Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default edge finder sensitivity

The recent thread on edge finders got me
wondering.

I'm of the 'Spin it at 1000 or so, bring it
slowly to the edge and watch for the "jump""
school.
I have two edge finders, .500 and .200 diameter.
All other things being equal, which is
more accurate in finding an edge? The jump on
the .200 is harder to see, but it almost
seems more consistent.



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Default edge finder sensitivity

I like the 0.200 better. Just personal preference.

Karl


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On Aug 14, 1:55 pm, "BillM" wrote:
The recent thread on edge finders got me
wondering.

I'm of the 'Spin it at 1000 or so, bring it
slowly to the edge and watch for the "jump""
school.
I have two edge finders, .500 and .200 diameter.
All other things being equal, which is
more accurate in finding an edge? The jump on
the .200 is harder to see, but it almost
seems more consistent.


I favor the .200" size but not for accuracy (which I have not compared
between it and the .500)

It's just easier, in my mind, to add .100" to the 'step off'
dimension, rather than .250".

Having said that, I used the .500" one for about 40 years before I
even saw a .200" one.

Lewis.

*****
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Default edge finder sensitivity

On Aug 14, 10:32 pm, "Terry Coombs" wrote:
wrote:
On Aug 14, 1:55 pm, "BillM" wrote:
The recent thread on edge finders got me
wondering.


I'm of the 'Spin it at 1000 or so, bring it
slowly to the edge and watch for the "jump""
school.
I have two edge finders, .500 and .200 diameter.
All other things being equal, which is
more accurate in finding an edge? The jump on
the .200 is harder to see, but it almost
seems more consistent.


I favor the .200" size but not for accuracy (which I have not compared
between it and the .500)


It's just easier, in my mind, to add .100" to the 'step off'
dimension, rather than .250".


Having said that, I used the .500" one for about 40 years before I
even saw a .200" one.


Lewis.


*****


The screws in my mill are 8 tpi . Easier for me to use the .500 , cuz it's
zackly two turns of the wheel to center .
--
Snag
wannabe machinist



I like the .200" dia. edge finder because my feed screws are .200" per
turn and 1/2 turn gets me to the spindle center line :-)).

Here is a question: Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?

Never got to check it myself because the results were usually
workable, but it would be nice to know.

Wolfgang


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Default edge finder sensitivity

wrote:
On Aug 14, 10:32 pm, "Terry Coombs" wrote:
wrote:
On Aug 14, 1:55 pm, "BillM" wrote:
The recent thread on edge finders got me
wondering.


I'm of the 'Spin it at 1000 or so, bring it
slowly to the edge and watch for the "jump""
school.
I have two edge finders, .500 and .200 diameter.
All other things being equal, which is
more accurate in finding an edge? The jump on
the .200 is harder to see, but it almost
seems more consistent.


I favor the .200" size but not for accuracy (which I have not
compared between it and the .500)


It's just easier, in my mind, to add .100" to the 'step off'
dimension, rather than .250".


Having said that, I used the .500" one for about 40 years before I
even saw a .200" one.


Lewis.


*****


The screws in my mill are 8 tpi . Easier for me to use the .500 ,
cuz it's zackly two turns of the wheel to center .
--
Snag
wannabe machinist



I like the .200" dia. edge finder because my feed screws are .200" per
turn and 1/2 turn gets me to the spindle center line :-)).

Here is a question: Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?

Never got to check it myself because the results were usually
workable, but it would be nice to know.

Wolfgang


I've had a mill for like a month now . I'm happy to be on the piece I
wanna machine ...
--
Snag
'90 Ultra "Strider"
'39 WLDD "Popcycle"
Buncha cars and a truck


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Default edge finder sensitivity


....
I have, but my results would not be helpful to others because
particular edgefinders can vary quite a lot.

A well-made edgefinder, e.g. Brown & Sharpe, is quite good. It gets
even better if carefully lapped with fine compound, then carefully
cleaned and lubricated for use.

I trust my best edgefinder to half a thou, though I very rarely need
that kind of accuracy.


