated, ground for concentricity, spring pressure, lapping finish of the end faces and even how clean there kept as well as the amount and type of lubrication used. My first edge finder was a cheap and poorly made one. Since it wasn't repeatable I no longer have it for testing purposes against the better equipment I now have. But I doubt it was capable of repeating within .003" at best. All edge finders of this type certainly aren't equal in there performance. It's very likely a poorly made one could be improved by machine lapping those end faces with a mill to improve the surface finish. It's still far better to start with something that's known to be well made like your Starrett. Any of the cheaper one's I've looked at over the years simply aren't made well enough to fully trust the exact point where that kick off happens every single time. A mill with a dro or even the ground gauge pin isn't an absolute necessity to run this test. An indicator and accurately measured but common 1"2"3" or 20,40,60 mm block most of us would have could also be used. If better accuracy is needed then centering stock directly under the spindle C/L can also be done to far higher levels of accuracy and to easily within a 10th or two simply by using a 10ths indicator swung by hand in the spindle and splitting the dimension in half. There's multiple and various methods that can be used, it just depends on the tools available and the accuracy required. A bit off topic to this video, but I have an old book first written in the early 1900's showing jig boring and finish grinding master gauges that were drilled, bored and internally ground to well under 10ths positional and size accuracy using a shop made dti and hardened and ground tool maker buttons, a very good micrometer and hand tapping the part into position on a lathes face plate long before jig borers and grinders were invented. I doubt I could duplicate what they were doing daily over a hundred years ago even with some better and much more expensive equipment than they had.

I've watched videos where the presenter pointed out that if you use an edge finder at too high an RPM, the eccentricity can throw the 0.200-inch end off of the tool, damaging the internal spring. I don't know how fast that is, but your speeds (RPMs) are fine. I keep looking for videos showing how to properly use the pointed end of edge/center finders though.

ON THE MAIN PICUTRE U SHOWED ANOTHRE TOOLS :THAT'S NOT THE ONE ON THIS TUTORIAL. i LEFT A NEGATIVE FEEDBACK !

where is the starret 827b?!?!?!?!?!? I'm trying to find the center of a hole.