how do you edge find

There's been a role reversal at my place...
Whenever "The Kid" is home, I watch him machine to learn. he edge found a
part (in 15 seconds!) by flicking the edgefinder to make it wobble and then turning the crank till it was on center.
I've always cranked till the finder "kicks" to one side. I don't have his accurate eye sight and feel to do it that way. My results weren't as repeatable ( I tried after he left) so I'm back to the "kick"
Karl
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On Tue, 22 Jul 2008 20:24:43 -0500, "Karl Townsend"

Greetings Karl, I also let it kick. But when it does I figure that the edge finder is .0005" past the edge. So with the digital readout I move the table 0994 when using the .200 dia. edge finder and call that zero. Always works for me. Eric
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I've got one of the lazer finders from Little Machine shop. It has a very fine focus lens. If you make the dot almost invisible then split the beam with about half on the work, it will get you within a gnats ass of the edge.
Bob Swinney
Bob Swinney
There's been a role reversal at my place...
Whenever "The Kid" is home, I watch him machine to learn. he edge found a part (in 15 seconds!) by flicking the edgefinder to make it wobble and then turning the crank till it was on center.
I've always cranked till the finder "kicks" to one side. I don't have his accurate eye sight and feel to do it that way. My results weren't as repeatable ( I tried after he left) so I'm back to the "kick"
Karl
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Karl Townsend wrote:

I use the method your son uses. It just seemed like the obvious way to me. So if you touch the work with a spinning edge finder it will kick to one side? I will try it and see how it goes.
Thanks, BobH
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The instructions that came with my edge finders say to use the kick. I hadn't heard or thought about that idea until I read the instructions and tried it.
I certainly feel like using the kick makes the edge finding more repeatable. But I do wonder about what the true position of the edge is when you use the kick method.
Since I don't own a mill and have only used my edge finders with the school's mill, (and the class is now over) I can't spend the time to experiment and try to answer that question. The idea of assuming it's 5/10,000 over suggested by the OP seems reasonable.
I guess to experiment, what I might do is machine a piece to an accurate width. Locate it with the edge finder, and then machine 1/1000 off opposite edges with an offset so I could mic the new widths relative to the old width, and relative to each new cut and see how the numbers worked out. That is, I would leave the piece so I could mic it from an old edge, to one new edge on one side, and from the other new edge to the opposite old edge, and then from new edge to new edge.
The goal of course is to find a way to use the edge finder so that these 1/1000 cuts would take an equal amount off of both edges after setting the location with the edge finder.
--
Curt Welch http://CurtWelch.Com /
snipped-for-privacy@kcwc.com http://NewsReader.Com /
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I go in with it wobbeling,
watch it center up
zero the DRO,
crank a bit more and watch it "jump" (I don't call it kick) sideways,
recheck the DRO and if it *ISN'T* plus .0005 or .001, I do it again...
FWIW an old timer told me to take it to the "jump" and call it zero (like you do).... go figure
I also find it works best at about 1000 rpm... "jumps" real fast then
--.- Dave

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wrote:

I do it your way, Karl. That's what they taught me back in the 50's, when I was an apprentice and I don't see any reason to change, as it has always produced satisfactory results for me.
Lewis.
*****
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I got shown another method at school on Tuesday - chuck up a dowel pin, say 10mm, and coat it with marking pen - bring work to spinning pin until you just see a faint line appear on the down as the job wipes it off. Then add 5mm (ie, 1/2 the pin diameter) and you will have your edge...then add 1/2 job diameter if you want the centre - zero your DRO - this was part of the setup for an indexing exercise..
Andrew VK3BFA.
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On Tue, 22 Jul 2008 20:24:43 -0500, "Karl Townsend"

I go for the kick. Watching the wobble require that one can see .001" or less of wobble, while the kick is considerably less subtle. The kick seems to be accurate and repeatable to .0005 or so, close enough for me. I usually check it once or twice to see that I get the same readings.
A good centerfinder (Brown & Sharpe) works considerably better than a Chinese knockoff for just a few bux more.
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On Tue, 22 Jul 2008 20:24:43 -0500, "Karl Townsend"

Last year at EASTEC I picked up a Hermann Schmidt edge finder. Very accurate and excelent repetition. Worth the extra $$$ for quailty!
You can rest assured that I do NOT let my students borrow it!!!
http://www.hermannschmidt.com /
Errol Groff
Instructor, Machine Tool Department H.H. Ellis Technical High School Danielson, CT
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I just had to jump in with a mildly off topic response: Yesterday I was showing a student how the edge finder did the 'jump' when it contacted the surface (and the usual discussion about the .0005" to .001" difference from the 'real' edge) when the jump went the wrong direction. !!@##@!!! I had been running it in reverse! cue to very red faced instructor.
Karl Townsend wrote:

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Was it a Bridgeport? - the ones at my college do that, when you go from H to L range, on one of them you need to reverse the motor.....I have to work it out each time.....why its done that way, no idea......
Andrew VK3BFA.
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snipped-for-privacy@hotmail.com wrote:

It's just the way the back gear train works. A lathe back gear inserts two reversals, so the spindle ends up going the same way. The Bridgeport uses a belt drive to turn the back gear, so engaging the gear only inserts one gear train reversal, so the spindle ends up running the other direction. You get used to it if you use it often.
Jon
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RoyJ wrote:

What's the diff? An edge finder is just about the only thing you'll ever put in a machine tool spindle that doesn't care which way it is turning.
Jon
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On Tue, 22 Jul 2008 20:24:43 -0500, "Karl Townsend"

I can't see why it would make any difference to the edge finder which way the spindle is turning. Other than if you are used to seeing it kick in one direction it would be disconcerting to have iti kick the opposite way.
As to which way the spindle turns in high or low range I tell my students at least a zillion time a year LOOK at the tool when you start the spindle. Then you will SEE which way it is going. Saves on end mills and drill points to know which way the tool (spindle) is turning.
Errol Groff
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It doesn't really make a difference whether the spindle is running cw or ccw, as the edge finder will still jump.. Just that if the edge you're 'finding' is the X- edge and you're running the spindle ccw it will jump toward you and is easier to see the jump, IMHO.. On Y edges the jump is sideways so easy to see in either direction.. One of my edge finders [I think from SPI] has a very small flat ground on the . 200 diameter so it gives you an audible as well as a visual indication of the jump.. Just my $0.27 worth..
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Karl Townsend wrote:

I don't know how well the technique would work for you guys who don't work with mushy stuff, but I made a gizmo that allows me to locate a corner of a workpiece (and either zero all three axes or just report the x, y, and z coordinates of the corner.
There're photos at http://www.iedu.com/DeSoto/SuperZero/ and a detailed description at http://www.iedu.com/DeSoto/SuperZero/ReadMe.html
I think I know how to make the little bugger work on "real" machinery, but don't have any to play with. :-)
Anyhoo, I thought it might spark a few ideas...
--
Morris Dovey
DeSoto Solar
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