SERVICE MANUAL
TABLE OF
CONTENTS
I Introduction 2
II Assembly of a standard ballnut 3
III Mounting of a standard ballnut 4
IV Instruction for preload installation 5
V Setting the preload ballnut 6-7
VI Lubrication 8
VII Bellows & Wipers 9
VIII Bearing Mounts 10-13
IX Troubleshooting 14
X Retrofit for Bridgeport Series 1 Mills 15-17
XI Contact Information 18
I. INTRODUCTION
This service manual was prepared to insure proper
installation and performance of the RBS ball screw
assembly throughout the life of the screw. It is only
meant as a convenient reference and not a complete
guide of the topics within.
The products shown in this catalog are intended
for industrial use only and should not be used
to lift, support or otherwise transport people,
unless you obtain a written authorization for each
individual application from Rockford Ball Screw Co.
The specifications and data in this publication are
believed to be accurate and reliable. However, it is
the responsibility of the product user to determine
the suitability of Rockford Ball Screw products for a
specific application.
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II. ASSEMBLY OF A STANDARD BALLNUT
1 Remove the return tube clamp and the return tube
from the ballnut.
2 Place the nut mid-way on the screw and align the
ball grooves in the nut with those on the screw.
3 Place a short length of rod or dowel into one return
tube hole to prevent loss of balls.
4 Place balls successively into the other return tube
hole, rotating the screw so that the balls are fed
along the thread and through the nut until the ball
circuit is completely full.
5 Remove rod or dowel, being careful not to rotate the
nut. The balls must not be in the return tube holes.
Balls should only be in the mesh between the ball
nut and screw.
6 On both ends of the return tube, place a small
amount of light grease.
7 Load this half tube full of balls.
8 Place the second half of the return tube over the
balls and hold the two halves tightly together.
9 Place the return tube ends into the ball circuit holes
in the nut (the grease in the tube holes will prevent
the balls from dropping out).
10 Place the tube clamp over the tube (taking care to
keep the two halves together) and secure with the
clamp screws.
CLAMP SCREWS
TUBE CLAMP
RETURN TUBE LOADED
WITH BALLS
A
PPLY GREASE HERE
BALLNUT
FIGURE 1
BALLNUT ASSEMBLY
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III. MOUNTING OF A STANDARD BALLNUT
1 Remove the tie from the ballnut/arbor assembly.
2 Butt the assembly onto the end of the screw while
continuously holding the arbor (cardboard tube)
steady. Align the bottom of the return tube with the
beginning of the first thread. Do not allow arbor to
come out of contact with screw thread. Failure to do
so could result in the loss of balls from within the
assembly. (See figure 2).
3 If you find that the arbor does not fit up to the
beginning of the thread due to interference from
the journal, (See figure 3).Then it is recommended
that the journal be wrapped in masking tape or
something similar so that the journal OD equals that
of the arbor. This in effect would act as an extension
to the arbor and would fill the same role.
4 Then gently rotate and apply pressure onto the
nut to mount the nut. The arbor should only lose
contact with the end of the screw when the ballnut
is engaged on the screw.
(Not a preload nut or Bridgeport nut)
A
RBOR
BOTTOM OF RETURN
TUBE LINED UP WITH
START OF THREAD
FIGURE 2
MOUNTING ALIGNMENT
JOURNAL
ARBOR
FIGURE 3
JOURNAL INTERFERENCE
A
RBOR
BOTTOM OF RETURN
TUBE LINED UP WITH
START OF THREAD
FIGURE 2
MOUNTING ALIGNMENT
JOURNAL
ARBOR
FIGURE 3
JOURNAL INTERFERENCE
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IV. INSTRUCTION FOR PRELOAD INSTALLATION
1 Remove the tie that is through the arbor, being
careful not to let the arbor sliding out from within
the assembly.
2 Align the nut assembly to appear like drawing
figure 4.
3 The tangs of the coupler are to be aligned so as to
mate with the ballnuts. An external preload coupler
needs to engage the roll pins to prevent rotation.