Another important factor is what you're mounting the finder in. We use a
dedicated end mill holder and never remove the finder. Put the finder in a
drill chuck and you haven't got much accuracy.

I'm "kick school". My son proved to me that this puts the 0 point 1/2 thou
too far over. "flick it and center school" is more accurate if you've got
young eyes and a serious touch for machine accuracy.

Karl



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Default edge finder sensitivity

On Aug 15, 1:15*am, Don Foreman wrote:
On Thu, 14 Aug 2008 19:43:47 -0700 (PDT),
wrote:...
Here is a question: *Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?

...
Wolfgang
...I trust my best edgefinder to half a thou, though I very rarely *need

that kind of accuracy. *


I checked how repeatable mine was the other day because of this
thread. It repeated to about half a thousandth turning at 600 RPM on a
filed surface and I could get it within a thousandth by feeling for a
step when it was stationary, which is how I use the center finder.
When I want accuracy I surface-grind the block before milling and
drilling. A surface-ground edge seems to behave differently with an
edge finder, maybe it's the friction or lack of it?

I haven't made anything recently that could be used to check the
accuracy of the edge finder. Maybe a carefully bored hole near an edge
would do.
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On Fri, 15 Aug 2008 03:11:49 -0700 (PDT), Jim Wilkins
wrote:

On Aug 15, 1:15*am, Don Foreman wrote:
On Thu, 14 Aug 2008 19:43:47 -0700 (PDT),
wrote:...
Here is a question: *Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?

...
Wolfgang
...I trust my best edgefinder to half a thou, though I very rarely *need

that kind of accuracy. *


I checked how repeatable mine was the other day because of this
thread. It repeated to about half a thousandth turning at 600 RPM on a
filed surface and I could get it within a thousandth by feeling for a
step when it was stationary, which is how I use the center finder.
When I want accuracy I surface-grind the block before milling and
drilling. A surface-ground edge seems to behave differently with an
edge finder, maybe it's the friction or lack of it?

I haven't made anything recently that could be used to check the
accuracy of the edge finder. Maybe a carefully bored hole near an edge
would do.

=========
Anyone have accuracy numbers for the cheapscrew method of using a
dowel pin and feeler gage or slip of paper?


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).


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On Aug 15, 1:25 pm, F. George McDuffee gmcduf...@mcduffee-
associates.us wrote:
On Fri, 15 Aug 2008 03:11:49 -0700 (PDT), Jim Wilkins



wrote:
On Aug 15, 1:15 am, Don Foreman wrote:
On Thu, 14 Aug 2008 19:43:47 -0700 (PDT),
wrote:...
Here is a question: Has somebody here actually TESTED an edgefinder
to determine accuracy and repeatability?
...
Wolfgang
...I trust my best edgefinder to half a thou, though I very rarely need
that kind of accuracy.


I checked how repeatable mine was the other day because of this
thread. It repeated to about half a thousandth turning at 600 RPM on a
filed surface and I could get it within a thousandth by feeling for a
step when it was stationary, which is how I use the center finder.
When I want accuracy I surface-grind the block before milling and
drilling. A surface-ground edge seems to behave differently with an
edge finder, maybe it's the friction or lack of it?


I haven't made anything recently that could be used to check the
accuracy of the edge finder. Maybe a carefully bored hole near an edge
would do.


=========
Anyone have accuracy numbers for the cheapscrew method of using a
dowel pin and feeler gage or slip of paper?

Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).



Unka George, (we're probably a similar age?)

I think that by using a dowel pin in a collet the accuracy of picking
up an edge depends very much on the run-out(TIR)of the collet/pin
combination.

The kick-off type edge locator is much less affected by run-out.

As others have mentioned the surface finish used to locate off is
important; The better the surface finish the smaller the locating
error, up to the point where the inherent process error governs.

The point about lapping the two sliding surfaces on the locator is
also a good idea. If one were really anal one would check the
flatness of these surfaces with an optical flat and a monochromatic
light :-)).

As to whether the kick-off method or 'dead-nuts' concentricity gives
better locating accuracy off an edge... I don't know for sure; but
here is an observation based on physical principles:

1) Two objects cannot occupy the same space at the same time.
2) A 1" diameter pin will not fit into a 1" diameter hole without
force.

