SERVICE INSTRUCTIONS FOR
3M™ 12,000 RPM 5 in. (127 mm)
and 6 in. (150 mm)
RANDOM ORBITAL SANDERS
3M™ Overhaul Service Kit
The part number 20347, 3M™ Overhaul Service Kit, contains all the replacement parts that naturally
wear over time and a straightforward manual to make servicing a 3M™ sander simple. Overhauling the
Random Orbital Sander can be made even easier with the use of the above Service Tools. The Service
Tools also reduce the chance of improper assembly.
Part Number
3MA0040
3MA0021
3MB0005
3MA0010
3MA0041
3MA0042
3MA0019
3MA0938
3MA0039
3MA0062
3MA0068
3MA0007
3MA0009
3MA0014
3MA0043
3MA0008
3MA0166
3MA0016
3MA1417
Description
Qty
1
1
1
5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
EXTERNAL RETAINING RING
BEARING - 2 SHIELDS
ROTOR
VANE
WOODRUFF KEY
O-RING
BEARING - 2 SHIELDS
DOUBLE ROW ANGULAR CONTACT BEARING - 1 SEAL
INTERNAL RETAINING RING
INTERNAL MUFFLER
MUFFLER INSERT
VALVE
VALVE SEAT
VALVE SPRING
O-RING
VALVE STEM ASSEMBLY
MUFFLER HOUSING
SPACER
INSTRUCTIONS FOR 5 in. AND 6 in. ROS OVERHAUL SERVICE KIT
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B) Remove the Ø 1 in. (28 mm) Hose SGV Swivel Exhaust
Assembly from the Housing and SGV Skirt Adapter or
SGV Shroud Adapter.
4. For NV and CV machines follow the steps outlined in
Section I below. For SGV machines follow the steps in
Section III.
C) Pull the SGV Retainer out of the bore of the Swivel
Exhaust Assembly and remove the two O-rings.
D) Remove the Vacuum Shroud or Vacuum Skirt from the
Housing. Move onto step 2.
I. This section is for CV and NV
A) Place a clean felt Muffler all-the-way into the chamber of
the Muffler Housing. Press the Bronze Muffler onto the
Muffler Housing.
2. Place the Speed Control to the midway position and
remove the Retaining Ring. NOTE: If the machine is a
vacuum model, the vacuum exhaust must be removed
(see Section 1 above for removal) before the Retaining
Ring can be removed with lock ring pliers. The Speed
Control will now pull straight out. Remove the O-ring.
3. Unscrew the Inlet Bushing Assembly from the Housing.
Remove the Valve Spring, Valve, Valve Seat, Valve
Stem and O-Ring.
B) Screw the Muffler Housing assembly into the Housing
until hand tight. Use a 21 mm socket/torque wrench
combination to torque the Muffler Housing. Torque to 20
in/lbs (2.25 Nm). For NV machines move onto C. For CV
machines move onto Section II.
C) Install the Non-Vacuum Shroud onto the Housing by
working the shroud over and around the bottom of the
housing flanges. Make sure the line up slots (on the
Housing) and tabs (on the Shroud) are engaged. Move
onto the ”Spindle, bearing shield and Shaft Balancer
Assembly” Section.
4. Press out the Spring Pin from the Housing and remove
the Throttle Lever.
ASSEMBLY INSTRUCTIONS
II. This section continued from Section I for CV Ex-
haust machines:
NOTE: All assembly must be done with clean dry parts and
all bearings are to be pressed in place by the correct tools
and procedures as outlined by the bearing manufacturers.
Housing Assembly:
1. Install Throttle Lever into Housing with the Spring Pin.
2. Lightly grease the O-ring and place it on the Speed
Control. Install Valve Stem, O-ring (cleaned and lightly
greased) and insert the Speed control into the Hous-
ing in the midway position. Install the Retaining Ring.
CAUTION: Make sure the Retaining Ring is completely
snapped into groove in the Housing.
3. Install the Valve Seat, the Valve and the Valve Spring.
Coat the threads of the Bushing Assembly with 1 or 2
drops of 3M Rite-Loc TL22 or equivalent non-permanent
pipe thread sealant. Screw the assembly into the Hous-
ing. Torque to 60 in/lbs (6.77 Nm.)
A) For 5 and 6 in. (125 and 150 mm) machines:
(1) Install the 5 or 6 in. (125 or 150 mm. ) Shroud or 6 in.
(150 mm) Clean Sanding Shroud onto the Housing by
working the shroud over and around the bottom of the
housing flanges. Slide the inlet end of the Ø 1 in. (28
mm) CV Swivel Exhaust Assembly or the Ø 3/4 in. (19
mm) CV Swivel Exhaust Assembly into the exhaust port
of the Shroud or Clean Sanding Shroud until it hits the
stop on the Swivel Exhaust Assembly.