4 Transfer the assembly to the screw with some
downward pressure till the threads are engaged
then roll the nut on. Be sure to hold the arbor while
transferring the screw. The arbor should not come
out of contact with the screw until the nuts are fully
engaged. The preload nut is now ready to be set.
BACK BALLNUT
COLLAR
PRELOAD
COUPLER
WAVY
SPRINGS
FRONT BALLNUT
SQUARE NUTS
FRONT BALLNUT
BELLVILLE
SPRINGS
PRELOAD
COUPLER
COLLARBACK BALLNUT
ROUND NUTS
FIGURE 4
DISSASSEMBLED PRELOAD
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1 Remove the setscrews in the adjusting collar.
2 2. With a spanner wrench (see table 1), tighten the
collar until the desired load is achieved (see table 2,
page 7).
3 3. Put the set screws back in and tighten the set
screws in order to not let the adjusting collar back
off. It is preferred not to tighten the setscrews on the
tang section of the coupler.
Note:
Setting the preload increases the torque on screw by .034 x preload setting x lead of screw.
TABLE 1: SPANNER WRENCH SIZING
MODEL # SPANNER WRENCH HOLE SIZE
RP-10 to RP-16 1/8"
RP-20 to RP-46 3/16"
RP-50 to RP-58 1/4"
RP-60 to RP-74 3/8"
RP-80 1/2"
V. SETTING THE PRELOAD BALLNUT
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V. SETTING THE PRELOAD BALLNUT - CONTINUED
Note: Due to spring load tolerances, these figures are ±20%, use the number of turns as a guide only.
TABLE 2: PRELOAD SETTINGS
MODEL NO.
RECOMMENDED MAXIMUM
PRELOAD (LB) # OF TURNS PRELOAD (LB) # OF TURNS
RP10 15 0.10 45 0.30
RP11 30 0.20 90 0.50
RP12 17 0.10 51 0.30
RP15 3 0.03 8 0.05
RP16 5 0.03 15 0.10
RP20 85 0.10 255 0.30
RP21 14 0.05 42 0.20
RP30/31 83 1.25 248 1.50
RP30A/31A 165 1.25 495 1.50
RP32 17 0.30 51 0.90
RP34/34A 190 0.30 570 1.0 0
RP35/35A 95 0.20 285 0.50
RP36 16 0.05 48 0.10
RP37 340 0.60 1020 1.25
RP38 60 0.10 180 0.30
RP40/41 163 0.10 488 0.30
RP40A/40AR/40RF/41LF 325 0.20 975 0.60
RP40B 450 0.30 1350 0.80
RP42 345 0.20 1035 0.60
RP43 425 0.40 1275 1. 10
RP44 230 0.20 690 0.40
RP45/47 245 0.20 735 0.50
BRP45/47 145 0.10 435 0.30
RP46 49 0.05 147 0.10
RP48 330 0.20 990 0.60
RP50 905 0.60 2715 1.80
RP50A/51A 1290 1.20 3870 3.20
RP53/54 425 0.80 1275 2.00
RP53A/54A 640 1.30 1920 2.00
RP55/56 800 0.50 2400 1.70
RP57 1005 0.60 3015 2.00
RP58/58A 735 0.50 2205 1.60
RP60/63 1980 1.20 5940 2.00
RP60A 2970 1.80 8910 2.10
RP61 2250 0.40 6750 1.20
RP62 1800 0.30 5400 1.00
RP70 2200 1.20 6600 2.80
RP71 2650 1.50 7950 2.80
RP74 630 0.80 1890 2.00
RP75 3250 0.60 9750 1.90
RP80/80A/81A 4200 1.80 12600 3.20
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VI. LUBRICATION
Apply lubrication between the ball & raceway to avoid
friction failure, deformation, and the shortening of life
of the ball screw. It is only necessary to prevent the ball
nut assembly from becoming dry. Lubrication should be
applied on the surface of the shaft or through the fitting
into the nut. A 90% reduction in ball bearing screw life
should be allowed where dry operation is unavoidable.