Based on this I would venture an opinion that the kick-off method is
more accurate; it is certainly more precise ie. it has greater
repeatability.

..0005" accuracy is, in all likelihood sufficient for most work. I run
at 1000 RPM or so when edge finding, and also place a drop of oil on
the pick-up edge to "improve" things :-)).

Wolfgang
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On Fri, 15 Aug 2008 11:11:03 -0700 (PDT),
wrote:

Unka George, (we're probably a similar age?)

70 years

I think that by using a dowel pin in a collet the accuracy of picking
up an edge depends very much on the run-out(TIR)of the collet/pin
combination.

The kick-off type edge locator is much less affected by run-out.

As others have mentioned the surface finish used to locate off is
important; The better the surface finish the smaller the locating
error, up to the point where the inherent process error governs.

The point about lapping the two sliding surfaces on the locator is
also a good idea. If one were really anal one would check the
flatness of these surfaces with an optical flat and a monochromatic
light :-)).

As to whether the kick-off method or 'dead-nuts' concentricity gives
better locating accuracy off an edge... I don't know for sure; but
here is an observation based on physical principles:

1) Two objects cannot occupy the same space at the same time.
2) A 1" diameter pin will not fit into a 1" diameter hole without
force.

Based on this I would venture an opinion that the kick-off method is
more accurate; it is certainly more precise ie. it has greater
repeatability.

.0005" accuracy is, in all likelihood sufficient for most work. I run
at 1000 RPM or so when edge finding, and also place a drop of oil on
the pick-up edge to "improve" things :-)).

Wolfgang

==========
But of importance only if the edge is flat and parallel to the
axis within 0.0005 inches.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
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Default edge finder sensitivity

snippage
Another important factor is what you're mounting the finder in. We use a
dedicated end mill holder and never remove the finder. Put the finder in a
drill chuck and you haven't got much accuracy.


more snippage

Karl


Actually, it doesn't matter how true the body of an edge finder is running
as the action is only with the tip against the part that you are trying to
locate.

Try it...mount an edge finder in a drill chuck with a 1/32" shim under one
jaw, then locate the same edge without the shim...same location.

Mike


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Default edge finder sensitivity

F. George McDuffee wrote:

(...)
=========
Anyone have accuracy numbers for the cheapscrew method of using a
dowel pin and feeler gage or slip of paper?


I dunno, but as a data point, teenut appears to say one can locate to
within a tenth using oiled tissue paper and a mounted cutter.

http://yarchive.net/metal/edge_finders.html

See entry "Wed, 05 Jan 2000 23:07:11 GMT"

--Winston
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On Aug 16, 3:12 am, Winston wrote:
F. George McDuffee wrote:

(...)

=========
Anyone have accuracy numbers for the cheapscrew method of using a
dowel pin and feeler gage or slip of paper?


I dunno, but as a data point, teenut appears to say one can locate to
within a tenth using oiled tissue paper and a mounted cutter.

http://yarchive.net/metal/edge_finders.html

See entry "Wed, 05 Jan 2000 23:07:11 GMT"

--Winston



George, (I'll be 63 this fall)

I read teenut's article you referred to; in fact I read the whole
list.

When you asked about the accuracy of the dowel pin-in-collet plus
cigarette paper method of edge finding, and if you wanted to locate
the spindle centre line over the edge, then my posting above is
correct in that the collet/spindle/pin run out limits the accuracy of
edge location.

However, after reading teenut's old post it occurred to me that you
may be talking about locating a work piece edge with the edge of a
milling cutter. This is a horse of a different colour because here we
want to determine the EFFECTIVE diameter of the cutter because the
location of any edge machined, from the located edge, is determined by
that EFFECTIVE cutter diameter which includes its wobble and run-out.
The paper-stuck-on-work edge is very effective for this purpose.

I have seen people use feeler gauge stock to do this but I wouldn't do
that to a sharp cutter. Brass shim stock is what I have used for this
purpose because its thickness is easily added to any dimension. With
cigarette paper it is hard to tell how much to allow for; I suppose
for most purposes the .001" thickness of the paper is ignored.

