# I was taught a new way to use an edgefinder today.  What are your thoughts?



## 9t8z28 (Oct 11, 2018)

Today was my first day on a new job.   The guy training me asked me to find the edge of the part so I pop in the edgefinder and crank up the spindle to 1K rpm.  I then flicked it with my finger to get it running off center, move it into the part until it runs true and then just when it kicks out I know I am on the edge of the part plus half the diameter of the tip.  In this case its a .2” diameter tip so I have to advance .1”.   This is the way I’ve done it a million times and I’ve even checked the accuracy of my edgefinders with my DRO and a DTI.   Anyway, The guy training me tells me I am doing it wrong and tells me to get out of the way so he can show me how its done.  His way of doing it is exactly like I described above but after the tip kicks out on the side of the part he reverses the table until the edgefinder runs true.  
 I was at a complete loss of words.   Being my first day on the job, I didn’t want to **** the guy training me off.  
 I did ask him what kind of edgefinder it was and he said it was a normal edgefinder.   I had a good look at it and it is identical to my Mitutoyo 050101 and starrett 827A which are both a 3/8” body with a .2” tip.  
 What are your thoughts ?   Is there some kind of a new edgefinder that I’m on unaware of ?


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## plunger (Oct 11, 2018)

I do it your way. Which is right?


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## 4ssss (Oct 11, 2018)

plunger said:


> I do it your way. Which is right?



X2


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## benmychree (Oct 11, 2018)

Your way is about the way that I have always done it, but I, advance very slowly until there is no "air gap" to be seen, with back lighting, so I guess that I am somewhere in between the two of you, it is possible to go a little past the zero point doing it the exact way you describe; someone years ago also suggested that grinding a small flat on the .200 dia. makes it all the more sensitive --- it works!


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## T Bredehoft (Oct 11, 2018)

I advance the part until it stops  wobbling then back it up until it just starts. I find (for me) it is  easier to see the beginning of the wobble as apposed to see the end of it.


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## 9t8z28 (Oct 11, 2018)

Have you ever tested this message to see how accurate it is ?  





T Bredehoft said:


> I advance the part until it stops  wobbling then back it up until it just starts. I find (for me) it is  easier to see the beginning of the wobble as apposed to see the end of it.


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## dulltool17 (Oct 11, 2018)

T Bredehoft said:


> I advance the part until it stops  wobbling then back it up until it just starts. I find (for me) it is  easier to see the beginning of the wobble as apposed to see the end of it.



..which is as I was taught, many years ago...


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## Technical Ted (Oct 11, 2018)

9t8z28 said:


> Today was my first day on a new job.   The guy training me asked me to find the edge of the part so I pop in the edgefinder and crank up the spindle to 1K rpm.  I then flicked it with my finger to get it running off center, move it into the part until it runs true and then just when it kicks out I know I am on the edge of the part plus half the diameter of the tip.  In this case its a .2” diameter tip so I have to advance .1”.   This is the way I’ve done it a million times and I’ve even checked the accuracy of my edgefinders with my DRO and a DTI.   Anyway, The guy training me tells me I am doing it wrong and tells me to get out of the way so he can show me how its done.  His way of doing it is exactly like I described above but after the tip kicks out on the side of the part he reverses the table until the edgefinder runs true.
> I was at a complete loss of words.   Being my first day on the job, I didn’t want to **** the guy training me off.
> I did ask him what kind of edgefinder it was and he said it was a normal edgefinder.   I had a good look at it and it is identical to my Mitutoyo 050101 and starrett 827A which are both a 3/8” body with a .2” tip.
> What are your thoughts ?   Is there some kind of a new edgefinder that I’m on unaware of ?



I was taught the same way as you and I've always done it that way and I've never really given it much thought; until reading your post...

I'm thinking that the person training you feels that for an edge finder to run off you must actually be a little past the edge. If not, in theory anyways, seems like the edge finder would be running true when just first touching and would have to be past the edge for the finder to move out and run down the edge of the work piece. He probably has a point.