At speeds greater than 200 in/min it is recommended
oil be used. Grease can be used for speeds below 200
in/min. In the event that oil or grease is not an option,
dry film lubrication is recommended. Surfaces should
be phosphate coated before being coated with dry film
lubrication.
For a list of acceptable lubricants see table 3.
Note:
For general application use, the range of NLGI 2-3 of lithium base grease
or the range of 46-100 CST at 40 ºC of oil is recommended. Graphite
based lubricants are not recommended due to their abrasive qualities.
TABLE 3: ACCEPTABLE LUBRICANTS
LUBRICANT BRAND NAME MANUFACTURER
Grease
Alvania No. 2
Mobilux No. 2
Beacon 2
Shell
Mobil
Esso
Oil
Tellus 33
D.T.E. Heavy Medium
Teresso 52
Shell
Mobil
Esso
Dry Film
Dow Corning 321
Perma-Silk
Dow Corning
EM Corporation
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VII. BELLOWS AND WIPERS
Conditions for Wipers, Wiper Installation
Wipers are recommended in any conditions where the
ball nut and/or screws are exposed to debris.
Slide two wipers into the ballnut along the screw. Make
sure the brush and wiper is held entirely within the nut.
Push the snap ring into the snap ring groove just inside
the nut. Repeat this process for the other side.
Installation of ballnut onto the screw would be made
more difficult if wipers are already installed in the ballnut.
If you prefer the wiper could be temporarily removed to
ease installation. However, it is not possible to remove
wipers that have been installed in the nut with epoxy.
Bellows
Bellows (or boot) should be considered when a wiper
is unable to adequately prevent the entry of debris into
the nut. Here is a list of manufactures to consider when
ordering a bellows.
Dynatech
Manufacturing
2300 S Calhoun Rd
New Berlin, WI 53151
phone: (262) 317-919
fax: (262) 786-3280
Heeco Protekto Boots
P.O. Box 9279
Tampa, FL 33674
phone: (813)886-7584
fax: (813) 885-2350
Hennig Inc
9900 N Alpine RD
Machesney Park, IL 61115
phone: (815) 636-9900
fax: (815) 636-9737
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VIII. BEARING MOUNTS
BM Series Bearing Mounts are SIMPLE supports that
utilize a set of angular contact ball bearings mounted back
to back. These bearing mounts are designed to support
radial and axial load components of force. (see page 11)
BMF Series Bearing Mounts are FIXED RIGID
supports that utilize a set of spaced angular contact ball
bearings. These bearing mounts are designed to support
radial and axial load components of force. (see page 12)
BMR Series Bearing Mounts are SIMPLE RADIAL
supports utilizing shielded radial ball bearings for
supporting radial load components. These bearing
mounts are NOT intended to support axial load
components of force. (see page 13)
REAR
FRONT
BM BEARING BLOCK
FRONT
BMF BEARING BLOCK
REAR
FRONT
REAR
BMR BEARING BLOCK
FIGURE 5
BEARING MOUNT
Note:
1 A tubular arbor should be made from aluminum to prevent damage to the journal and bearings. The arbor’s OD
is to be the same diameter as rear ring seal and ID to have clearance on journal.
2 Do not over tighten the bearings, this will increase the drag torque and shorten the life of the bearings.
3 Rockford Ball Screw is not responsible for damage or personal injury due to incorrect assembly, sizing or
mounting of R/B/S bearing block assemblies.
TABLE 4: LOCKNUT TORQUE TABLE FOR BEARING MOUNT MODEL #BM/BMF/BMR
Bearing Size 10 12 15 20 25 30 45
Torque (FT-LB)
10-20 10-20 10-20 12-35 23-50 32-60 32-60
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VIII. BEARING MOUNTS - CONTINUED
1 Install the entire block either horizontal or vertical
onto the journal of the screw until the bearings and
front ring seal are seated against the shoulder of the
ball screw's journal.