Wolfgang


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On Sat, 16 Aug 2008 08:53:06 -0700 (PDT),
wrote:

On Aug 16, 3:12 am, Winston wrote:
F. George McDuffee wrote:

(...)

=========
Anyone have accuracy numbers for the cheapscrew method of using a
dowel pin and feeler gage or slip of paper?


I dunno, but as a data point, teenut appears to say one can locate to
within a tenth using oiled tissue paper and a mounted cutter.

http://yarchive.net/metal/edge_finders.html

See entry "Wed, 05 Jan 2000 23:07:11 GMT"

--Winston



George, (I'll be 63 this fall)

I read teenut's article you referred to; in fact I read the whole
list.

When you asked about the accuracy of the dowel pin-in-collet plus
cigarette paper method of edge finding, and if you wanted to locate
the spindle centre line over the edge, then my posting above is
correct in that the collet/spindle/pin run out limits the accuracy of
edge location.

However, after reading teenut's old post it occurred to me that you
may be talking about locating a work piece edge with the edge of a
milling cutter. This is a horse of a different colour because here we
want to determine the EFFECTIVE diameter of the cutter because the
location of any edge machined, from the located edge, is determined by
that EFFECTIVE cutter diameter which includes its wobble and run-out.
The paper-stuck-on-work edge is very effective for this purpose.

I have seen people use feeler gauge stock to do this but I wouldn't do
that to a sharp cutter. Brass shim stock is what I have used for this
purpose because its thickness is easily added to any dimension. With
cigarette paper it is hard to tell how much to allow for; I suppose
for most purposes the .001" thickness of the paper is ignored.

Wolfgang

=============
Use your micrometer to verify the paper thickness -- seems to be
very consistent within a packet.

You appear to be correct in that the centerfinder used in the
kick-out mode will compensate for some collet eccetricity, and
does allow for checking under power/rotation, while a dowel pin
and feeler gage will not.

FWIW - I use an electronic edge finder like this one.
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
Anyone have date on these?

Wish I had a Schmidt if only to put in my tool box and look at.
https://www.hermannschmidt.com/produ...&idproduct=148

Also what has the groups experence been with the "audible" edge
finder with a flat ground on the tip to produce a clicking noice?
Less accurate? More accurate? than the standard edge finder?
for examples see
http://www.cartertools.com/fm.html#hfef
(about 2/3s of way down)
http://brownandsharpe.com/precision-...le-edge-finder


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
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F. George McDuffee wrote:

FWIW - I use an electronic edge finder like this one.
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
Anyone have data on these?


Unka George:

This obviously isn't my normal sandbox, but in cruising through here
this thread happened to catch my eye. Here are the relevant portions
of a reply I made to an edge finder thread in amc.

================================================== =============
"Newsgroups: alt.machines.cnc
From: BottleBob
Date: Thu, 07 Apr 2005 01:48:38 GMT
Subject: just how good are electronic edge finders?


Paul:

The solid stem electric edge finder is junk IMO. They run out
even
when new and all you have to do is overtravel a little too much and you
tweak them. Electric edge finders are used with the spindle not
turning. I also have a ball tip electric edge finder that I use from
time to time but here too, you have to touch off your part, record the
axis dimension then turn the edge
finder 180 degrees and touch off again and subtract one dimension from
the other and divide by 2 and move that amount to get the correct edge
reading because they run out a little also. The thing about the ball
type is it's
spring loaded so if you overtravel a little you're not going to do it
much damage.
================================================== =============


Also what has the groups experence been with the "audible" edge
finder with a flat ground on the tip to produce a clicking noice?
Less accurate? More accurate? than the standard edge finder?
for examples see
http://www.cartertools.com/fm.html#hfef
(about 2/3s of way down)
http://brownandsharpe.com/precision-...le-edge-finder


I bought a couple of those "audible" edge finders that make a
clicking noise when they "kick-out". They are not very loud in a noisy
shop environment. They have a small flat ground on the edge finder. I
tried them a few times but the spinning flat has a tendency to dig into
soft materials, so I don't bother to use them
anymore.

