What is the proper technique for using an edgefinder in a vertical milling
machine? For this example, I'm using one with a 0.200 inch diameter
projection, thus 0.100 inch offset from true centerline. Prior to making
contact, the 0.200 extension is off center, but a soon as contact with the
work piece is made, it seems to be now rotating true (machine is running
under power about 150 rpm). Ok, now set x or y graduated dial to zero. BUT,
what happens if I advance the table, say another couple of thousands? How
can I be sure that the first contact is correct if I can still move the work
a tiny bit closer to the indicator without anything happening? Tool made in
India (no instructions); Machinery's Handbook says nothing about
edgefinders. HELP!

"David Anderson" wrote in message
igy.com...
What is the proper technique for using an edgefinder in a vertical milling
machine? For this example, I'm using one with a 0.200 inch diameter
projection, thus 0.100 inch offset from true centerline. Prior to making
contact, the 0.200 extension is off center, but a soon as contact with the
work piece is made, it seems to be now rotating true (machine is running
under power about 150 rpm). Ok, now set x or y graduated dial to zero.
BUT,
what happens if I advance the table, say another couple of thousands? How
can I be sure that the first contact is correct if I can still move the
work
a tiny bit closer to the indicator without anything happening? Tool made
in
India (no instructions); Machinery's Handbook says nothing about
edgefinders. HELP!



I did a google search for "How to use an edge finder" and got 7 hits, here
is one that looks pretty good.
http://www.metalwebnews.com/howto/edge/edgefind.html

Lane

In article . com, David
Anderson says...

What is the proper technique for using an edgefinder in a vertical milling
machine?

Bring the finder in to contact the edge.

Wind in the slide until the finder runs true,
by eye.

Continue winding in until the 0.200 projection
moves to an offset postion and stops running true.
At the instant it does, your spindle axis is
0.1 inch from the edge.

Just creep up on it, and keep re-zeroing
the dial or DRO until the edge finder
snaps off-center.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

The article Lane mentiones is an excellent guide.

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

Some suggestions to add. If you are setting up on a Bridgeport mill
or other brand where one turn of the leadscrew gives .200 of movement
set the dial to 100 when the edge finder kicks. That way when you
move the table .100 you will be over the edge of the part AND the dial
will be at 0 instead of being at 100. This assumes a .200 end on the
edgefinder.

Also, run edge finders at about 1000 RPM for better results. Check
and recheck after setting the dial. On a Bport it is easy to move the
table slightly when tightening the knurled collar. Better to recheck
than wish you had!

If using a double ended edgefinder in a collet be VERY careful when
removing it! It is easy for the .500 end to get hung up in the
collett and if you pull it hard the spring inside gets very long.
Don't ask how I know this. I always (now) remove them from the
collett by removing the collett from the spindle and pushing the
edgefinder out with a slender rod.

If you have a DRP always be in the habit of setting your dials to zero
when setting up. If the power blinks out and you haven't done so you
may be up the creek. When I did industrial modelmaking for a living
often times the pick up point would be machined away and without a
good set up I would have been lost after a power outage.

Errol Groff
Instructor, Machine Tool Department
H.H. Ellis Tech
613 Upper Maple Street
Danielson, CT 06239

860 774 8511 x1811

http://pages.cthome.net/errol.groff/

http://newenglandmodelengineeringsociety.org/




On Tue, 11 Nov 2003 18:31:45 GMT, "David Anderson"
wrote:

What is the proper technique for using an edgefinder in a vertical milling
machine?

"jim rozen" wrote in message
...
In article . com, David
Anderson says...

What is the proper technique for using an edgefinder in a vertical
milling
machine?

Bring the finder in to contact the edge.

Wind in the slide until the finder runs true,
by eye.

Continue winding in until the 0.200 projection
moves to an offset postion and stops running true.
At the instant it does, your spindle axis is
0.1 inch from the edge.


1/10th of an inch?! Really?!

"lane" lane_nospam@copperaccents_dot_com wrote in message
...

"jim rozen" wrote in message
...
In article . com, David
Anderson says...

What is the proper technique for using an edgefinder in a vertical
milling
machine?

Bring the finder in to contact the edge.

Wind in the slide until the finder runs true,
by eye.

Continue winding in until the 0.200 projection
moves to an offset postion and stops running true.
At the instant it does, your spindle axis is
0.1 inch from the edge.


1/10th of an inch?! Really?!