NOTE: For installation of Shrouds and Skirts make sure the
line up slots (on the Housing) and tabs (on the Shroud or
Skirt) are engaged. Make sure that the key on the Swivel
Exhaust Assembly bracket is aligned and engaged with the
keyway on the Housing.
B) Place the Washer over the Screw. Thread the screw
T-1B
Bearing
Press Tool Top
Shim
Washer
Press Tool Base
Spindle
T-1A
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into the mounting hole of the Swivel Exhaust Assembly
and Housing until the end of the screw is flush with the
inside surface of the Housing. Place the Nut into the
cavity of the Housing and thread the Screw into the Nut
until tight. Move onto the “Spindle, bearing shield and
Shaft Balancer Assembly” Section.
plate onto the Bearing using the larger end of the T-13
Bearing Press Sleeve until the Front Bearing is seated
in the bearing pocket of the Endplate. CAUTION: Only
press just enough to seat the bearing into the pocket.
Over-pressing can damage the bearing.
3. Place the Key into the groove on the Shaft Balancer.
Place the Rotor on the Shaft Balancer, making sure that
it is a tight slip fit.
4. Oil the five Vanes with a quality pneumatic tool oil and
place them in the slots of the Rotor. Place the Cylinder
Assembly over the Rotor with the short end of the
Spring Pin engaging the blind hole in the Front End-
plate. NOTE: The Spring Pin must project .060 in. (1.5
mm) above the flanged side of the Cylinder.
III. This section for SGV Exhaust machines:
A) Install the Shroud or SGV Vacuum Skirt onto the Hous-
ing by working the shroud or skirt over and around the
bottom of the housing flanges. Make sure the line up
slots (on the Housing) and tabs (on the Shroud or Skirt)
are engaged.
B) Attach the SGV Skirt Adapter or SGV Shroud Adapter to
the exhaust port of the Shroud or SGV Skirt.
C) Clean and lightly grease the two O-rings and place them
in the two grooves in the SGV Retainer.
5. Press fit the rear Bearing (2 shields) into the Rear
Endplate with the T-1B Bearing Press Tool. Make sure
the T-1B Press Tool is centered on the O.D. of the outer
race. Lightly press fit the Rear Endplate and Bearing
Assembly over the Shaft Balancer using the small end
of the T-13 Bearing Press Sleeve. The sleeve should
press only the inner race of the bearing. IMPORTANT:
The Rear Endplate and Bearing Assembly is pressed
correctly when the Cylinder is squeezed just enough
between the Endplates to stop it from moving freely
under its own weight when the shaft is held horizontal,
but be able to slide between the Endplates with a very
light force. If the assembly is pressed to tightly the
motor will not run freely. If the pressed assembly is to
loose, the motor will not turn freely after assembly in the
Housing. Secure the assembly by placing the Retaining
Ring in the groove of the Shaft Balancer. CAUTION: The
Retaining Ring must be placed so that the middle and
two ends of the hoop touch the Bearing first. Both raised
center portions must be securely “snapped” into the
groove in the Shaft Balancer by pushing on the curved
portions with a small screwdriver.
D) Put the SGV Retainer into the mounting hole of the Ø 1
in. (28 mm) Hose SGV Swivel Exhaust Assembly.
E) Push the Ø 1 in. (28 mm) Hose SGV Swivel Exhaust
Assembly into the exhaust port of the SGV Skirt Adapter
or SGV Shroud Adapter. Screw the SGV Retainer into
the threaded exhaust port on the Housing with an 8 mm
Hex Wrench. Torque to 45 in/lbs (5.08 Nm. ).
Spindle, Bearing Shield and Shaft Balancer Assembly:
1. Place the Washer and Shim on the Spindle shaft with
the curve of the Washer facing up so that the outside
diameter of the washer will contact the outer diameter of
the Bearing. Place the Bearing on the Spindle with the
seal side toward the Washer. Press onto Spindle using
the T-1B Spindle Bearing Press Tool (see figure) until
seated at bottom.
2. Insert Shim with tangs into the bottom of Spindle Bore
of the Shaft Balancer. (Do not use this shim if Shaft
Balancer text shows a + symbol.)
3. When the Spindle Assembly is done correctly, the Bearing
will rotate freely but not loosely.
4. Take the new Filter and center it on the small bore that
the original Filter was in before removal. With a small
diameter screwdriver or flat-ended rod, press the Filter
into the bore until it is flat in the bottom of the bore.
Place the Valve into the bore so it is oriented correctly,
then press the Retainer into the bore until it is flush with
the bottom of the Bearing bore.
5. Apply a pin head size drop of 3M Rite-Loc TL71 or
equivalent to the outside diameter of each of the bear-
ings on the spindle assembly. Spread the drop of bear-
ing locker around the bearing until distributed evenly.