But, for my use anyways, I use an edge finder to get me close i.e. within a thousandths or two of an edge and if I have a critical dimension I want to hold I would check it by some other means than just trusting and edge finder and then dialing off the distance (especially without a DRO).

So, old habits die hard so I imagine I'll continue to do it the same way.

Interesting topic!
Ted


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## MrWhoopee (Oct 11, 2018)

Run the edge finder up until it just kicks sideways, set the dial on the mill to 100. Taught that way in school, confirmed by my first boss. I've never seen it done any other way.

Edit: I do back off after setting the dial and slowly crank up again to double check the setting.


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## P. Waller (Oct 11, 2018)

Welcome to the world of working in machine shops, many people have different methods of doing the same thing, you will find this to be true in short order I suspect. 
Do it this persons way until they stop watching you at all times then use the method that you are accustomed to, as long as the parts are accepted over and over no one will care.

I do exactly what your trainer does by habit, not because it is better but for the simple reason that I have been doing it that way for 30 years of working full time in machine shops.
The only right way to do something is the way that works.


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## MrWhoopee (Oct 11, 2018)

Just found this video by Tormach. It says that the difference between the edge finder running true and kicked offset is .0005. If that makes a difference, you shouldn't be using a mill or an edge finder.


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## 4ssss (Oct 11, 2018)

MrWhoopee said:


> Run the edge finder up until it just kicks sideways, set the dial on the mill to 100. Taught that way in school, confirmed by my first boss. I've never seen it done any other way.
> 
> Edit: I do back off after setting the dial and slowly crank up again to double check the setting.



X2


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## Holescreek (Oct 11, 2018)

He's wrong. How does he know when the table is no longer touching the edge finder?  It will continue to run true after it is no longer touching the part.


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## P. Waller (Oct 11, 2018)

Holescreek said:


> He's wrong. How does he know when the table is no longer touching the edge finder?  It will continue to run true after it is no longer touching the part.


This makes me laugh out loud, keep up the good work as I enjoy such fixed right/wrong conversations.


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## RJSakowski (Oct 11, 2018)

The edge finder has been my weapon of choice in finding an edge for more than thirty years.   I usually make three approaches, the first rather quickly to get a rough idea of where the edge is and then advancing about .0001" every 1/2 second in the last 1 to 2 thousandths, repeating the procedure until I can locate an edge to .0001".

Approaching too rapidly will give a false position, either due to overshoot or if there is a small amount of wobble, kicking out prematurely.  It has been my experience that once the edge finder kicks out, you have to back away by several thousandths before the edge finder settles back to a stable mode.  

I routinely use my finger nail to recenter the edge finder after backing out about a thousandth as this reduces the amount of  travel for the next approach.  If I don't use my fingernail to recenter the edge finder, I have to back it out about 6 thousandths before it resets, at which point, there is a clear air gap between the edge finder and the work.


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## P. Waller (Oct 11, 2018)

RJSakowski said:


> repeating the procedure until I can locate an edge to .0001".



That is beautiful in every possible way.


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## RJSakowski (Oct 11, 2018)

Holescreek said:


> He's wrong. How does he know when the table is no longer touching the edge finder?  It will continue to run true after it is no longer touching the part.


He is saying that the difference between the centered edge finder and being kicked out is .0005", not going from offset to centered again. 

The edge finder of this type was patented by Robert Beatty in 1948. (US Pat. 2451904) Among his claims was that when an edge is contacted by the centered finder, the additional travel to the point where the tip is displaced  is never more than .0002".  Starrett also makes this claim for their product.


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## Holescreek (Oct 11, 2018)

Like everyone else, my Bridgeports were bought late in their lives and came with some "slop" in the screws.  I have a DRO with glass scales to take the guess work out of everything I do.  I use Fisher edge finders (not the ones that click) just about every time I set up a new part, be it picking up an edge on finding the mid point between the jaws of a part in the vise.  I set the DRO when the edge finder kicks out, then I back off and do it again. 99.90% of the time it kicks out within .0002" of zero. I do the same thing when finding the mid point, I touch each jaw and look at the number on the DRO. They match the same percentage of the time.  If I need real precision I'll pick up the edge with an indicator.
I learned long ago to recheck the positions before I cut metal, even if the location isn't that important. When I screw up, I screw up big time.


