Makita HM1242C Manual

Continuous Rating (W)
Voltage (V) Cycle (Hz) Input Output Max. Output(W)
100
115
220
230
240
Models No.
Description
PRODUCT
Current (A)
TECHNICAL INFORMATION
CONCEPTION AND MAIN APPLICATIONS
Specification
Standard equipment
Optional accessories
< Note > The standard equipment for the tool shown may be differ from country to country.
P 1/ 12
HM1242C
Demolition Hammer
112mm(4-3/8")
258mm(10-1/8")
572mm(22-1/2")
HM1242C is the 10 Kg class hammer for BOSCH shank type
hammer bits (3/4" Hex 21/32 Round shank)
This model is taking over the existing HM1202C's benefits
in incredibly low noise, compact body and the strongest
demolishing power in this class.
15
15
120 13
7.3
7.0
6.7
50 / 60
50 / 60
50 / 60
50 / 60
50 / 60
50 / 60
1,450
1,450
1,450
1,450
1,450
1,450
500
500
500
550
550
550
1,600
1,600
1,600
1,800
1,800
1,800
Bit-type
950-1,900 (bpm)
Blows per minute
Net Weight 9.3kg (20.5 lbs)
Cord Length 5m (16.4 ft)
Size of shank
BOSCH shank type
hammer bits
(3/4" Hex 21/32 Round shank)
Grease for bit ........... 1 pc.
Bull point 19-300
Bull point 19-450
Cold chisel 26-300
Cold chisel 26-450
Scaling chisel 50-300
Grooving chisel 22-300
Grooving chisel 26-300
Clay spade 105-400
Rammer 140
Bushing tool 67-300

<1> Removing armature
(1) Take off the rear cover from the motor housing
by loosening 2 pcs.of tapping screw M4x18.
And then take off the carbon brushes after
taking off the brush holder cap.
(2) Take off the handle and controler cover
by loosening 2 pcs.of hex socket hd.bolt M6x40
and 4 pcs.of hex socket hd.bolt M6x30.
(3) Dismount the motor housing by loosening
4 pcs.of hex socket hd.bolt M6x40.
(4) Support the machine with the repairing jig No.1R023,
1R218 and 1R022.
Put a round stick (repairing jig No.1R234 or 1R235)
on the armature
The armature can be removed from the
motor housing by pushing the above round stick
with arbor press.
Screwdriver
Brush Holder Cap
Tapping screw M4x18
Hex socket hd.bolt M6x40
Hex socket hd.bolt M6x30
Controler cover
Hex socket hd.bolt M6x40
Motor housing
Base of arbor press Armature
1R022
1R023
1R218
1R234 or
1R235
Arbor press
P 2/ 12
Repair
Fig.1
Fig.2
Fig.3
Fig.4

(5) Removing ball bearing 6304LLU from crank shaft.
Insert the repairing jig 1R234, 1R240 and 1R241 into the arbor on the crank shaft as per
the following illustration. And then, press with arbor press. So, Ball bearing 6304LLU can be removed.
Arbor press
Crank shaft
Base of arbor press
Ball bearing 6304LLU
1R234 1R240
1R241
1R032 - 1R037
1R034
(Mounting)
Make sure that the gears engage each other, before pressing the armature
with arbor press into crank housing.
<2> Repairing on chuck section
Repairing on chuck section has to be made
with installing controller cover, because it is difficult
to keep the machine standing without it.
(Dismounting)
(1) Pull tool holder cover down in the direction
of the motor housing.
Dismount tool holder cap.
Arbor press
Tool holder cap
Tool holder cover
P 3/ 12
Repair
Fig.5
Fig.6
Fig.7

Repair P 4/ 12
(2) Pulling tool holder cover down
in the direction of the motor housing,
slide the cut of ring spring 29 in the
direction of the cut of tool holder cover.
And expand the cut of ring spring 29 with,
repairing tool No.1R212, lifting it with
driver as illustrated in Fig.8.
(3) Tool holder, roller guide and pin 6 can be
removed as a set, with removing
ring spring 29.
Roller guide can be removed from tool
holder cover, with taking off pin 6.
Fig.9
Fig.8
No.1R212 Cut of tool
holder cover
Ring spring 29
Tool holder cover
Pin 6
Roller guide
Tool holder cover
<3> Repairing of piston and striker
Take off only handle, not remove controller cover.
(Dismounting)
(1) Take off change ring after removing
chuck section.
And then, take off ring spring 46
with pawl for retaining ring .
Dismount housing cover.
Ring spring 46
Housing cover
No.1R212
Pawl for retaining ring
Fig.10
(2) Loosen 4 pcs. of hex socket head bolt M8x30.
Then barrel can be removed together with
tool holder. Hex socket head bolt M8x30
(4 pcs.)
Barrel
Fig.11

Repair P 5/ 12
(3) Hold cylinder liner 44 with hand and
strike crank housing with plastic or
wooden hammer.
Then the cylinder liner 44 can be
removed from the machine.
Cylinder liner 44
Crank housing
Fig.12
(Assembling)
(1) Assemble slide sleeve 49, ring 49 and
compression spring 50 to cylinder liner 44.
And then, put the cylinder liner 44 on piston.
Mount the cylinder liner to the crank housing
by pressing it with hand.
Insert striker into the cylinder liner from
the bit-installing side.
Compression spring 50
Striker
Ring 49
Slider sleeve 49
Cylinder liner 44
Crank housing
Piston
Fig.13
(2) Adjust the convex of tool holder cap
to the concave of tool holder cover.
Make sure that tool holder cap does
not turn after assembling. Tool holder cap
Tool holder cover
Tool holder
Adjust the convex of tool holder cap
to the concave of tool holder cover.
Fig.14
<4> Repairing of tool holder
Take off only handle, not remove controller cover.
(Dismounting)
Take off flat washer 37 after removing
ring spring 34.
Remove tool holder from barrel by pressing .
Tool holder
Ring spring 34
Barrel
Flat washer 37