Please ignore my last post, major brain fart!

In article , lane says...

Please ignore my last post, major brain fart!



Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

In article , Errol Groff says...

If using a double ended edgefinder in a collet be VERY careful when
removing it! It is easy for the .500 end to get hung up in the
collett and if you pull it hard the spring inside gets very long.
Don't ask how I know this. I always (now) remove them from the
collett by removing the collett from the spindle and pushing the
edgefinder out with a slender rod.

If using these in an NC machine it pays to remember it's
there in the spindle. At the former night job, they had
several edge finder-shaped divots in the aluminum vise
jaws!

If you have a DRP ...

Hmm. I may be old, but I ain't drping yet....

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Darn. I read and re-read postings and still manage to let things like
that slip through.

OTOH, if you have never DRPed you haven't truly lived.

Errol


On 11 Nov 2003 16:00:01 -0800, jim rozen

If you have a DRP ...

Hmm. I may be old, but I ain't drping yet....

Thanks to all for good comments - the link to the article by Mike Rehmis
entitled "Edge Finder" was right on target. Also, his comments about a
cheap tool being useless (which is what I was using) made perfect sense. So,
I immediately bought a Starrett #827A which is much better. But, all these
comments evidently assume that we are locating a straight surface from the
spindle centerline. What about locating a curved, internal edge of a hole?
Maybe that was my problem. I was attempting to locate the edge of a 0.402
inch diameter hole with the 0.200 tit on the finder. The "kick" now depends
on the direction of rotation of the tool and whether the curved surface
being contacted is coming nearer or further away during the "kick". Thanks
once again. Dave

"David Anderson" wrote in
gy.com:

Thanks to all for good comments - the link to the article by Mike
Rehmis entitled "Edge Finder" was right on target. Also, his comments
about a cheap tool being useless (which is what I was using) made
perfect sense. So, I immediately bought a Starrett #827A which is much
better. But, all these comments evidently assume that we are locating
a straight surface from the spindle centerline. What about locating a
curved, internal edge of a hole? Maybe that was my problem. I was
attempting to locate the edge of a 0.402 inch diameter hole with the
0.200 tit on the finder. The "kick" now depends on the direction of
rotation of the tool and whether the curved surface being contacted is
coming nearer or further away during the "kick". Thanks once again.
Dave




David,
You need a centering indicator for finding the center of holes. This
mounts in the spindle, the dial is rubber-banded to some projection on the
quill housing to keep it from rotating. The indicator tip (much like a last
word) is swept in the hole using the spindle rotated by hand. Kind of like
indicating a part in a lathe...backwards, the indicator is spinning instead
of the part.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

"Errol Groff" wrote in message
...

If you have a DRO always be in the habit of setting your dials to
zero when setting up. If the power blinks out and you haven't
done so you may be up the creek. When I did industrial modelmaking
for a living often times the pick up point would be machined away
and without a good set up I would have been lost after a power outage.

[Note: I corrected "DRP" in the text above to "DRO" to avoid further
confusion.]

That's a good tip Errol. Another one is to buy an Uninterruptable Power
Supply (UPS) for your DRO. This is also commonly known as a battery back-up
power supply. This serves several benefits:

1. If the power blacks out (or browns out) briefly, you lose nothing. The
DRO can remain powered on.

2. If the power blacks out (or browns out) for an extended period, you have
time (using the battery back-up) to position your table back to the origin
(zero/zero) and lock it down. Then you can shut off the DRO and wait for the
mains power to return.

3. Quality UPS's have superior AC line filtering, thus protecting your
expensive DRO from the line noise and transients that are common in a shop
(due to motors and such).

It used to be that a decent UPS was very expensive, but with the
proliferation of personal computers, that is no longer the case. A DRO
typically doesn't draw much power, so you don't need a large UPS. I highly
recommend the UPS's made by APC (American Power Conversion). No affiliation,
etc., but I have used them extensively on servers and workstations for many
years with great success, and now have one powering my DRO. Also, APC offers
a lifetime warranty on the UPS *and* the protected equipment from any damage
caused by electrical surges, spikes, or even lightning.

- Michael

What Jim said, but I'll add that the cheap imports I've seen (like those
from India) don't seem nearly as crisp to use as a good domestic like
Starrett.

