I?ve done it now. The cross slide on my lathe has been giving me
problems. I hesitated to do anything because it meant that I had to
remove the DRO scale. My cross slide is now working like new. But even
though I handled the scale as if it were nitroglycerine, my worst fears
have come true. When I reassembled everything, the read out now reads
0.000 no mater what the position on the cross slide is in. The other
scale, that I didn?t touch works fine, as does the receiving unit.
I was not aware that Sargon is no longer in business. Now what do I do?
Anyone have an idea on how I can fix this thing? I really don?t have a
budget for a new DRO.
The scale itself is a Sargon LG330-8. Are scales of different brands
The scales are much sturdier than you might think. Are you sure you got the
alignment of the reader head right? There's a link between the actual reader
head (the part inside that slides on the glass scale itself) and the part
outside that attaches to the machine. The link is rigid only in the axis that
is being measured and is flexible in the other 5 (2 linear, 3 angular) so that
the head aligns itself to the scale. Most scales are tolerant of a reasonable
amount of misalignment, but will act as you describe if the alignment is too
You may be able to get some tips on alignment on Acurite's website.
Most scales, but by no means all, are TTL level and interchangeable, though
connectors and pinouts may not be compatible. The scale also needs to match one
of the available resolutions on the readout.
The Sargon readouts that I have seen are quite adjsutable for the
I have a Sargon readout, and a Heidenhain scale, and Hiedenhain
Most scales are TTL, and the signals are compatible, and just need new
connectors, or adapters made.
The Heidenhain scales that I used are not TTL compatible, but the
interpolator box does convert them from analog to TTL. At that point
they plug into a Sargon, or AcuRite, ir whatever box. Teh point being,
I set up the Heidenhain scales for .0005 mm resolution, and the Sargon
readout was able to accomodate that resolution. Now, my Diameter reads
out to .0001" (That Diameter, and thats that many zeroes!!)
I don't know what is wrong with your scale. It is possible to
troubleshoot it, but I can't type fast enought to write the book on it,
before I am late for something else.
Surely something you can do, with a little exploration.
Maybe try here:
the Sargon scales have some electronics right insode the DB25
connector that plugs into the readout.
If the readout head is not lined up, it will not see the grating on the
glass scale, and won't "move". If any wires to the readout head break,
it will not work..
Look it over very carefully.
The majority (only?) problems I had with the scales was getting the
readout head lined up.
One Sargon scale did have to have the pots tweaked inside the cable
plug end, on the little circut board. I don't suggest doing that unless
you have an Oscilloscope to troubleshoot with.
This was intended to show what is possible. WORST case scneario, you
need a new scale, but I doubt it. There are a lot of shops that do
scale repairs. I have a dealt with a shop in the Minneapolis are that
was able to get spare parts to fix scales with.
Thanks for responding. At this point I don't think it is the alignment.
Whether I tighten down the screws or not I get no change in the reading
when I move the slide. There doesn't seem to be a signal to the LEDs.
Ned Simm> >
With your description of careful handling, it's unlikely that any damage
occurred while you had it off.
It sounds as though a bad contact or connection might be the problem. The
little cover on the read head can be opened for inspection, but it should be
well sealed when replaced.
The cable conductors in the plug/connector end can be examined without the
risk of breaking any seal. You might also inspect the connector pins with a
magnifier to see that they are clean and bright. If you have a similar pin
of the same size, you can check that there is sufficient tension in the
mating connector contacts (with the power off).
Careful inspection of the cable might reveal a pinched spot or some other
sign that an individual conductor might've possibly been damaged.
With the scale connected and the display turned on, you might try rolling
the cable between your fingertips and thumb, while moving the cross slide,
to see if there might be an intermittent connection in the cable.
This could also be checked with an ohm meter with the head cover removed and
connector shell open, with the scale disconnected from the display.
The reader head should glide in the housing silently. Any noticable sound
could indicate an alignment problem. The basic design of the actual internal
pickup/reader device includes a wheeled trolley-of-sorts, that's intended to
keep the pickup device in alignment with the quartz/glass scale (without
Typical DRO scales aren't extremely complex, and can be disassembled fairly
easily for cleaning, by removing an end cap. If there happened to be some
loose debris in the housing, it may have found it's way onto the pickup
device when the scale was moved around during disassembly.
OK Ned, now I think I am getting it. My only other DRO experience was
installing and later repairing a Shooting Star 3 axis DRO on my mill. On
that, the alignment was pretty coarse. I presume that you are saying
that the alignment is very critical,and not a situation of binding, etc.