The following bears on how the accuracy of an edge finder is
influenced by the concentricity of the edge finder body.
From an amc thread in 2003:

================================================== ================
Yesterday I made a $5.00 bet with another machinist, here is
what it entails.
Picture a 1/2" shank edge finder (.200 tip) in an ER 32 collet
holder. Find the edge of a part to the nearest .0001, zero the axis.
Take out the holder and put a narrow .010 brass shim between ONE side
of the edge finder and the collet to simulate some severe runout. Re
edge-find the same edge of the same part as before. Look to see how
far off the axis reading is from before. I said it will probably be
within .001 of the prior reading. We didn't have time to physically
test this yesterday, but probably will Monday.
Will I be $5.00 richer, or should I go try to dig up 500 pennies to
pay off my gambling debt? g



OK, here's what happened with the bet at work today. I took a 1/2"
shank edge finder and put it in an ER-32 collet holder (made sure
everything was clean with no mico chips that I could see), scaled the
edge finder 1" from the top of the collet (I wanted to minimize any
possible exaggeration if the collet taper or holder taper were off a
little bit. Cleaned the spindle. Indicated a 1-2-3 block in the vise
and cleaned out the spindle taper and installed the holder and edge
finder. Called over my betting opponent and a witness that held
the
money, just a formality. Brought the Z axis down to -9.880 (recorded
that figure so I could come to the same setting later), edge found the
1-2-3 block and zero'd the readout. Took the holder out of the machine
and turned it 180 degrees to see if there was a difference, it was off
about a .0001, no biggie.
Took the tool holder out and went and made up a .015 think
brass shim.
The shim was about .400 wide and a little longer that the collet, I
pre-bent it in a V-block with a transfer punch. Put the shim and the
edge finder in the collet, not an easy fit, scaled the edge finder 1"
from the collet. Tightened it up and went to the machine with my
entourage. Brought the Z down to -9.880 and fed the edge finder over in
..010 increments, then .001 increments, then .0001 increments until it
kicked out. It ended up being .0001 different than the original edge
find. Much cheering, dancing, and commotion was seen and heard coming
from MY corner!
My betting buddy was pretty convinced but he wanted to try it
in a
drill chuck (just in case I had rigged the collet to tilt the precise
amount the get my reading), we put the shim on one of the three chuck
jaws, inserted the edge finder, tightened it, and went back to the
machine. To make a long story short it was out .0002 from the original
edge find. He was convinced, and took his loss gracefully. A fine time
was had by one and all. LOL
BTW, I plan to use my windfall profits to buy donuts for the shop
tomorrow morning.
================================================== =================


--
BottleBob
http://home.earthlink.net/~bottlbob

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On Sat, 16 Aug 2008 19:08:24 -0700, BottleBob
wrote:

snip
My betting buddy was pretty convinced but he wanted to try it
in a
drill chuck (just in case I had rigged the collet to tilt the precise
amount the get my reading), we put the shim on one of the three chuck
jaws, inserted the edge finder, tightened it, and went back to the
machine. To make a long story short it was out .0002 from the original
edge find. He was convinced, and took his loss gracefully. A fine time
was had by one and all. LOL
BTW, I plan to use my windfall profits to buy donuts for the shop
tomorrow morning.
================================================= ==================

Thanks for the insight and some real world experience and numbers
-- much better than opinions.

FWIW -- I have always had the spindle turning [c. 500 rpm] when
using the electronic edge finder. Also very careful sneaking up
to a contact. Light is not very bright though when it makes
contact.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
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F. George McDuffee wrote:

FWIW -- I have always had the spindle turning [c. 500 rpm] when
using the electronic edge finder. Also very careful sneaking up
to a contact. Light is not very bright though when it makes
contact.


Unka George:

If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
..001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout


--
BottleBob
http://home.earthlink.net/~bottlbob

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On Aug 17, 5:57 am, BottleBob wrote:
F. George McDuffee wrote:
FWIW -- I have always had the spindle turning [c. 500 rpm] when
using the electronic edge finder. Also very careful sneaking up
to a contact. Light is not very bright though when it makes
contact.


