To The Curious:
I bought one of the following edge finders years ago. Never really used it, since (like all the LED edge finders I have), it's not nearly as accurate as a normal edge finder, especially being as it's spring loaded.
Now I was setting up the 3D profiling operation on the following part last week. Picture resolution isn't so hot, I need better lighting, or maybe a new digital camera. It never did work very well for small parts.
Picture the 1/4" wide "tang" with the 5/8" bored hole in it being held in a vise with the 10 degree flat bottom (before profiling), sitting kind of like in the second picture. I wanted to find the center of the
10 degree angle in relation to the center of the "tang". So what I did was edge find the back vise jaw, move out half the distance of the 1/4" "tang" or .125", then put my X,Y,Z spring loaded edge finder in a holder, moved out half the diameter of the tip (.100) then brought it down until the edge touched the angled surface of my part and the LED's lit up. Recorded the Z value in the control, moved the edge finder to the surface of the back vise jaw and brought it down and touched it(LED's lit up. Wrote down the Z value, subtracted the two readings, then made up a Jo block stack at that dimension, and set my tools off of the Jo block stack. Was that clear as mud? LOL
Anyway, my point being, that that was the first time I actually thought of a use for that spring loaded edge finder. I didn't even think the batteries would still be good after all this time. Just sharing a little setup tid-bit that might prove useful to someone in the future.