I originally removed the 4 screws (which hold the scale bar and sliding
component), noted where each of the mounting shims went and made no
adjustments. I then replaced everything exactly as removed. I then
turned on the DRO, zeroed it and everything stayed at zero when I moved
the slide. I then removed the screw from the sliding component and moved
it back and forth gently, the read out stayed at zero. So what you are
saying is that I must fine tune the total alignment? If so, about how
many thousandths alignment must be maintained?
The sliding component moves smoothly, so maybe I haven't broken anything
yet. Whether I tighten down the screws or not I get no change in the reading
I'm not sure what the details of construction of that Sargon scale are,
but if there is an
end cap that is screwed on, take one of them off and have a look inside.
is a glass scale glued into the aluminum beam. A small read head that
like a thick circuit board on each side of the glass scale will ride on
some sort of
arrangement. The expensive scales have the head rolling on micro-micro
The cheaper scales have the head riding on spring-loaded fingers with
mostly riding on the glass. With either design, it is not very hard
when handling the
scale loose from the machine to knock the head off the track. It will
obvious when you get a look inside if that has happened. Moving the
it is crooked is not a good thing, as it can damage the scale or the
analyzer grating in the
head, but that is not guaranteed. If the head is crooked, not close to
the glass, etc. it
should be fairly obvious which way you need to wiggle it to bring it
back onto the track.
You may be able to hold the flexible wiper material open with paper clip
wire or similar
improvisation to get a look at part of the head from a different angle.
These units usually
use a piece of music wire or a thin steel band to couple the internal
head to the external
slider part. Once the head is on the track, the wire or band may need
to be adjusted to
push/pull straight in the direction of travel, so it doesn't bow or push
the head at an angle.
Many units have a square pin-type connector of some sort, so the
external cable can be
disconnected from the head itself. If there is a bind-up or overtravel
when you reinstall
the scale, this plug could have pulled out. That would be the easiest
One other possible condition is that swarf got inside the scale, and had
to the ends by the head over time. You may have moved the head farther
when it was off the machine, and the head is now dirty and can't see the
scale. If you
are careful and used to handling tiny stuff, these scales are not that
hard to open
up and clean with alcohol and Q-tips. I did my Mitutoyo scales on my
was AMAZED at the amount of gunk that had gotten in there!
(This may be a duplicate)
I took everything apart today. Things looked good, no broken or loose
parts. There was surprisingly very little swarf or grime inside. Upon
inspection I found a broken orange wire. (Viola, I found it!) I repaired
the wire and put everything together and tried it out. No change. Still
registers 0.000" no matter the position. 8^(
I am interested in what you said about the bearings in the head. Mine
has 2 silver colored rollers. The spring, which is very stiff, holds the
head tightly to the base. It seemed to me that it should push in the
other direction toward the glass. I guess now I will try it and see what
As long as the read head is seated properly on the glass scale the alignment is
close enough for the scale to output pulses to the readout. How far you can be
off, and in which directions, and still have the scale work is a function of
the scale's overall design, but most of the scales I've worked with would read
if carefully hand guided. Jon described how the read head tracks on the glass,
and I agree with his suggestions re peeking inside to see what's going between
the read head and the glass.
The mounting requirements to maximize accuracy and minimize wear will be
fussier than what's required to simply get the thing working.
It's helpful to understand that the read head doesn't pick up every line on the
scale. The read head also carries a short grating similar to the main scale and
the detector on the read head is looking at the interference pattern that
results as the two gratings move relative to one another.
It may be helpful to post a photo of the scales as someone may be able to ID
the manufacturer. It's my impression that there are more DRO manufacturers than
scale mfrs and it's possible the scale mfr is still around even though Sargon
Well, be careful. But, the sensing part of the head should be
REALLY close to the side of the glass that has the silver grating
deposited on it. The lamp side of the head is often fairly far
away, so the beam is pretty parallel.
But, make sure the glass analyzer grating on the head doesn't
scrape the silvering (usually tungsten or nichrome, actually)
off the glass. There needs to be something that keeps the two
glass parts from crashing into each other. If the analyzer
grating is more than a mm away from the scale, that is definitely
the problem. A kink or misalignment of the coupling wire could
definitely shove the head the wrong way. The rollers could
ride directly on the glass, or on the housing. Usually, they
have MORE than just 2 rollers. I've seen some with 8, 4 on the
glass and 4 on the housing, and some other combinations. There
is usually also something to keep the head from twisting on the
scale, as it has to stay parallel to the sliding direction for
the tiny slots in the analyzer to stay parallel to the ones in
the scale. (There are also Moire scales that depend on a precise
tilt between the read head and scale. I hope you don't have one
Anyway, the analyzer glass should be something like .010 to .015"
at most away from the scale.
