PDF 8200 DRO Instructions

PDF 8200 DRO Instructions
An optional third handwheel and
encoder unit can be used on the
vertical milling column to turn
your lathe into a vertical milling
machine with a 3-axis digital
The Digital Readout in the Modern Machine Shop
Digital readouts are popular on full size machine tools
because they make the life of a machinist much simpler. They
make it easier to accurately set or change the table position
and eliminate errors caused by misreading handwheel
increments or losing track of multiple rotations. Now that
same convenience is available on tabletop size machines
with the availability of a D.R.O. (Digital ReadOut) for
Sherline lathes and mills. The compact electronics package
and clever backlash compensation feature were designed
by John Wettroth.
On industrial DRO’s, a sensor reads a highly accurate
external scale. On Sherline’s DRO, the sensor reads rotation
of the leadscrew. Because of the accuracy of Sherline’s
precision rolled leadscrew threads and the short travels
on a machine of this size, this system makes it possible to
provide a DRO with sufficient accuracy while maintaining
a price appropriate for a machine of this size and cost.
The kit can be installed on any Sherline lathe, regardless
of age and is very easy to use. Three axes of movement are
provided so the readout can be used when the lathe is set
up as a mill with the vertical milling column attachment.
In the lathe configuration you will use only two of the
three, as the tailstock spindle feed screw is not fitted with
a readout. Remember that the directions of movement of
the mill are referred to as the X-axis (table side-to-side),
The designations of the axes of movement are
different in lathe and mill configurations. A lathe
used with a vertical milling column is considered
a mill when it comes to naming the axes.
Lathe Digital Readout
P/N 8200 (Metric P/N 8260)
Y-axis (table in-out) and Z-axis (spindle up-down) when
seen from the leadscrew handwheel end of the lathe. When
used as a lathe, the nomenclature changes slightly. The
crosslide feed handwheel still controls what is called the
“X” axis, but the leadscrew controls what is now called the
“Z” axis. Remember also that as you feed the cutter into the
rotating part with the crosslide handwheel you will reduce
the diameter of the part by twice the amount of the feed. This
is because you are reducing the part's radius but measuring
its diameter. This DRO measures the change in radius.
The readout of any axis can be set to zero at any time with
the push of a button. As you move the handwheels you can
read the table position to three and a half decimal places on
the digital readout. It is not necessary to keep track of the
number of handwheel rotations to figure the stopping point on
larger dimensions. This will be especially appreciated when
cranking in “negative” amounts. Backlash is compensated for
by setting it into the unit’s electronic memory in increments
of .0005". As a bonus, the package also includes an electronic
readout of spindle RPM at all times.
Installing the D.R.O. Components on your Sherline Lathe
The following instructions describe the steps required to
remove the existing handwheels and thrust collars and
replace them with the D.R.O. encoder/handwheel units.
1. Move the crosslide all the way in. This will help locate
the slide screw to assure that the collar is centered. The
saddle can be positioned anywhere on the leadscrew.
2. If using a vertical milling column, raise the headstock
all the way up to the top of its travel
3. Using a 3/32" hex wrench, remove the existing
handwheels from the crosslide, leadscrew and vertical
milling column by releasing their set screws and sliding
them off their leadscrews. (If your lathe has resettable
“zero” handwheels, loosen the collar locking knob
and rotate the collar until the hole lines up with the set
screw. Then use the 3/32" hex wrench to loosen the set
screw and remove the entire handwheel/collar unit.)
SHERLINE PRODUCTS INC. • 3235 Executive Ridge • Vista • California 92081-8527 • FAX: (760) 727-7857
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FIGURE 1A—Installing
the new thrust collar on the
crosslide screw.
FIGURE 1B—Installing
the new thrust collar on the
FIGURE 3—Detail of the encoder housing showing direction
of installation
of the leadscrew. On the leadscrew, hold the table (not
the base) with one hand and push the handwheel onto
the shaft with the other. Rotate the handwheel so that
the set screw tightens on a new part of the shaft. If you
don't, it will tend to pick up it's old indentation making
it difficult to tighten it in a new position.
See Figure 3 for orientation of the encoder housing. The
thicker shoulder inside the encoder should be facing
toward the thrust collar. It is easier to tighten the screws if
you install the units upside down with the screws coming
down from the top. Place the two halves of the shell over
the thrust collar and over the encoder ring and install the
four #2 x 3/8" self-tapping screws. Draw the screws down
4. Using a 3/32" hex wrench, remove the 5-40 screw
holding the thrust collar over the crosslide and remove
the collar. (See Figure 1A.) Use a 1/8" hex wrench to
remove the countersunk screw in the top of the lathe
bed and a 5/32" hex wrench to remove the socket head
cap screw under the lathe base so that the collar can be
removed from the leadscrew. (See Figure 1B.)