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## RJSakowski (Oct 12, 2018)

The great thing about an edge finder is that it is insensitive to runout. The tip centers on the spindle axis.  Electronic edge finders, probes and Haimer tasters all have to be zeroed to the spindle axis to read accurately.  As such, the orientation of the device in the spindle has to be strictly observed in order to maintain alignment.

Finding the midpoint with an edgefinder and DRO is particularly satisfying as I find one edge, zero the DRO (don't worry about compensating for the edge finder diameter) and find the opposite edge.  Then I hit [1/2] on my Grizzly DRO or enter "/2" and [ENTER] on my Tormach PathPilot display.  Zero is set at the center of my part.  Sweet!


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## Holescreek (Oct 12, 2018)

9t8z28 said:


> he guy training me tells me I am doing it wrong and tells me to get out of the way so he can show me how its done.



Here's why he's very wrong:

Lets ignore DRO's altogether. I never saw one on a Bridgeport until about 16 years ago.  A skilled operator will snug the table lock slightly when approaching zero to remove table slop and keep from overshooting a number.  They will also approach a dimension by turning the handle in one direction only to keep the lead screw on one side of the nut. If they overshoot the number they'll back off a full revolution and re-approach to remove all backlash. Having the lock snugged also allows some tension between the interacting surfaces.

Backlash on a Bridgeport (dead space between the lead screw and the Bronze nut) is typically set around .025".  If you change directions after your edgefinder kicks out, far enough to draw it back concentric you've not only removed all tension you set finding the edge, you're now on the wrong side of the nut (if you're lucky) and will need to use that same direction on you handle when moving to the next position.  More than likely you're actually lost somewhere in the backlash.

So nothing ever changes.  The dude is doing the Alpha Dog routine. Watch for wet spots in the corners of the shop. I chuckled about this on the long drive home tonight.


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## vtcnc (Oct 12, 2018)

Morning everyone! Please keep the conversation focused on the merits of the ideas and make sure we don’t drift into what could be misinterpreted as personal or ad hominem attacks on such a trivial life matter.

I think somebody said that at the end of the day, if the part is good, then there you go what’s the big deal?

I’d like to hear from members which method is faster, more repeatable, etc., without hearing that the other side is wrong - because they may be achieving the same accuracy but with more aggravation, more effort, more rpm, more hand wheel work , more math , etc.


Sent from my iPhone using Tapatalk


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## Cadillac (Oct 12, 2018)

Holescreek nailed it. Backlash would be your enemy attempting to return. I have a dro and really don’t worry about backlash except for these exact reasons.


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## 9t8z28 (Oct 12, 2018)

I am going to test the different methods this weekend and see what I come up with.


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## Dabbler (Oct 12, 2018)

How I was taught by a tool and die maker, is what is 9t8z28 tried first, except that he taught me to zero the DRO after the first attempt, and then repeat, always 2 tries.  If they don't agree, you have to repeat until you get the same measurement.  He demonstrated to me getting to withing one tenth reliably, many times in a row, with a very sloppy lead screw (just before he rebuilt the nut).  

with my offshore edge detectors, I am getting within 2 tenths every time, wo it is what I do...


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## gmcken (Oct 12, 2018)

I find the edge just as Dabbler suggests.  Zeroing the dro after the first touch off with edge finder and checking until I get repeatable readings.  Good discussion by members


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## dlane (Oct 12, 2018)

Cigarette rolling paper works for me, I have an edge finders but the papers are quicker.


