# Used my electronic edge finder first time today---



## Brian Rupnow (Jul 5, 2008)

And darn, it works just like the books said it would!!! Remember---I am a veritable "new guy" when it comes to using a mill. I knew the theory of how an edge finder works, but had never used one before. Any milling I have done so far was up to scribed lines, and any holes I drilled using the mill were layed out and lightly center punched first. This time I had to put a cross hole thru the flywheel for my model steam angine for a split pin to hold it to the shaft. Of course, a round part like that is kind of a pig to lay out, so I thought "Ahah---A perfect time to try out the center/edge finder!!" I measured the flywheel thickness, divided by 2, and added 0.100 (half diameter of the edge finder probe). I set the edge finder up in the mill chuck, advanced the side to side table movement untill the edge finder contacted the part and the light in the edge finder came on. Then I lifted the head out of the way, set the table dial to zero, and advanced the table by the amount I had calculated using the feed dials on the table. Then I repeated the process in the other plane. Hot Dog!!!! It worked perfect. Then I locked both slides in place and drilled through the flywheel and crankshaft end together, and the hole was exactly where I wanted it to be. I love it every time I get to use something new, and it works exactly as I thought it should, from reading about it.---Brian


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## BobWarfield (Jul 5, 2008)

aren't gadgets great?

Ihavs a set of starrett mechanical edgefinders, but emco has the electronic ones on sale so I ordered one.

Cheers,

BW


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## Jasonb (Jul 5, 2008)

I use mine a lot now rather than marking out, particularly easy with digital readouts to take out any error due to backlash.

Just be careful not to wind it into the work too far and bend the end out of truth :-[

Jason


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## mklotz (Jul 5, 2008)

Brian,

It's my understanding (subject to correction) that there are two kinds. The simpler ones are nothing more than a (electical) continuity checker. The circuit is completed through the workpiece, table, column, bearings, spindle, etc..

The more complex ones have some sort of internal "tickler" mechanism which, when disturbed by the contact with the workpiece, closes a circuit internal to the edge finder and thus does not depend on electrical conductivity through the machine.

I've always wondered if the former type - the one that relies on conductivity through the machine - would have a problem with an oily workpiece or, for that matter, a non-conductive workpiece.

Could you check this for me? Try finding an edge on a piece of plastic and see how it works.


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## Powder keg (Jul 5, 2008)

Marv, The electronic edge finders have to be able to make a connection. So your part has to conduct electricity. At work some of the parts are heavy metal plate and the scale on them doesn't conduct electricity. It has to be ground off to get a reading. 

W


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## BobWarfield (Jul 5, 2008)

If you prefer a "tickler", there are quite a few articles on how to make a probe such as the CNC'ers use. There's no reason you couldn't use such a gizmo as an edgefinder. 

Here is one such article:

http://www.indoor.flyer.co.uk/probe.htm

Somewhere I have seen a quarter digitized with one of these homemade probes and the detail was amazing, so they're quite sensitive.

Cheers,

BW


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## Bogstandard (Jul 5, 2008)

I did a post a bit back about the most useless tools.
The winner was a magnetic optical centre punch, that, unless used in a clean room environment, was totally useless because it sucked up ferrous chips from everywhere and made it unusable.
This one came a very close second, and here is a quote from the article.



> Here is another one I found, covered in dust at the back of the shelf. I will own up to purchasing this piece of useless junk. Looked good at the time.
> 
> 
> 
> ...



It now has a tiny bit of cosmetic rust, I have put new batteries in it (a waste of batteries as far as I am concerned). New pic below.

If anyone in the UK can use this, you can have it for the postage costs.
If no takers, I will try to get Ralph to take it away on one of his visits. Maybe he can bling it up and make an engine with lights out of it.

John


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## Brian Rupnow (Jul 5, 2008)

To all the Nay-sayers---My edge finder is the cheap one that depends on continuity of current through the workpeice. I chose it because any conventional edge finders that I have seen depend on the spindle being under power and revolving to use them. In my quest for working safely, and keeping the ten digits that I've had for 62 years now, I thought it might be a tad safer if I could do my edge finding with the spindle not turning. Yes, if I want to mill something non conductive, I will have to find another means of edge finding. If the part is oily, I will wipe it off. If the part is rusty---well, maybe I'll just be out of luck.


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## Bogstandard (Jul 5, 2008)

Brian,

I wasn't getting on at your choice, it was about MY choice, the morse taper version is a PITA to work with, for the reasons I described, in fact almost impossible on a round column mill/drill. I am sure you wouldn't have the same problems as I did with a straight shank one, or with a dovetailed column on the mill.

BTW, it did work very well. It was the problems afterwards that caused me to reject it.

To get over the non conductive issue, set up from a datum face (vice jaws and backstop) using say a parallel, then just swap it out for the part you are machining.

John


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## shred (Jul 5, 2008)

I have a little LED height presetter that works off continuity (I suspect that probably gives a more reliable result overall, there being no critical moving parts). Since the table on my Taig CNC mill is anodized aluminum that doesn't conduct well, I rubber-banded on a fly-lead with a clip. Clip that to the tool bit and it lights up every time, even on wood or plastic. While not so good as an edgefinder, it can be pressed into that service for that by using it horizontally.


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## BobWarfield (Jul 5, 2008)

Bog, I believe I wouldn've made a sleeve or just bloody well turned that taper off you edgefinder!

BW


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## Bogstandard (Jul 5, 2008)

Bob,
Already thought of that. To put it into a sleeve would make it too large to hold.
I thought of turning the taper down but came up with two problems. To turn it down enough I would have broken into the battery compartment, also, how accurate would it be after I had finished turning, as I couldn't mount it into a collet, as the ball wouldn't pass thru the hole for the correct size to hold the plain shank.
Really not worth the effort and time to solve the problem.

John


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## Philjoe5 (Jul 5, 2008)

Brian,
You sound as pleased with your electronic edge finder as I was when I first began using it. A couple of points have been raised that are useful for improving its accuracy. I have found that if the contact point on the workpiece has Dychem on it or other marking fluid it may take an extra 0.002" or so to make the led's light up. A light buff with #1200 or acetone will improve that. To get the finest readings, take a reading, rotate the spindle 180 degrees, take another reading and take the average. I've used mine for almost 2 years and couldn't (wouldn't, shouldn't) be without it.

Cheers,
Phil


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