5. Clean each grooved thrust collar with a solvent like
acetone or lacquer thinner to remove any oil from the
surface. (You will later lock them in place in relation
to the plastic housing with “instant glue” and it will
not stick to an oily collar.) Using the existing screws,
install new grooved thrust collars on the X- and
Y-axes, making sure the leadscrew is centered in the
collar. Make sure the screws are secure, but do not
overtighten. If a shim washer was present on your
existing leadscrew, reinstall it as it was before.
6. Install a new handwheel with encoder ring on
the crosslide screw and leadscrew. Note that the
handwheels are similar except on the leadscrew,
the numbers face away from the handwheel. On the
crosslide they face toward the handwheel. Make sure
the shoulder at the end of the leadscrew thread is seated
against the thrust collar and the handwheel is pushed
in tightly to remove end play before tightening the set
screw. On the crosslide, push the crosslide table toward
the bed so that the collar is securely against the shoulder
FIGURE 2—Making sure the crosslide screw is centered
FIGURE 4—Installing the encoder unit over the thrust collar.
The unit can be installed upside down to make it easier to put
in the screws. It is then rotated into position and tightened to
lock it in place.
1. First the shell is installed over the thrust
collar and handwheel upside down. (Left)
2. Then the shell is rotated into position
with the cable lead on the bottom. (Below)
FIGURE 5—Rotating the unit into its proper position. (Note:
Handwheel/encoder unit not shown for clarity.)
P/N 8200, Pg. 2 OF 6
until they seat snugly, but DO NOT OVERTIGHTEN or
you will strip the threads! Once tightened into position, the
unit can be rotated around until the screws and cable are
on the bottom. When finished, the cable from the encoders
should come off to the right side of the handwheel.
FIGURE 6—On the long bed lathe, the leadscrew handwheel
sensor housing must be positioned as shown.
FIGURE 7—Order of
washers and bearing
in Z-axis thrust collar
for optional vertical
milling column.
P/N 8135
Leadscrew Handwheel Position on the Model 4400 Lathe
The die cast base on the Model 4400/4410 long bed lathe
is relieved so that the bed and base align. The lip on the
bottom of the machined area will keep the sensor housing
from being able to be rotated straight down. The solution to
this is to orient the housing as shown in Figure 6 above. The
joint between the two halves of the housing now becomes
the witness mark against which you read the handwheel
markings. On the Model 4400/4410 lathe, the bed and
base are flush at the end, so the housing can be positioned
straight down as is shown in the other figures.
Making Sure the Housings do not Move
The sensors that read gear-tooth position as you turn the
handwheel are located in the bottom of the handwheel
housing. If the housing moves, it is the same as if you
moved the handwheel, because it changes the relationship
between the sensor and the gear tooth. Therefore, the
housing should be anchored in place so that it cannot be
inadvertently moved. The screws that hold the two halves
together go into plastic, and overtightening them can strip
the threads out of the hole. If the housing rotates too easily
when the screws are tightened, you can remove the housing
shell and sand the mating surfaces on a piece of sandpaper
on a flat surface until they grip the collar more tightly. If
this doesn't do the job, another solution is to place a drop
of “super glue” between the plastic housing and the metal
collar once the housing is positioned where you want it.
This will keep it in place but can still be broken loose if
you need to later.
hex wrench, remove the flat head screw that holds
the Z-axis thrust collar to the vertical milling column.
Remove the collar by lifting it up and off the leadscrew.
If the spacer washer sticks to the bottom of it, remove
it and reinstall it on the leadscrew shaft. Then remove
the ball bearing thrust and two washers from the collar
and reinstall them in the new Z-axis thrust collar in the
same order. (See Figure 7.) Install the new collar on
the leadscrew shaft and secure it to the bed with the
flat head screw.
Install the remaining handwheel and encoder unit onto
the vertical milling column leadscrew. Lift up on the
saddle assembly until the washer and shoulder of the
leadscrew are all the way up against the bottom of the
collar. Then push down on the handwheel and tighten
its set screw, being sure to tighten it against a new
spot on the shaft. Install the pickup housing over the
handwheel unit as shown in Figures 4 and 5. When
finished, the cable should exit toward the left when
viewed from the front.
