do I take the reading just as the edge finder touches the part or should I back if off the part untill the light almost turns off, then take the reading?

also are these things the best way to edge find?

also if these things get pushed against the part too hard will they lose thier accuracy?, worried mine has gotten bent a bit.

thanks R

http://www.metalwebnews.com/howto/edge/edgefind.html

http://youtube.com/watch?v=f0od-cp_9dg&feature=related

Two tenths of a thousandth is pretty accurate.

good info thanks! is is needed to spin the electric edgefinder too? in the video he had the spindle on!! thanks. is electric less accurate?

If the edgefinder is running true, there would be no need to have the spindle on.

If you're worried about bending it, there are brands that the stylus rides on a spring and gives you some overtravel safety in X,Y,Z

I don't spin mine, to avoid marking the part... I was surprised to see it spinning in that video. Is that normal?

Laka, do you have a link for one of the spring-protected types? That sounds great.

Thanks,
Dave

Here's a tip:

Don't use an electronic edge finder. I've used two separate ones. The tip may flex away as a safety, but it never returned to the same spot. Try indicating the tip of the indicator. Does it run true? If not, mark the high spot. Now bump it lightly. Re-indicate it. Does it run the same as before? Never did for me. Maybe I bought the wrong ones, but that was my experience...

What if your collet (if that's what you're using) runs out? Touching off with the spindle off may provide an error of that magnitude, or none at all, depending on your spindle orientation. So you turn on the spindle. You have now a diameter of (the tip) plus any total indicated runout. So methinks .0002" is a stretch, unless you take all variables into account.

As far as accuracy for finding a edge I have always disliked edge finders. Spinning them too fast creates static electricity and makes them become magnetic or so the saying goes. Not to mention the last thing you want to do is use one on a block that is already magnetized (aluminum don't count lol). Also refrain from slapping them in a chuck...if your looking for trueness a precision collet holder would be your best bet. Oh and watch the burr on that edge! If your getting into close tolerance maybe a chair with high tolerance Interapid would suit your needs better as long as things are square... ha. Spinning a electronic finder is similar to continuously spinning a needle wiggler/ pointer... must be that same guy.

Go to travers.com and search this part number

#EEF-1 ELEC.EDGE FINDER

this is the one I've used before I went the probing route which is your best bet!

Fowler makes a great electronic edge finder,

They have a inexpensive model for about $20.00

http://www.use-enco.com/CGI/INSRIT?PMAKA=307-3436&PMPXNO=8137958&PARTPG=INLMK32

and a very good one for about $95.00

http://www.use-enco.com/CGI/INSRIT?PMAKA=326-1325&PMPXNO=12387605&PARTPG=INLMK32

Jeff...

Link to a spring-loaded edgefinder. We use this style daily. Never have any problems.

http://www.kbctools.com/usa/PDF/u0693.pdf

(It's the one on the bottom right of the page)