Unka George:

If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
.001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout

--
BottleBobhttp://home.earthlink.net/~bottlbob




I don't want to sound nit-picky about this but to be really certain
about the effect of excentricity of the edge locator, the 180 degree
turn-around test described above would need to be repeated at 90
degrees from the first tests. Unless, of course, you were really sure
that at the first trial you indeed were at the high point of any
excentricity.

Wolfgang


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Default edge finder sensitivity

On Sun, 17 Aug 2008 02:57:14 -0700, BottleBob
wrote:



F. George McDuffee wrote:

FWIW -- I have always had the spindle turning [c. 500 rpm] when
using the electronic edge finder. Also very careful sneaking up
to a contact. Light is not very bright though when it makes
contact.


Unka George:

If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
.001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout

==========
Good observations, but as an old German tool maker told me years
ago, after I took a drawing to him with 4 place decimals for some
hole locations, if you can't measure it, it doesn't matter.

I see several people have mentioned the Schmidt edge finders,
https://www.hermannschmidt.com/produ...&idproduct=148
anyone have comments on /experience with the ones from Flexbar?
http://67.59.156.7/merchant2/merchan...uct_Code=18509

Are these that much better than B&S or Starrett, or just more
expensive?


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
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Default edge finder sensitivity



wrote:
On Aug 17, 5:57 am, BottleBob wrote:


If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
.001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout



I don't want to sound nit-picky about this but to be really certain
about the effect of excentricity of the edge locator, the 180 degree
turn-around test described above would need to be repeated at 90
degrees from the first tests. Unless, of course, you were really sure
that at the first trial you indeed were at the high point of any
excentricity.


Wolfgang:

You wouldn't need to know, or be, on the maximum high point of any
eccentricity to average out the runout in one axis. Let me try to
explain it this way. Let's say the edge finder was bent toward the X+
side by +.001, so therefore the X- side would be bent away by -.001.
Now when you touched the X+ side, (recorded your reading) then turned
the edge finder 180 degrees and touched it again you'd have
theoretically have a .002 difference. So half that difference would be
roughly the center of the runout and spindle. Now the Y+ side of the
edge finder could be +.005 and the Y- side could be -.005, BUT they
don't necessarily influence the amount of runout in the X+ and X- sides.
Was that clear as mud, or did it help?

One thing that "could" influence the measurement of runout would be
the the angle of the stem. If the very tip was touched on one side,
and the other side was touched further up the stem due to being bent
over... then the true runout would be skewed. Is this type of
situation the ball tip electric edge finders would nullify any "bent
tip" inaccuracies.


--
BottleBob
http://home.earthlink.net/~bottlbob

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Default edge finder sensitivity



F. George McDuffee wrote:
On Sun, 17 Aug 2008 02:57:14 -0700, BottleBob
wrote:


If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
.001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout

==========
Good observations, but as an old German tool maker told me years
ago, after I took a drawing to him with 4 place decimals for some
hole locations, if you can't measure it, it doesn't matter.


Unka George:

It might pay to indicate your electric edge finder from time to time,
and tap it to get it centered if it runs out an appreciable amount.
As far as the needed accuracy for your job, that depends on the job.
Some can be scaled, some can be within a few thou, and some need to be
within .0005. In the latter case I wouldn't count on the accuracy of
electric edge finders, I'd either use a regular edge finder or
indicator sweep your part and move over half the distance of your part.


I see several people have mentioned the Schmidt edge finders,
https://www.hermannschmidt.com/produ...&idproduct=148
anyone have comments on /experience with the ones from Flexbar?
http://67.59.156.7/merchant2/merchan...uct_Code=18509

Are these that much better than B&S or Starrett, or just more
expensive?


I never felt the need to buy an edge finder more expensive than a good
Starrett or B&S. So with the knowledge of me having no direct
experience with Herman Schmidt or Flexbar edge finders... my OPINION
would be that your money would be better spent in another area. IF you
need better accuracy than a good Starrett edge finder can achieve
(around ±.0005) then you need to consider using an indicator to find
the edge of your part, either by "sweeping", direct indicating the
edge, or using a "chair".

http://www.wttool.com/product-exec/p...m_source=froog

In using those you have to make sure the wall you're edge finding is
perpendicular to your table or you might get an angular error.