CAUTION: Only a very small amount of bearing locker
is needed to prevent rotation of the bearing OD. Any ex-
cess will make future removal difficult. Place the Spindle
Assembly into the bore of the Shaft Balancer and secure
with the Retaining Ring. CAUTION: Make sure that the
Retaining Ring is completely snapped into the groove in
the Balancer Shaft. Allow the adhesive to cure.
6. Lightly grease the O-Ring and place in the air inlet of the
Cylinder Assembly.
7. Lightly grease or oil the inside diameter of the Housing,
line up the Spring Pin with the marking on the Housing
and slide the Motor Assembly into the Housing. Make
sure the Spring Pin engages the pocket in Housing.
8. Carefully screw the Lock Ring into the Housing with the
T-6 Motor Lock Ring Wrench/Spindle Puller Tool. Torque
to 60 in/lbs (6.77 Nm.) NOTE: A simple technique
to assure first thread engagement is to turn the lock
ring counter clockwise with the T-6 Motor Lock Ring
Wrench/Spindle Puller while applying light pressure. You
will hear and feel a click when the lead thread of the lock
ring drops into the lead thread of the housing.
9. Spin on a new Pad and hand tighten it using a 24 mm
Pad Wrench.
Testing:
Place 3 drops of quality pneumatic air tool oil directly into
the motor inlet and connect it to a 90 psig (6.2 bar) air
supply. A 12,000 RPM tool should run between 11,500 to
12,000 RPM when the air pressure is 90 psig (6.2 bar) at
the inlet of the tool while the tool is running at free speed.
This free speed will be about 500 RPM to 1,000 RPM less
when a Vacuum or Hook Face Pad is used because of wind
resistance. This will not affect performance when sanding.
Motor Assembly:
1. Use the larger end of the T-13 Bearing Press Sleeve to
press the front Bearing (with 2 Shields) onto the shaft of
the Shaft Balancer.
2. Slide the Front Endplate with the bearing pocket facing
down onto the Motor Shaft. Gently press the Front End-
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Troubleshooting Guide
Symptom
Possible Cause
Solution
Check air line pressure at the Inlet of
the Sander while the tool is running at
free speed. It must be 90 psig (6.2 Bar).
Insufficient Air Pressure
See the “Housing Disassembly” section
for Muffler removal. The Muffler can
be back flushed with a clean, suitable
cleaning solution until all contaminates
and obstructions have been removed. If
the Muffler can not be properly cleaned
then replace it. Replace Muffler Insert
(See the
Clogged Muffler(s)
“Housing Assembly” Section).
Clean the Inlet Screen with a clean,
suitable cleaning solution. If Screen
does not come clean replace it.
Plugged Inlet Screen
Install a complete set of new Vanes
(all vanes must be replaced for proper
operation). Coat all vanes with quality
pneumatic tool oil. See “Motor Disas-
sembly” and
Low Power and/or Low Free Speed
One or more Worn or Broken Vanes
“Motor Assembly”.
Check for proper Motor alignment and
Lock Ring engagement. Check for
damaged O-Ring in Lock Ring groove.
Remove Motor Assembly and Re-Install
the Motor Assembly. See “Motor Disas-
sembly” and “Motor Assembly”.
Internal air leakage in the Motor Housing
indicated by higher than normal air con-
sumption and lower than normal speed.
Overhaul Motor. Contact authorized
Service Center.
Motor Parts Worn
Replace the worn or broken Bearings.
See “Shaft Balancer and Spindle Disas-
sembly” and “Spindle Bearings, Bearing
Shield and Shaft Balancer Assembly”.
Worn or broken Spindle Bearings
Disassemble, inspect and replace worn
Air leakage through the Speed
Control and/or Valve Stem.
Dirty, broken or bent Valve Spring, Valve or damaged parts. See Steps 2 and 3
or Valve Seat.
in “Housing Disassembly” and Steps 2
and 3 in “Housing Assembly”.
Only use Pad Sizes and Weights
designed for the machine.
Incorrect Pad
Only use abrasive and/or interface
designed for the machine. Do not at-
Addition of interface pad or other material tach anything to the Sanders Pad face
that was not specifically designed to be
used with the Pad and Sander.
Disassemble the Sander and clean in
Improper lubrication or buildup of foreign
a suitable cleaning solution. Assemble
debris.
Vibration/Rough Operation
the Sander.
Replace the worn or broken Bearings.
Worn or broken Rear or Front Motor
See “Motor Disassembly” and “Motor
Bearing(s)
Assembly”.
For SGV machines add extra washer(s)
For vacuum machines it is possible to
to the pad spindle to increase the gap
have too much vacuum while sanding on between the pad and shroud. For CV
a flat surface causing the pad to stick to
machines reduce vacuum through
the vacuum system and/or add extra
washer(s) to the pad.
the sanding surface.
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