Edge finders - cheap and cheerful.

[John Stevenson]

OK groupies cheap and cheerful edge finder, Mark 1, Patent pending .........TM.

For all you metrically impaired folk I'll work in inches.
Take a look in your scrap bin and sort out a sealed bearing with a OD of a nice round figure say 1". Then take a piece of silver steel or drill rod for our cousins that fits the bore of the bearing. This needs to be about 2" long. Fit the bearing with a dab of loctite and that's it, job done.

To use, chuck the drill rod shank up and start the spindle of the mill, about 200 to 600 rpm is OK, it's not critical.
Slowly bring the OD of the bearing into contact with the work, watching the bearing. As soon as the outer race makes the slightest contact with the work it will start to slow and run at about 1/2 speed. At this point raise the bearing clear of the work and you will be exactly 1/2 the bearing diameter away from the edge. This is why it's best to choose a nice figure like 1" or 3/4"
If you do have a crash and bend this - so what. Just fit a new shank.

John S.

[lynnl]

That falls under the heading WDITOT ('Why didn't I think of that?')

[bdarin]

Hey, man. That's too simple. This is the computer age....everything's supposed to be complicated, hard to figure out, and impossible to fix when it breaks. Like your car.

[Peter S]

A dowel works pretty good, ie hardened and ground type. Stick it in the chuck, coat it with marking blue, switch it on, when the blue goes, you're there...

[John Stevenson]

Peter S,
Only problem with a dowel is is they are short, stubby, and hard, read rigid.
If you have a crash they are more liable to do damage than a slender piece of soft drill rod.
I'd use one on a manual machine but not on a CNC

John S.