Makita Maktec MT921 Manual

Model No.
Description
PRODUCT
CONCEPT AND MAIN APPLICATIONS
P 1/ 5
Specification
Standard equipment
Optional accessories
Note: The standard equipment for the tool shown above may vary by country.
MT921
Finishing Sander
H
W
Dimensions: mm (")
Width (W)
Height (H)
Length (L) 214 (8-3/8)
92 (3-5/8)
147 (5-3/4)
Continuous Rating (W)
Voltage (V) Cycle (Hz) Input Output
45
Max. Output (W)
110
220
240
1.7
0.9
0.8
50/60
50/60
50/60
180
180
180
60
60
45120 1.6 50/60 --- 60
45230 0.9 50/60 180 60
60
Current (A)
45
45
Pad size: mm (") 93 x 185 (3-5/8 x 7-1/4)
Double insulation
Net weight: kg (lbs)
Power supply cord: m (ft)
Abrasive paper size: mm (") 93 x 228 (3-5/8 x 9)
Yes
Yes
2.0 (6.6)
1.3 (2.9)
Orbits per minute: min.-1= opm 12,000
Strokes per minute: min.-1= spm 24,000
Abrasive paper 93-120 ....................... 1 pc
Abrasive paper 93-60
Abrasive paper 93-80
Abrasive paper 93-100
Abrasive paper 93-120
Abrasive paper 93-150
L
TECHNICAL INFORMATION
Model MT921 has been developed on the design concept;
"easy-to-control" is the key factor to a finishing sander with
strong marketability.
The main benefits are:
Ergonomic grip contoured for easy handling
both in single- and double-handed operation
Industrial performance and durability at less expense
Paper fastening
system
Hook & loop
Clamp
No

P 2/ 5
CAUTION: Unplug the machine for safety before repair/ maintenance in accordance with
the instruction manual!
Repair
[2] Disassembly/ Assembly
[2]-1. Armature
[1] NECESSARY REPAIRING TOOLS
DescriptionCode No.
DISASSEMBLING
1) Remove M4x14 Pan head screw (4pcs.) and Top cover. (Fig. 1)
2) Remove Brush holders together with Carbon brushes.
3) M4x10 Pan head screw (4pcs.) and Pad complete. (Fig. 2)
4) Remove Cap 33 in the center of Base. (Fig. 3)
5) Insert slotted screwdriver between Base and Motor housing, and while
holding Fan 68 as illustrated in Fig. 4, separate Base section from
the machine by removing M4x10 countersunk head screw and Flat
washer 6 that secure Fan 68. (Fig. 5)
6) Remove Fan 68 from Armature. (Fig. 6)
7) Remove 4x18 Tapping screw (4pcs.) for securing Bearing box to
Motor housing. (Fig. 7)
8) Remove Armature together with Bearing box from Motor housing by
striking Motor housing with plastic hammer as illustrated in Fig. 8.
1R027 Bearing setting pipe 18-10.2 Removing Armature
Removing Ball bearing
1R269 Bearing extractor
Use for
Fig. 1
Fig. 4
Fig. 2
Fig. 5
Fig. 8
Fig. 6 Fig. 7
Fig. 3
M4x14 Pan head
screw (4pcs.)
Top cover
M4x10 Pan
head screw (4pcs.)
Pad complete
Cap 33 slotted screwdriver
4x18 Tapping screw (4pcs.)
Bearing
box
Fan 68
slotted
screwdriver
Fan 68
Fan 68
M4x10 countersunk
head screw Base section
plastic hammer
Armature
Bearing box
Flat washer 6
Motor housing

P 3/ 5
Repair
[2] Disassembly/ Assembly
[2]-1. Armature (cont.)
DISASSEMBLING
DISASSEMBLING
9) Remove Armature from Bearing box by striking the armature shaft end.
When it is difficult to remove Armature in the above manner, put
Bearing box on U-shape base of arbor press, then press down
Ball bearing 6200LLB of Armature using 1R027 and arbor press.
(Fig. 9)
10) Remove Ball bearing 606ZZ from the commutator-end of Armature shaft
using 1R269 and waterpump pliers. (Fig. 10)
Note: Be sure to firmly hold the jaws of 1R269 with waterpump pliers
because the space between Insulation washer and Ball bearing
606ZZ is so tight that Ball bearing 606ZZ cannot be securely
held with the jaws of 1R269.
11) Remove Ball bearing 6200LLB from the drive-end of Armature shaft
using 1R269. (Fig. 11)
Note: Before attaching 1R269 to Ball bearing 6200LLB, be sure to
fasten M4x10 +Countersunk head screw to the drivee-end of
Armature shaft in order not to damage to the threads inside
Armature shaft.
Fig. 9
Fig. 10 Fig. 11
M4x10 +Countersunk
head screw
1R027
Ball bearing
6200LLB of
Armature
1R269 waterpump pliers
Ball bearing 606ZZ
Ball bearing
6200LLB
Flat washer 10
Take the disassembling step in reverse.
Note: Be sure to set Flat washer 10 in place before pressfitting Ball bearing 6200LLB to Armature shaft. (Fig. 11)
Insulation washer
Bearing box
U shape base
of arbor press

P 4/ 5
Circuit diagram
Fig. D-1
Power supply cord
Brown color is used
for some countries.
Switch
Brush holder A
Terminal block
(if used)
Viewed from Top cover
Field
Noise suppressor
(if used)
Blue color is used
for some countries.
Power supply cord
Brush holder B
Brush
holder B
Brush
holder A
Color index of lead wires' sheath
Black
White
Orange
Purple

P 5/ 5
Wiring diagram
Fig. D-2
Power supply cord
small notch
Lead wires
Set Terminal block (if used)
into place between four ribs.
Switch
Brush holder BBrush holder A
Insulated terminal
Insulated terminal
Area BArea A
Fix Field lead wires with Lead
wire holders to prevent slacks
near Armature.
Fix Field lead wires
with Lead wire holders
to prevent slacks near
Armature.
Connect Insulated terminals A and B
with Brush holders A and B.
And set each Brush holders carefully in
place so as not to put on Areas A and B
illustrated left.
(Bending the insulated terminals is
allowed.)
Field lead wireField lead wire
Noise suppressor
(if used)
Set Noise suppressor in place so that
the lead wires face the inserted direction
and the lead wires pass through the small notch.