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## RobertHaas (Oct 12, 2018)

Pre DRO I learned the move in slow to the kick. set the dial to half the Dia. of the edge finder then repeat to check work. It's funny but I make a habbit of doing things analog (or mechanical) then check my work with the DRO and feel so proud of myself when I hit it within a thou. or 2


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## Bob Korves (Oct 12, 2018)

I don't like to leave the cylinder rubbing on the work for long, figuring that will cause wear in and on the edge finder.  I go in once fairly quickly, then once slower, backing out immediately after seeing the number.  On something more fussy I go more slowly, and had most of RJ's excellent and eloquent post figured out, but use it rarely when I am trying really hard to get it right.


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## RJSakowski (Oct 12, 2018)

I would suggest that anyone concerned about of their edge finding method run an R &R test.

Repeatability: make multiple approaches to the edge and note the position with a tenths reading DRO, dial indicator, or test indicator.

Accuracy: find the opposite edges of a reference block, noting the difference in position with a tenths reading DRO.  Measure the reference block with a known good micrometer and compare.  This test would be more difficult without a DRO as position would depend on the accuracy of the lead screw, the ability to accurately read the dial to a tenth of a thousandth, and would have to take backlash in the lead screw into account.

I ran an R & R study this morning using my mill.  I mounted a 1-2-3 block on the table and swept the 3" face to verify that is was parallel to the y axis within .0005"  I zeroed the DRO in both y and z to ensure that I could return to those settings.  I then ran the edge finder to the left side of the block and zeroed the x axis.  I was able to return to the exact same reading on multiple approaches.  Readability to .0002" (the resolution of the DRO) confirmed.

Next, I lifted the edge finder to clear the block and approached the opposite side.  I approached multiple times, again verifying repeatability.  My reading was 2.4998".  Subtracting the .5" edge finder tip diameter., the distance across the block was 1.9998".  Finally, I measured the the 1-2-3 block at the contact point at 2.0000" with two different micrometers.   This amounted to a difference of .0002" or .0001" per side.  The Accuracy confirmed.

In my experience, several considerations are in order when using an edge finder. The edge finder contact surface and the surface of the edge being found should be clean and  smooth.  An oil or coolant coating will will create a film which will create drag on the edge finder tip and cause a premature jump.  I use a contact length of about 1/8" rather than exposing the entire tip surface.  When center finding using opposite edges, I make sure to use the same contact length.  I use around 700 - 800 rpm for spindle speed.  I also use a very light coat of oil between the tip and the shank of the edge finder.  I apply a droplet of oil to one surface and wipe it off, removing most of the oil.  I find the this gives more consistent jumps.  Erratic movement of the tip is a good indicator of the need for lubrication.  I set the preload on the spring at about 2 lbs. n My edge finder of choice (I have  two full sets of them) is a 1/2" one that I bought from Enco or Travers maybe thirty five years ago.  I prefer the 1/2" to the .200";  I think that it gives a crisper jump.  The larger radius means that less drag force will be required to make the jump.


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## RJSakowski (Oct 12, 2018)

Bob Korves said:


> I don't like to leave the cylinder rubbing on the work for long, figuring that will cause wear in and on the edge finder.  I go in once fairly quickly, then once slower, backing out immediately after seeing the number.  On something more fussy I go more slowly, and had most of RJ's excellent and eloquent post figured out, but use it rarely when I am trying really hard to get it right.


The one fault that I have with the edge finder is the mark that it makes on softer materials.  There is the possibility of creating a slight indentation on materials like plastic and I will also try to back off as quickly as I can.  As far as wear of the tip goes, I can't measure any after 35 years of use.


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## higgite (Oct 12, 2018)

I have 2 edge finders. One is a Fisher and one is a cheap, generic no name. Both have 3/8” barrels and .20” probes. Just for grins, I experimented a little with both this morning.

The difference between the Fisher and the generic when using the conventional method to find the edge was ~.0005” (5/10ths).