--
BottleBob
http://home.earthlink.net/~bottlbob

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Default edge finder sensitivity

On Aug 17, 4:55 pm, BottleBob wrote:
F. George McDuffee wrote:
On Sun, 17 Aug 2008 02:57:14 -0700, BottleBob
wrote:
If the electric edge finder is spinning, AND if it runs out a little,
it will probably light up when the high point contacts a conducting
surface. But you really won't know if that high point is .0001",
.001", or even .010" off center. That's why I would contact your part
with the edge finder stopped (then zero out your axis), back off your
part, turn the edge finder 180 degrees and contact your part again to
see if there is a difference in the two positions of the edge finder.
Half that distance difference should be your off-center runout

==========
Good observations, but as an old German tool maker told me years
ago, after I took a drawing to him with 4 place decimals for some
hole locations, if you can't measure it, it doesn't matter.


Unka George:

It might pay to indicate your electric edge finder from time to time,
and tap it to get it centered if it runs out an appreciable amount.
As far as the needed accuracy for your job, that depends on the job.
Some can be scaled, some can be within a few thou, and some need to be
within .0005. In the latter case I wouldn't count on the accuracy of
electric edge finders, I'd either use a regular edge finder or
indicator sweep your part and move over half the distance of your part.

I see several people have mentioned the Schmidt edge finders,
https://www.hermannschmidt.com/produ...sp?idcategory=....
anyone have comments on /experience with the ones from Flexbar?
http://67.59.156.7/merchant2/merchan...uct_Code=18509


Are these that much better than B&S or Starrett, or just more
expensive?


I never felt the need to buy an edge finder more expensive than a good
Starrett or B&S. So with the knowledge of me having no direct
experience with Herman Schmidt or Flexbar edge finders... my OPINION
would be that your money would be better spent in another area. IF you
need better accuracy than a good Starrett edge finder can achieve
(around ±.0005) then you need to consider using an indicator to find
the edge of your part, either by "sweeping", direct indicating the
edge, or using a "chair".

http://www.wttool.com/product-exec/p..._medium=cpc&ut....

In using those you have to make sure the wall you're edge finding is
perpendicular to your table or you might get an angular error.

--
BottleBobhttp://home.earthlink.net/~bottlbob



Bottlebob:

Excuse the 'senior moment' on my part regarding the 90 degree babble.
You are of course correct.

As to geometric accuracy of the various features: Anyone who reads
this ought to understand that attention to spindle squareness to the
table, straight tool, work ref. surface finish and squareness is
mandatory for accurate results. The latter is particularly important
when using the 'chair gauge' you referenced. No sense in measuring
the surface finish of a plowed field in micro-inches:-)).

Jig borer operator in my training grounds used a gauge block held to
the side of the work. First they swept the work edge and then the
gauge block surface with the indicator. When the indicator needle
stopped moving the spindle centre line was dead-nuts over the
reference edge, say within .0001 or so. The beauty of this method is
that no tooling errors are introduced into the process. Theoretically
it may be used to achieve any accuracy required.

Wolfgang


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wrote:

On Aug 17, 4:55 pm, BottleBob wrote:


IF you
need better accuracy than a good Starrett edge finder can achieve
(around ±.0005) then you need to consider using an indicator to find
the edge of your part, either by "sweeping", direct indicating the
edge, or using a "chair".


Bottlebob:

Excuse the 'senior moment' on my part regarding the 90 degree babble.
You are of course correct.


Wolfgang:

Is that really your name? It's pretty cool if it is. Anyway, we all
make the occasional conceptual boo-boo, it's no biggie.


As to geometric accuracy of the various features: Anyone who reads
this ought to understand that attention to spindle squareness to the
table, straight tool, work ref. surface finish and squareness is
mandatory for accurate results. The latter is particularly important
when using the 'chair gauge' you referenced.