"David Anderson" wrote in message
igy.com...
What is the proper technique for using an edgefinder in a vertical milling
machine? For this example, I'm using one with a 0.200 inch diameter
projection, thus 0.100 inch offset from true centerline. Prior to making
contact, the 0.200 extension is off center, but a soon as contact with the
work piece is made, it seems to be now rotating true (machine is running
under power about 150 rpm). Ok, now set x or y graduated dial to zero.
BUT,
what happens if I advance the table, say another couple of thousands? How
can I be sure that the first contact is correct if I can still move the
work
a tiny bit closer to the indicator without anything happening? Tool made
in
India (no instructions); Machinery's Handbook says nothing about
edgefinders. HELP!

For hole location you might want to investigate a co-axial indicator. Blake
makes a good one for around $150-200 or there are imports available at half
that price. They are also handy for aligning the TS on a lathe and can be
used to locate a cylidrical projection on a workpiece. They are graduated
to 0.0005" and probably accurate to 0.001-0.002", maybe a little better.

"David Anderson" wrote in message
gy.com...
Thanks to all for good comments - the link to the article by Mike Rehmis
entitled "Edge Finder" was right on target. Also, his comments about a
cheap tool being useless (which is what I was using) made perfect sense.
So,
I immediately bought a Starrett #827A which is much better. But, all these
comments evidently assume that we are locating a straight surface from the
spindle centerline. What about locating a curved, internal edge of a
hole?
Maybe that was my problem. I was attempting to locate the edge of a 0.402
inch diameter hole with the 0.200 tit on the finder. The "kick" now
depends
on the direction of rotation of the tool and whether the curved surface
being contacted is coming nearer or further away during the "kick".
Thanks
once again. Dave

I had the same trouble a few months ago and decided to machine a block of
steel to a known accurate surface, then using digital readouts use a
centre-finder to see if it would correctly indicate the centre. It varied by
about 0.2mm ( about 8 thou ) through about 10 trials. First I used the
methode of slowly creeping to wards the edge until the end went still (
concentric ) and then tried going past this point until it suddenly flicked
out. Both methods didn't seem to offer any better reliability. So I went
back to my old ground steel bar held in an autolock chuck. That never lies.

Dean.

"David Anderson" wrote in message
igy.com...
What is the proper technique for using an edgefinder in a vertical milling
machine? For this example, I'm using one with a 0.200 inch diameter
projection, thus 0.100 inch offset from true centerline. Prior to making
contact, the 0.200 extension is off center, but a soon as contact with the
work piece is made, it seems to be now rotating true (machine is running
under power about 150 rpm). Ok, now set x or y graduated dial to zero.
BUT,
what happens if I advance the table, say another couple of thousands? How
can I be sure that the first contact is correct if I can still move the
work
a tiny bit closer to the indicator without anything happening? Tool made
in
India (no instructions); Machinery's Handbook says nothing about
edgefinders. HELP!

David Anderson wrote:

Thanks to all for good comments - the link to the article by Mike Rehmis
entitled "Edge Finder" was right on target. Also, his comments about a
cheap tool being useless (which is what I was using) made perfect sense. So,
I immediately bought a Starrett #827A which is much better. But, all these
comments evidently assume that we are locating a straight surface from the
spindle centerline. What about locating a curved, internal edge of a hole?
Maybe that was my problem. I was attempting to locate the edge of a 0.402
inch diameter hole with the 0.200 tit on the finder. The "kick" now depends
on the direction of rotation of the tool and whether the curved surface
being contacted is coming nearer or further away during the "kick". Thanks
once again. Dave

I use an edge finder quite regularly to find c/line of holes. Works quite well,
actually. Generally not for smallish diameters like you mentioned.

michael

jim rozen wrote:

In article , Errol Groff says...

If using a double ended edgefinder in a collet be VERY careful when
removing it! It is easy for the .500 end to get hung up in the
collett and if you pull it hard the spring inside gets very long.
Don't ask how I know this. I always (now) remove them from the
collett by removing the collett from the spindle and pushing the
edgefinder out with a slender rod.

If using these in an NC machine it pays to remember it's
there in the spindle. At the former night job, they had
several edge finder-shaped divots in the aluminum vise
jaws!

Geez. What were they doing, practicing to get it right? I think I have only
trashed 2 in 33 years.

michael



If you have a DRP ...

Hmm. I may be old, but I ain't drping yet....

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Hey Dave,


If you think about what is actually happening, it's easy to work with.
Mind you it's far easier with a DRO than without, but recall that
edgefinders have been around a LOT longer that DRO's.