2 Next, install rear ring seal, locknut and lock washer;
torque the locknut to the proper setting (See table 4,
page 10 for recommended torque).
3 Tighten the four button head cap screws until there
is no axial or radial play in the bearing block, this will
cause a slight increase in drag of the bearings.
BM Bearing Series Installation Instructions
BEARING PLATE
ANGULAR CONTACT BEARINGSANGULAR CONTACT BEARINGS
OIL SEAL
OIL SEAL
FRONT RING SEAL
REAR RING SEAL
LOCK WASHER
LOCKNUT
BUTTON HEAD CAP SCREWS
BALL SCREW JOURNAL
WILL ENTER BM BLOCK
FROM THIS DIRECTION
FIGURE 6
BM BEARING BLOCK
BEARING BLOCK
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1 Install the entire block either horizontal or vertical
onto the journal of the screw until the bearings and
front ring seal are seated against the shoulder of the
ball screw’s journal.
2 Next, install rear ring seal, locknut and lock washer;
torque the locknut to the proper setting (See table 4,
page 10 for recommended torque).
3 Tighten the four button head cap screws until there
is no axial or radial play in the bearing block, this will
cause a slight increase in drag of the bearings.
BEARING PLATE
ANGULAR CONTACT BEARINGSANGULAR CONTACT BEARINGS
OIL SEAL
OIL SEAL
FRONT RING SEAL
REAR RING SEAL
LOCK WASHER
LOCKNUT
BUTTON HEAD CAP SCREWS
BALL SCREW JOURNAL
WILL ENTER BM BLOCK
FROM THIS DIRECTION
FIGURE 7
BMF BEARING BLOCK
BEARING BLOCK
INNER BEARING SPACER
OUTER BEARING SPACER
BMF Bearing Series Installation Instructions
VIII. BEARING MOUNTS - CONTINUED
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1 Install the entire block either horizontal or vertical onto
the journal of the screw until the bearing is seated
against the shoulder of the ball screw’s journal.
2 Next, install locknut and lock washer; torque the
locknut to the proper setting (See table 4, page 10 for
recommended torque).
BEARING PLAT
E
RADIAL BALL BEARING
LOCK WASHER
LOCKNUT
BUTTON HEAD CAP SCREWS
BALL SCREW JOURNAL
WILL ENTER BM BLOCK
FROM THIS DIRECTION
FIGURE 8
BMR BEARING BLOCK
BEARING BLOCK
BMR Bearing Series Installation Instructions
VIII. BEARING MOUNTS - CONTINUED
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IX. TROUBLESHOOTING
BALLSCREW WOBBLES/VIBRATES
DURING OPERATION:
1 Inspect mounts; check to make sure ballnut and end
supports are tight and properly aligned.
2 Check critical speed and column loading per R/B/S
catalog. Do not exceed the safe critical speed or
column loading as stated in the catalog.
3 Check straightness of screw.
4 Consult Factory.
BALLSCREW MAKING EXCESSIVE NOISE:
1 Make sure adequate and proper lubrication is present
on screw.
2 Check for excessive debris on screw or in nut.
3 Check alignment and mounting areas for adequate
rigidity. Be sure to inspect for moment (cocking)
loading on the nut. This could cause ball binding and
reduction in life.
4 Consult factory.
EXCESSIVE BACKLASH IN SYSTEM:
1 Inspect mounting areas for tight assembly.
2 Inspect support bearing backlash to determine if
backlash is coming from bearings.
3 If preloaded ballnut assembly, tighten per pages 6 &
7 in this manual.
4 Consult factory.
BALLNUT DRIFTING (BACK-DRIVING)
UNDER LOAD:
1 Install motor brake to hold load. Consult catalog to
determine torque required.
2 Consult factory (a screw with a finer lead may be
required).