Actually, I've got a magnetic "chair" and the "corner finder", but I
seldom use them for the very reasons you mentioned above. Possible out
of square issues.

Jig borer operator in my training grounds used a gauge block held to
the side of the work. First they swept the work edge and then the
gauge block surface with the indicator. When the indicator needle
stopped moving the spindle centre line was dead-nuts over the
reference edge, say within .0001 or so. The beauty of this method is
that no tooling errors are introduced into the process. Theoretically
it may be used to achieve any accuracy required.


Correct, and that particular method was what I was referring to when I
mentioned "direct indicating the edge". And of course a "tenth"
indicator is sometimes used when the tolerance requires it.

Wolfgang


--
BottleBob
http://home.earthlink.net/~bottlbob

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Default edge finder sensitivity

I think you are a bit picky. That is what I was talking about.
The ionic isn't just liquids. If you have a molecule of Iron and in
the mix is anything else (as in always) some part will be attached to Fe
and the other part hanging out for something to bond to. Think of Carbon
it can have Hydrogen attached or sulfur..... so a non-balanced molecule would
be making an ionic bond to fill the requirements.

Any part has error in the edge. The bar that is used to touch the sides
has lots of errors in the 'so called' round bar. Might be an oval, a D or

The flat of the 'chair' all sides have tolerances. Mixed with the 'bar' and
this becomes a rich set of offsets. Mixed with a tilt of any kind or reason
and it becomes richer in offsets with one or more angles causing a touch point
to be different down the edge.

In general the fast helpers are used when tolerance is tight. If you are
making something for a shovel, than it wouldn't really matter.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


BottleBob wrote:


Martin H. Eastburn wrote:

Precision measurements - maybe outside your area - are made with
blocks.


Martin:

I think the term you're looking for is gage blocks, or Jo blocks
(short for Johansson blocks). As far as "...maybe outside my area"; I
probably have at least a passing familiarity in the use of Jo blocks as
I've been wringing stacks of them together since my Tool & Die
apprenticeship days in the early 70's. Currently, as an employee I
have, and use, my own set of round Jo blocks plus use the shop's square
set on a regular basis.


The blocks are often in two or three materials and all hold
by ionic or molecular forces.


An example of an ionic bond is sodium chloride.

The wringing, and adhesion of, Jo blocks is a phenomenon that has a
number of possible hypotheses. Covalent bonding, metallic bonding, van
der Waals force, Casimir effect, the expulsion of air between the
surfaces and resulting 14 psi holding force, surface tension of water or
oil, or a combination of any of the above or other factors not listed.


So if there is a little coolant or sliver under an edge and a bur
is within the corner relief - the coolant will hold off the edge
providing
some level of error. Then there are inherent errors on all edges
including
the touching edge of the finder.


I'm not sure what the relevance of wringing Jo blocks is to putting
a "chair" indicating device on the side of a part. But I'll certainly
concede that burrs, slivers, and debris could throw off accuracy if they
weren't cleaned off first.
As I stated elsewhere in this thread, I don't often use the "chair"
device due to it's, IMO, greater chance of introducing possible error.
Often from tapered part edges.




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Default edge finder sensitivity

On Thu, 14 Aug 2008 18:55:22 GMT, "BillM"
wrote:

The recent thread on edge finders got me
wondering.

=============
Some URLs of interest about edge finders.

First US patent appears to be in 1934

Some edge finder URLS of interest

Cole et al in U.S. Pat. No. 1,984,864
http://www.google.com/patents/pdf/RE...OzWgMOKNVkSzSw

Patent number: 2451904
Filing date: Jul 15, 1946
Issue date: Oct 1940
http://www.google.com/patents/pdf/LO...Py4iCLGES0v7Rw

Moore chair Item # 3070-A Edgefinder, Inch
$4,110.00

http://mooretool.thomasnet.com/item/...070-a?&seo=110

http://videos.findtarget.com/free_vi...dg/Using_Edge/

http://findarticles.com/p/articles/m...0/ai_n24384929

http://www.stanford.edu/group/prl/cg...le=Edgefinders


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).
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