Then I compared the conventional edge finding method to 9t8z28’s trainer’s method with both finders. With the Fisher, the difference was ~.0006” (yes, that’s 6/10ths). But with the generic, the difference was a whopping .008” (yes, that’s 8/1000ths). The interface between the barrel and the probe of the Fisher is noticeably smoother than that of the generic, which I suspect explains the larger spread between methods with the generic finder. The interfaces of both finders were lightly oiled.

Measurements were taken with a Mitutoyo dial test indicator with .0005” scale increments and the edge being found was the fixed jaw of a screwless vice.

Now back to our regular programming.

Tom


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## bill stupak (Oct 12, 2018)

What exactly is the different method?


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## higgite (Oct 12, 2018)

bill stupak said:


> What exactly is the different method?


See post #1 in this thread.

Tom


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## Dabbler (Oct 12, 2018)

When I find the edge of softer plastics like nylon, I reduce my speed to 200 RPM and use my 1/2 " edgefinder.  I haven't noticed any marks, yet!

Nice description, RJ!


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## 9t8z28 (Oct 13, 2018)

I dont like to leave it rub to long either.  I pull up the quill as soon as it kicks out.   I know some guys who put a drop of light oil in between the tip and the part but I dont like that idea. 


Bob Korves said:


> I don't like to leave the cylinder rubbing on the work for long, figuring that will cause wear in and on the edge finder.  I go in once fairly quickly, then once slower, backing out immediately after seeing the number.  On something more fussy I go more slowly, and had most of RJ's excellent and eloquent post figured out, but use it rarely when I am trying really hard to get it right.


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## eugene13 (Oct 13, 2018)

dlane said:


> Cigarette rolling paper works for me, I have an edge finders but the papers are quicker.


Yeah, and you can use them for feeler gauges and lots of other stuff.


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## savarin (Oct 13, 2018)

Never having used an edge finder and doubting if I will ever be able to afford a mill unfortunately I never the less found this a very interesting discussion.
Thanks to all concerned.
(no knowledge is wasted)


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## hmgnz (Oct 14, 2018)

I worked with an old English toolmaker who would normally use the contact until running rue method, however when he was doing more accurate work he would would do as mentioned earlier in this thread of putting a light or white card behind the edgefinder and watch until the light stopped blinking to obtain the edge. He maintained that the way he could guarantee he was within.0001"
Just a little more food for thought...


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## Bob Korves (Oct 14, 2018)

hmgnz said:


> I worked with an old English toolmaker who would normally use the contact until running rue method, however when he was doing more accurate work he would would do as mentioned earlier in this thread of putting a light or white card behind the edgefinder and watch until the light stopped blinking to obtain the edge. He maintained that the way he could guarantee he was within.0001"
> Just a little more food for thought...


Interesting idea, and probably works well, but requires good light, very good eyes, a perfectly parallel with the cutting face viewpoint, and nothing in the line of sight interfering, like perhaps oil, coolant, swarf, or the part itself if it is at all concave.


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## rwm (Oct 14, 2018)

higgite said:


> I have 2 edge finders. One is a Fisher and one is a cheap, generic no name. Both have 3/8” barrels and .20” probes. Just for grins, I experimented a little with both this morning.
> 
> The difference between the Fisher and the generic when using the conventional method to find the edge was ~.0005” (5/10ths).
> 
> ...



Very interesting but can you verify which result was closed to the true edge? .008 is probably unacceptable to most of us. 

Robert


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## BaronJ (Oct 14, 2018)

Hi Guys,

Whilst I don't disagree with the comments made,  RJ is the only one to mention


> The edge finder contact surface and the surface of the edge being found should be clean and  smooth.



Which in my opinion is one cause of the largest errors.


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## BaronJ (Oct 14, 2018)

savarin said:


> Never having used an edge finder and doubting if I will ever be able to afford a mill unfortunately I never the less found this a very interesting discussion.
> Thanks to all concerned.
> (no knowledge is wasted)



They are also useful for finding the centers of pop marks and drill holes with a drill press.
They are also easy to make !