Installing the RPM Sensor
Reinstall the headstock/motor/speed control onto the
lathe or milling column.
Peel off the backing and apply the 2-1/2" round sticker
to the pulley. (HINT: A little liquid window cleaner
on the pulley allows the sticker to be repositioned and
bubbles squeezed out before it adheres. Once the liquid
is squeezed out and dries, the adhesive on the sticker
will stick fine.)
Locate the RPM sensor by holding it in the position
shown in Figure 7. Mark the center of the hole on the
plastic belt housing and drill a 1/16" hole. Fasten the
sensor to the belt housing using the self-tapping screw
provided. (Do not overtighten or you can strip the
threads.) A plastic tie-wrap is provided to secure the
sensor lead to the motor’s power cord to keep it out of
the way.
P/N 8200, Pg. 3 OF 6
Drill 1/16" hole and mount
sensor head using the selftapping screw provided.
FIGURE 8—Mounting the sensor to the belt housing in the mill
configuration. The mounting position would be the same in the
lathe configuration.
NOTE: If you have a lathe with an older AC/DC motor that
does not have a plastic belt guard, the RPM sensor can be
mounted in the proper position over the pulley by attaching
it to the motor mounting bracket. Locate and mark where
the hole should be drilled. Remove the motor and drill a
hole through the bracket. You can use a self-tapping sheet
metal screw or a bolt and nut through the hole, or you can
tap the hole to match the thread of the bolt you use.
Hooking Up the Connecting Cables
Plug the cable connector from each encoder unit into its
respective port on the display unit. The telephone type cable
connectors go in with the locking tab facing up when the
unit is lying on its back. The RPM sensor cable goes into
the port marked “Tach In”.
Plug the power adapter into the bottom hole marked “DC
In”, and plug the transformer into a 115 VAC (60 Hz.)
source. Check to make sure all three axes are functioning.
Turn on the motor and check to see that the RPM indicator
is functioning.
Initializing Your Display for Inch or Metric Leadscrews
When you press the “Power” button to turn your system
on, the upper right corner of the display will read either
“inch” or “metric” mode. Normally, the DRO will be
set up properly when you receive it, but there is always
a possibility it could be set wrong. To set or change the
system of measurement your unit displays, follow these
1. With the power off, unplug the power cable from the
display unit.
2. INCH—Hold down both the “Power” button and the
X-axis button while you plug the power cord back into
the display unit. After the display comes up, release
the buttons. The display should now read in inch
3. METRIC—To initialize your display unit to read metric
dimensions, hold down the “Power” and “Y” buttons
while plugging the power cord back into the display
unit. Once initialized, the unit will always read in your
chosen system of measurement each time it is turned
on unless you change it.
The DRO reads rotary handwheel movement and
converts it to a linear dimension based on a formula
assuming a certain leadscrew thread pitch. The DRO
must be set to agree with the leadscrews installed
on your machine to provide accurate measurements.
The only difference between the inch and metric packages
is the number of divisions engraved into the handwheels.
The electronics package is the same for either and can be
set to read in either measurement system depending on the
leadscrews of the machine on which it is installed.
Setting the Backlash Compensation Values
To set backlash compensation for each axis, you must
first measure to determine what the backlash is. Use a dial
indicator to determine how far the handwheel on each axis
rotates before the table starts to move. (If this amount is
excessive, see your instruction manual for instructions on
setting backlash. It should ideally be in the .003" to .005"
range.) Once the amount is determined, the backlash is
compensated for by setting it into the display unit’s memory.
To set the backlash to correspond to your machine's
leadscrews, complete the following steps for each axis:
1 Turn the handwheel for each axis one full turn
clockwise. This assures that the software starts the
backlash compensation at the proper initial point.
2. Hold down the “Power” button for longer than a second
until the display changes.
3. Now you can set in the backlash for each axis by
pushing the button for that axis. Each time the button
is depressed, .0005" (or .01 mm on metric units) is
added to the reading. Set in the amount of backlash
you measured previously for each axis. Amounts up
to .015" (.50 mm) can be set. (Note: You cannot cycle
backwards to a lower number. If you go past your
desired setting you must continue pushing the button
until the reading passes .015" (.50 mm) and returns to
zero. Then start over.)
4. Once the backlash for all three axes is set, briefly push
the “Power” button again to return the display to its
normal reading. The backlash setting can be checked
or changed at any time by holding the power button
until the display changes. The amount can then be reset
as described in instruction number 3 above. Once set,
backlash settings are held in a special memory chip
even if the unit is turned off and unplugged. They
remain until you change them.