BALLSCREW EXPERIENCING
PREMATURE FAILURE:
1 Premature failure may be caused by many reasons
such as, lack of lubrication, misalignment, metal
chips or other debris, over loading of screw and
excessive speed.
2 Consult R/B/S catalog or WEB Site.
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X. RETROFIT FOR BRIDGEPORT SERIES 1 MILLS
ASSEMBLY INSTRUCTIONS: RETROFIT FOR
BRIDGEPORT SERIES 1 MILLS
The Rockford Ball Screw retrofit kits are factory set
with the proper preload. Should the ball nut and screw
become disengaged, please contact Rockford Ball Screw
Co. Upon receiving screw, make sure the packing slip
lists the proper screws for your machine.
REMOVING EXISTING SCREWS
1 Run the table all the way (Y-Axis) out toward you.
2 Remove the jam nuts and all three bearing brackets.
(One bracket for Y-Axis, one each end of X-Axis.) The
brackets are not all the same so remember where
each one belongs.
3 Remove the gib adjusting screw and pull out the gib.
4 The table should now be loose; slide the table onto a
flat surface which has the same height as the table.
CAUTION: The table is quite heavy.
5 Remove the support housing cap screws and 5/32”
oil lines attached to support housing. (Be careful not
to kink or bend oil lines excessively.)
6 Unscrew both X & Y acme screws from support
housing and remove support housing.
INSTALLING RETROFIT KIT
1 Insert the X-Axis ball screw in the housing. Install (2)
5/16”-24 cap screws provided. Tighten, finger tight
only. The return tubes on ball nut should face up and
fit within slot opening at top of housing.
2 Place housing (and X-Axis screw) in opening in
saddle. The ball nut flange should face to the left.
The bolt holes for the Y-Axis face back of machine.
3 Insert the (4) 3/8” bolts you removed from the old
support housing into the holes in the supplied
housing. Tighten bolts finger tight only.
4 By hand, rotate the Y-Axis nut towards the
unmachined end of the screw. Stop about 1-1 1/2”
from the end of the screw. DO NOT rotate the end of
the screw into the ball nut.
5 Angle the Y-Axis screw into the saddle opening.
(Fig. #1)
6 Push the ball nut beyond the slot in the bottom of
the supplied housing. Then slide the screw into the
slot and pull the ball screw assembly back towards
yourself to seat ball nut in housing.
7 Slide chip plates forward until a 4” x 4” hole appears
behind the supplied housing.
8 Fasten the Y-Axis flange to the housing, using (3)
5/16”-24 screws furnished. This is done through the
chip plate hole behind the saddle. An extension on
a 1/4” socket hex head or a long length of 1/4” hex
stock will make the screw tightening easier. Make
sure the three screws are tight at this time.
9 Clean the ways and oil grooves on the machine.
Test the Bijur System (if applicable) to see if oil is
flowing through the oil holes and through the 5/32”
tubing that lubricates the screw. If you have proper
lubrication, proceed.
10 Install the 5/32” lubrication tubing into the 5/32”
diameter holes located in the flanges on each ball nut
assembly. Just press the tubing into hole as far as it
will go.
ALIGNMENT & REASSEMBLY
1 Replace the bearing bracket (see “Replacement of
Bearings” below) onto the Y-Axis screw. Place one
of the woodruff keys (remove from original screws)
into the Y-Axis screw. Install the handle assembly.
Replace and tighten the bearing bracket bolts.
2 Rotate the Y-Axis handle counterclockwise to move
the table towards you. Snug (slightly) the four bolts
that attach the housing to the saddle. Rotate the
screw to move the table away from you. Let the
housing find its “center” and tighten the screws a bit
more. Repeat this procedure until the torque to turn
the Y-Axis screw seems to be the same throughout
the travel of the screw. Tighten the screws to secure
the housing to the saddle. You may want to drill
some pin holes to secure the housing to the saddle
(optional).
3 Make sure the X-Axis screw ends are equidistant
from center of housing.
4 Install the other woodruff keys into the ends of the
screw.
