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? LOLAnyway, 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.