I think, from your description, that the read head is now in the wrong
position. What I think is happening is that the head is now on the
wrong SIDE of the scale. The head should be held close to or touching
the scale. The spring should be on the OTHER SIDE of the scale that
the head is on. You are right (I think) in surmising that the spring
should hold the head against the scale, not away from it. If the read
head is pulled off the scale you may not know it because the rubber
flaps add enough drag that the head slipping off isn't noticed. It's
been a while since I took one of these apart to fix it but that's the
way mine worked as I recall.
Thanks again Ned. I just submitted some pictures to the dropbox under
Jays DRO. On further investigation I think I have a broken LED (?) At
least one of 8 somethings appears to have been broken. There are 4 of
them across from each other on the opposing boards. I couldn't get the
pictures up close enough to show the break.
For the life of me, I don't see how I could have broken the wire or the
component in question. I cannot believe how delicate this thing is. I
found someone on Net that has a scale he wants $200 for, but I sure
would hate to buy a bad scale. Not much recourse
Ned Simm> >
According to JayCups :
Your camera *has* a macro mode -- you simply need to learn how
to turn it on. Here is part of the information from the EXIF data in
your photos -- since you posted the whole image without cropping (which
would have reduced the size significantly):
File Name : Jays_DRO_2.jpg
File Size : 208KB
File Type : JPEG
Image Description : OLYMPUS DIGITAL CAMERA
Make : OLYMPUS OPTICAL CO.,LTD
Camera Model Name : C920Z,D450Z
Orientation : Horizontal (normal)
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Software : v873-75
[ ... ]
Special Mode : Normal, Sequence: 0, Panorama: (none)
Image Quality : SHQ
Macro : Off For the life of me, I don't see how I could have broken the wire or the
Did you remove the read head before the problem occurred? They
are normally fairly well protected while fully assembled.
Granted -- if you tilt it to nearly vertical, and let the read
head slide down to the end stops, it may well hit something which will
break some part of the read head. Ideally, I would have put a cable tie
around the spar of the scale and the armored wire to keep the head from
sliding around loose while the scale was off the machine.
If it is shipped tied down as I suggested, it should be fine, if
it was fine when he shipped it.
You might want to send the entire scale (cable and all), out for repair and
It's not really a DIY job, since the replacement components need to match
the specs of the original parts, and it's highly unlikely that a complete
parts list and calibration procedure is available. I believe the light
emitters are infrared, for example.
If you have the Sargon model literature, including the scale specs,
resolution and cable pinouts for the signals and power connections, you
could select a suitable replacement scale of another brand, such as Anilam,
Acu-Rite or similar 5 volt TTL scale.
Without unreasonably high expectations, you might be able to find a good
replacement scale, or a NOS reader head on eBay, if you'd be willing to
chance getting a working unit from a trustworthy source. I've bought
numerous good DRO components on eBay, in new or good working condition.
The short (lathe cross slide) and the mini-scales will generally cost as
much as a long scale because they're compact, and fit places that full-sized
I found a scale that will work for a pretty reasonable price on the Net.
It seems that every time I took the damn thing apart I found something
else wrong with it. I don't know if I am doing the breaking or it was
just about to fall apart and my timing is bad. But my lathe has been
down for days and I need to get it up to speed so getting a good scale
for a reasonable price seems more cost effective than spending the next
week up tuning up my poor electronics skills.
The glass is glued to the aluminum extrusion and there is no way to see
if the silver grating is still in place.
Hopefully the new one will work out of the box.
Thanks to everyone for your help.
The scale is not able to fall off the glass so you know it's still
there. Some scales use IR LEDs. To see if they are working a digital
camera or a CCD video camera will usually show if they are on or not.
I tested my digital camera, video camera, and a web cam by shining a
remote control at them. All showed the flashing LED on the remote. I
know that the way the readers work is by seeing the IR light shining
through the glass and detecting the shadows from the scale that is
either etched and plated or just plated onto the glass. There should
be two light recievers. They are slightly out of phase with each other
so that when one detects a line the other can't see it. This way the
read head can read the leading edges and trailing edges from each
scale line twice. This means 4 counts per line are possible. I do have
an old encoder that works exactly like the modern ones except that it
uses a tiny light bulb instead of LEDs and another that uses visible
LEDs but I'm pretty sure that all modern ones use IR LEDs.