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X. RETROFIT FOR BRIDGEPORT SERIES 1 MILLS - CONTINUED
5 Slide table back onto ways and assemble the
table gib.
6 Reassemble the right-hand table bearing bracket
finger tight.
7 Reassemble the left-hand table bearing bracket (see
“Replacement of Bearings” below) finger tight.
8 Assemble the dials and handles on both ends.
Run the table through its complete travel in both
directions to center the ball nut within the support
housing. With the table as far to the left (thrust
bearing end) as possible. (Allowing room between
the ball nut and thrust bearings to tighten the cap
screw.) You will need approximately 7” of extension
with a 1/4” hex end to reach the 5/16”-24 screws that
secure the X-Axis nut to support housing.
9 Tighten the X-Axis screws that secure the flange on
the ball nut to the support housing.
10 Tighten the thrust bearing bracket.
11 Run table to far right end. Tighten right hand end
bracket.
12 Check both X-Axis and Y-Axis for full travel and
check torque for alignment. Realign if necessary.
ASSEMBLY INSTRUCTIONS: RETROFIT FOR BRIDGEPORT SERIES 1 MILLS
PROBLEM CAUSES SOLUTION
X-Axis screw won’t accept
bearing brackets.
#1 - Wrong screw length.
#2 - Misalignment.
#1 - Check packing slip
and overall length of screw.
#2 - Realign.
Backlash and/or
“spring” in handle.
#1 - Original bearings are overly worn.
#2 - Preload setting not tight enough.
#1 - Replace bearings with
angular contact bearings.
See attached sheet.
#2 - Consult factory.
Supplied housing bolt holes
won’t line up with saddle.
Slight differences in saddle assembly. Elongate holes in housing.
Screw(s) hard to turn
towards end of travel.
Screw(s) misaligned. Elongate holes in housing.
Rough feel to screw.
#1 - Lack of lubrication.
#2 - Excessive chips or dirt on screw.
#1 - Check lubrication.*
#2 - Clean off screws.
*Lubrication with light weight oil (SAE 5 or 10) is required periodically. If central lube system (Bijur or equivalent) is
available on machine, install a 5/32 diameter line from oil system to ball nut flange. Lubricate with way oil periodically.
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REPLACEMENT OF BEARINGS
The Y-Axis and left-hand end of X-Axis have factory
thrust bearings. These bearings are adequate for use
with acme screws. But if you require zero backlash
and repeatability that our preloaded ball screws allow,
changing the bearings may be required.
There are different grades of angular contact bearings.
The 7204 series of angular contact bearings are the size
required. Be sure to purchase sets that have ground
faces. The minimum type bearings are as follows (or
equivalent):
• Fafnir 7204 WNSU
• FAG 7204B. TVP. UA
• SKF 7204 BYG
There are more precise bearings (much more expensive),
but for most applications on Series I mills, they are not
necessary.
All of the angular contact bearing sets are going to
require a set of spacers. The inner race spacer should
be .115 - .120 thick, an I.D. of .790/.800 and an O.D. of
1.195/1.205. The outer race spacer should be the same
thickness (.115-.120), I.D. of 1.255/1.265 and O.D. of
1.848/1.838 diameter. The inner race spacer should be
placed on the screw before the bearings. The outer race
spacer should be placed in the bearing bore before
installing the bearings. When tightening the bearing
retaining ring, be sure not to tighten too tight. The
bearing retaining ring is made of aluminum and the
screw heads can break through.
The bearings should be packed with grease prior to
assembling and periodically re-greased.
If you have any further problems with bearing
installation, contact your bearing supplier.
X. RETROFIT FOR BRIDGEPORT SERIES 1 MILLS - CONTINUED
CROSS VIEW OF FINAL ASSEMBLY
C
B
A
FIGURE 9
CROSS VIEW OF FINAL ASSEMBLY
940 Southrock Dr. Rockford, IL 61102
800-475-9532
P 815-961-7700
F 815-961-7703
sales@rockfordballscrew.com
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