Repair P 6/ 12
(Assembling)
(1) Assemble tool holder to barrel after
inserting impact bolt as illustrated in Fig.16.
( Note )
Make sure, that urethane ring 43 and O ring 38
are assembled to tool holder in advance.
( Note )
The mark, " UP " has to be faced to the bit
installing side as illustrated in Fig.17A.
Barrel O ring 38
Urethane ring 43
Impact bolt
Tool holder
Barrel
Tool holder
Ring spring 34
Flat washer 37
Fig.16
Fig.17
(2) Assemble flat washer 37 to tool holder
after assembling tool holder to barrel.
And then, fix flat washer 37 with
ring spring 34.
Bit installing side UP
UP
Fig.17A
< 5> Assembling fluoride ring
(Assembling)
(1) Fluoride ring 28, just after assembled, can not be fit
precisely along the groove on the impact bolt.
The edge come out from the groove.
(2) Insert the impact bolt on which the fluoride
ring 28 is attached, into repairing jig No.1R-214.
At this time the impact bolt has to be inserted
from the hole for [HR5001C]
And then, keep the impact bolt in the repairing jig
approx. 10 sec for correction of fluoride ring 28.
(3) Pay attention, not to damage fluoride ring 28, when
the impact bolt is inserted into tool holder.
Fluoride ring 28 of which edge has come out
from the groove.
O ring 23 O ring 23
Fluoride ring 28 corrected
with repairing jig No.1R-214
HR4000C
HR5001C
Repairing jig No.1R-214
(Taper sleeve)
Hole for
[HR5001C]
Fig.18

Repair P 7/ 12
< 6> Mounting of barrel
Take off only handle, not remove controller cover.
(1) Set the of the guide ring on the of flat washer 49.
Mount the above guide ring and flat washer 49 on the 3 prongs
of slide sleeve 49.
(2) Set collared ring 24 ,rubber ring 25 and impact bolt guide
on the 3 prongs of slide sleeve 49.
(3) Set barrel (with tool holder) on the cylinder liner 44 gently paying attention
to keep collared ring 24, rubber ring 25 and impact bolt guide on the slide sleeve's edge.
Assemble compression spring 50 to crank housing by pressing it.
< Remarks>
Pay attention to the position of flat part on barrel as per the following illustration.
Tool holder
Barrel
Impact bold guide
Rubber ring 25 Guide ring
Flat washer 49
Slide sleeve 49
Compression spring 50
Crank housing
Cylinder liner 44
Flat part on barrel
has to face in the direction
of top and bottom.
Collared ring 24
< 7> Mounting of controller cover
Set switch trigger in of switch lever.
ON
I
Fig.19
Fig.20

Repair P 8/ 12
< 8> Grease
Change of grease
Change grease to fresh one when carbon brush is changed.
(1) Idle the machine for several minutes in order to warm up.
(2) Take off the handle and controller cover
by loosening 2 pcs.of hex socket hd.bolt M6x40
and 4 pcs.of hex socket hd.bolt M6x30.
And then, crank housing appears.
Hex socket hd.bolt M6x40
Hex socket hd.bolt M6x30
Handle
Crank Housing
Crank Cap
Controller cover
< Remarks >
The fresh grease to be applied has to
be limited to 30 g.
Over application can be cause of trouble.
(3) Take off crank cap.
(4) Gather the grease softened by warming up, into
the crank housing by facing the tool holder cap side
to upward.
(5) Wipe up the grease
in the crank housing
with cloth. And then, apply fresh MAKITA grease
No.00 by 30g.
Fig.21
Fig.22

Repair P 9/ 12
* The parts to be greased with MAKITA grease No.OO.
Put grease on the following parts in order to protect parts and machine from unusual abrasion
and overheating.
O ring23
Fluoride ring 28 Impact bolt Striker O ring34
O ring34 Piston Holes of Piston
Cylinder liner 44: Surface marked with
Slide sleeve 49 Ring 49
Cylinder
liner 44
Impact bolt guide Collard sleeve
Rubber ring 25
Barrel : Inner part marked with and .
Gear part of Crank shaft
Tool holder and its holes
for roller 23 and steel ball 5.6.
* The parts to be greased with MAKITA grease No.2.
Put grease on the following parts in order to protect parts and machine from unusual abrasion
and overheating.

Repair P 10/ 12
< 9 > Maintenance
It is recommended to change carbon brush every 140 hours operation. When changing carbon brush,
we recommend you to change the following parts together.
* Grease in crank housing.
Apply fresh grease approx. by 30g. ( See P 10 / 14. )
25
26
29
28
30 Urethane ring 43
32
36
27
56
55
53
49
O ring 34
54
Roller 12 O ring 23
Fluoride ring 28
* Urethane ring 43 and roller 12 to be assembled to (32) tool holder
* Fluoride ring 28 and O ring 23 to be assembled to (36) impact bolt
* Rubber ring 25 to be assembled to cylinder liner 44 unit ( 42: cylinder liner 44 and 43:slide sleeve)
* O ring 34 to be assembled to (49) striker
37
Rubber ring 25
39 40
41
42
43
* O ring 34 to be assembled to (54) piston
* O ring 36 to be assembled to (54) piston
O ring 34
O ring 36
Fig.23
Fig.24
Fig.25