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## higgite (Oct 14, 2018)

rwm said:


> Very interesting but can you verify which result was closed to the true edge? .008 is probably unacceptable to most of us.
> 
> Robert


If you’re asking which method came closest to finding the true edge, I’m not sure how I could verify that with the resources that I have available. But, the Fisher showed only .0006” difference in the 2 methods, which is well within my capability and need for precision. I’m sticking with the conventional method until someone convinces me differently.

If you’re asking which edge finder of my 2 edge finders was closest to finding the true edge, I’m giving the benefit of the doubt to the Starrett over the generic no-name, but again, I have no way to verify that.

I agree that .008" is unacceptable, even for government work.

Tom


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## Dabbler (Oct 14, 2018)

-- So, in summary, the edge needs to be straight (or why find it?), clean, free of any residual oil or anything else bigger than .0002.
-- It seems the most common and agreed method is finding it, and then checking it _at least _once more.


For those with or without a DRO, here's a way to check your Edge finder and your technique (and maybe your DRO setup in the bargain).

*Required:*  Yes - you will need a mill -  an edge finder, a trusted micrometer, and a 1-2-3 block,or  a gauge block or another item that has _parallel_ surfaces.

*Step 1:*  Find the edge on both surfaces, using your lead screw or DRO to make a measurement between them (just like you are using the edge finder to find the centre of the work)

*Step 2:*   then measure the work piece,  using your micrometer.  Your measurements should agree.

I seem to recall in my high school, we did something like this on an unknown block as a test of our technique (45+ years ago!)...
In the above discussions, there is some variance in findings - this is self-proving, and will tell you if the inaccuracies are in the finder or the guy using it


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## RJSakowski (Oct 14, 2018)

After Tom's post about the different results between edgefinders, I tried some of mine.  I found that the Phase II set gave a much smaller jump but that they settled in a "centered" position on backing out about .0014" vs. the .006" for my old Enco.  I suspect that the greater settling distance for returning to a centered position was due to the lighter spring tension in the Enco edgefinder.  It is about 1 lb. vs. 2 lbs. for the Phase  II edgefinders.

All the edgefinders that I tried found the true edge to .0001 or less, measuring a 1-2-3 block verified my micrometer measurement against the DRO reading.  The DRO scales were recently calibrated against an offset verified by micrometer.


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## RJSakowski (Oct 14, 2018)

Dabbler said:


> -- So, in summary, the edge needs to be straight (or why find it?), clean, free of any residual oil or anything else bigger than .0002.
> -- It seems the most common and agreed method is finding it, and then checking it _at least _once more.
> 
> 
> ...


If using the lead screw, you do have to take backlash into account.

I didn't use the Tormach for my experiment because the DRO on the Tormach uses stepper steps from a known position to determine position so it is actually referencing stepper motor rotation.  As such, backlash does enter in and must be accounted for.  

On the other hand, a DRO reading position on a linear scale actually records position.  There is a potential for backlash in the pickup but it is usually quite low by comparison.  

It can be measured as well using a .0001"/div. test indicator.  Mount the indicator in the spindle or to the head and approach a fixed object on the table.  Stop when the indicator is zeroed and zero the DRO.  Back away away and the test indicator should track the DRO.  If it lags behind the amount of lag is the backlash in the DRO.


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## Silverbullet (Oct 18, 2018)

How about the old way of a slip of paper between a cutter and the piece . We were taught many ways to get to the edge.  Mic the paper hold between cutter and part can be running or not or both ways till you get use to it. I used to turn spindle with a wrench and advance table till cutter drags on paper . May not be the super sensitive way but always works . Says a voice from the past.


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## MrWhoopee (Oct 18, 2018)

Silverbullet said:


> How about the old way of a slip of paper between a cutter and the piece . We were taught many ways to get to the edge.  Mic the paper hold between cutter and part can be running or not or both ways till you get use to it. I used to turn spindle with a wrench and advance table till cutter drags on paper . May not be the super sensitive way but always works . Says a voice from the past.



I, too, was taught this method. Just used it recently.


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