Best edge finder?

[Rickabilly]

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So this is the Ebay picture from CTC so should be the same as Tom's and looks a lot like mine, they are so cheap that we used to keep one in a holder on each machine when I had employees, when I first started using them they were over $100 Au and even at that they were so handy that I felt it was essential on any CNC.

simply mount it in the spindle in a collet of some type and bring the ball up to the side of the work piece and stop when you first hear the buzzer and see the light, even when a truck and three other machines were running I could still hear the buzzer and my ears aren't great. then either set to -5mm or raise the z and wind the dials a further 5mm observe that the centre of the ball is directly over the edge and set to zero and you are done,
When finding centre of horizontal shaft you don't need to be on the vertical centreline, rather just close by eye and maintain your z when checking both sides then split the difference.

When finding centre of a vertical round pin or boss first roughly guess set centre in x and then locate centre in Y, once you have centre in Y touch off and find accurate centre in x.

I would use the LED finder and then finish with a DTI at the beginning but after six months of checking it was always within a thou or two so now I only check if it is absolutely required.

Another handy edge finder is the Laser one I have, it is pretty much a really fine laser pointer that has a shaft for spindle mounting and some centering screws for adjustment, you simply mount it in the spindle, turn it on, run the spindle, and bring it up to the edge, when you first see the light on the side of the work stop and zero the dials then continue travel until the spot is on top of the job and the lightest bit is still running down the side (just a shadow of the beam light, not that you can have a shadow of light, but you would know what I mean when you see it) read the dial, halve it and you have edge. They advertise it by saying just see the light and you're on centre and it's close but not quite, I prefer to split the beam. I have attached a picture below. It is really handy if you are setting up to parts that are complex in Z as you just leave the Z up to 12" away and the light beam does all of the "up and down work" for you, it's also great for centering drills in centre punch marks
   

Regards
Rick