P/N 8200, Pg. 4 OF 6
Using the DRO with the Sherline Power Feed
or Thread Cutting Attachment
The DRO leadscrew thrust collar is longer than the standard
thrust collar so that the DRO housing can attach to it. This
changes the position of the leadscrew. This has no effect
on the lathe except when it is used with a power feed or
thread cutting attachment. In those cases you will need to
replace the existing sliding engagement shaft (P/N 1509)
which will be a little too short. If you return the existing
shaft to Sherline it will be replaced at no charge with a
shaft of the appropriate length (P/N 81509) for use with the
DRO. If you purchase a new power feed or thread cutting
attachment, notify Sherline that you will be using it with
the lathe DRO and the proper shaft will be supplied with
your purchase. The only alternative to solving this problem
would have been to provide a longer leadscrew which
would have been far more expensive.
Adjusting the Z-Axis Handwheel Screw
To adjust tension on the screw, first remove all Z-axis
backlash in the conventional manner by lifting the motor/
speed control unit by hand while tightening the handwheel
set screw on a “fresh” quadrant of the leadscrew to avoid
picking up any previous indentations. Once adjusted, tighten
the new center screw only until it is “finger tight”. Use a
very small amount of Loctite® on the end of the screw to
keep it in place. (Do not coat the threads or the screw may
become impossible to remove.) Overtightening the screw
will cause the handwheel to become hard to turn. The
purpose of the screw is not to adjust backlash, but rather
to keep it from increasing once it is properly adjusted. Do
not try to use the screw to pull out additional backlash.
The small 5-40 threads are not strong enough for this task.
A Few More Tips
When in use, shield the unit from chips so they don't
accumulate around the telephone jack connections
Getting the Most Out of Your DRO
When using a machine equipped with a digital readout, we
find it is best to use either the readout or the handwheels,
but not both. If the displayed accuracy of .0005" (.01mm)
is satisfactory for the job you are doing, use just the digital
readout and disregard the handwheel settings. In cases
where you might want to interpolate to a higher degree
of accuracy, the markings on the handwheels will allow
you to do this.
An example of this would be where you have located the
center of a bored hole and then changed the table position.
To return the spindle exactly to the hole's center again using
the digital readout could leave you a few ten-thousandths
off, which may not be acceptable. In this case, you should
write down your handwheel settings and direction the
handwheel was last turned before moving from the desired
location. This will allow you to return to the same spot
with great accuracy. The handwheel marks are .001" or
.01mm apart. By reading the space between the marks on
the handwheel and interpolating your position, you can
achieve a high degree of accuracy. Knowing your machine
is an important part of achieving this kind of accuracy, and
as you get more familiar with your machine, your accuracy
will continue to improve.
Sherline's DRO brings modern machine shop technology
down to tabletop size and makes your Sherline tools easier
and more fun to use. we think you will find the digital
readout to be a great addition to your Sherline machine shop.
Thank you,
Sherline Products Inc.
on the side. Do not use an air hose to clean the unit.
A metal stand is now included with your DRO so you can
stand the unit up on your workbench. This makes it easier
to read while you work. If you wish to secure the box to the
stand, a piece of double-sided foam tape is a good method.
P/N 8200, Pg. 5 OF 6
P/N 8200 Digital Readout
Exploded View and Parts Listing
(Mill Z-axis)
NOTE: Numbered items are complete parts or assemblies. Part
reference numbers shown within the assemblies are individual
components that make up the assembly. Some are not for sale
individually and do not have part numbers listed.
Mill DRO box and electronics (complete)
Crosslide handwheel, inch (Met. 81322)
Leadscrew handwheel, inch (Met. 81332)
Encoder housing w/ wheel and cable
Encoder housing upper cap
Encoder housing body
Encoder housing lower cap
Crosslide thrust collar
Leadscrew thrust collar
#2 x 3/8” Self-tapping pan head screw
sensor housing
*Assembly includes housing,
sensors and cable and screws but
not handwheel and gear.
2-56 x 3/8" pan head Phillips screw
Tachometer encoder & cable asby.
Tachometer pickup decal
#2 x 1/4” Self-tapping pan head screw
Encoder star gear
Black tie-wrap (not shown)
115 VAC Power supply/transformer (not shown)
Stand for readout display box (not shown)
Z-axis support screw (not shown)
P/N 8200, Pg. 6 OF 6
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