I have found that when you start the spindle up to find an edge the
tip of the edgefinder should be "flicked" with a finger so as to have
a quite definite "wobble". I know you can't "see it" as so, but this
eccentric wobble will tend to act like a fixed lobe on a cam, in that
it will tend to remain in one place on the edgefinder relative to the
edgefinder body, so to speak. As you approach and the tip of the
edgefinder contacts the edge of the work, the tip will get pushed
over to become less and less eccentric and more and more concentric,
until it's impossible to visually see any eccentricity. But the
eccentricity is still there, ever so slightly. Your moving the table
is pushing the tip closer and closer to being centred, and it does so
because it "can" get less and less eccentric. But as soon as the
edgefinder does reach concentricity, that is it becomes centred, then
any motion past that point will cause eccentricity to occur again.
But this "new" eccentricity cannot remain in one place relative to
the edgefinder body as it did on the approach. The over-centering
causes the eccentricity to occur in one place relative to the work
face instead, so the edgefinder seems to "kick" over immediately.
That is the point you are looking for. That ever so slight movement
of the handwheel causing the kick. Accurate to at least a thou, and
it is also in a dynamic mode, so accounts even for a non-concentric
spindle, or collet, or holder, or drill-chuck, too. That's why it is
best to chuck the edgefinder in whatever holder or drill chuck that
you intend to use for cutting.

As to finding the centre of a hole, it can be tougher to see, but
really all you have to do is get a rough location, move the table so
you get kick on one direction, then traverse only that axis in the
opposite direction until you get kick again, note the difference in
the two points and halve it. Move the table to this "halved" point,
then do the other axis the same way. Now the hole should be fairly
close to centre. Then do them both again, then once again, and this
last time the halving will now give you the centre. This is only
easily possible with a DRO. With a bit of math, you can even
determine how close you are by the motion distance required to see the
kicks, as it should be hole diameter minus edgefinder diameter divided
by 2. For example, presuming you know that the hole diameter is say
..375, and the edgefinder tip is .200, then when starting correctly
centred on either axis the kick point should occur at [ (0.375" -
0.200") / 2 = 0.0875"] of motion in either direction along either
axis. You can even reverse this theory, and find the centre then note
the motions and that will give you a really good indication as to hole
diameter, and even as to concentricity, in that all movements from
centre to kick point should be equal.

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXXXXXXXXXXX
On Wed, 12 Nov 2003 03:11:43 GMT, "David Anderson"
wrote:

Thanks to all for good comments - the link to the article by Mike Rehmis
entitled "Edge Finder" was right on target. Also, his comments about a
cheap tool being useless (which is what I was using) made perfect sense. So,
I immediately bought a Starrett #827A which is much better. But, all these
comments evidently assume that we are locating a straight surface from the
spindle centerline. What about locating a curved, internal edge of a hole?
Maybe that was my problem. I was attempting to locate the edge of a 0.402
inch diameter hole with the 0.200 tit on the finder. The "kick" now depends
on the direction of rotation of the tool and whether the curved surface
being contacted is coming nearer or further away during the "kick". Thanks
once again. Dave

For locating holes at school we mount a dial test indicator in the
spindle, then move the table around until the dial reads 0 all the way
around the hole when the spindle is rotated.

For finding edges we have a beeping edge finder - when the ball on the
edge-finder makes contact with the workpiece it completes a circuit or
whatever and makes it beep. I've used it a few times, but mostly I've
been using a 20 thou feeler gauge and bringing the cutter in (with the
power off!) until the feeler gauge is just barely snug between the
cutter and the workpiece. Add 20 thou plus half the diameter of the
cutter and the middle of the spindle is over the edge of the workpiece.
I'm not sure how accurate this method really is, but I haven't had any
problems so far.


chem

David Anderson wrote:
Thanks to all for good comments - the link to the article by Mike Rehmis
entitled "Edge Finder" was right on target. Also, his comments about a
cheap tool being useless (which is what I was using) made perfect sense. So,
I immediately bought a Starrett #827A which is much better. But, all these
comments evidently assume that we are locating a straight surface from the
spindle centerline. What about locating a curved, internal edge of a hole?
Maybe that was my problem. I was attempting to locate the edge of a 0.402
inch diameter hole with the 0.200 tit on the finder. The "kick" now depends
on the direction of rotation of the tool and whether the curved surface
being contacted is coming nearer or further away during the "kick". Thanks
once again. Dave




--

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