Rotary Hammer
38 mm (1 - 1/2”)
MODEL HR3851
003098
I N S T R U C T I O N M A N U A L
WARNING:
For your personal safety, READ and UNDERSTAND before using.
SAVE THESE INSTRUCTIONS FOR FUTURE REFERENCE.
w w w. m a k i t a t o o l s . c o m
to whether the outlet is properly
grounded. If the tools should electrically mal-
function or break down, grounding provides a
low resistance path to carry electricity away
from the user.
13. Do not overreach. Keep proper footing
and balance at all times. Proper footing and
balance enables better control of the tool in
unexpected situations.
14. Use safety equipment. Always wear eye
protection. Dust mask, non-skid safety
shoes, hard hat, or hearing protection must
be used for appropriate conditions. Ordinary
eye or sun glasses are NOT eye protection.
5. Avoid body contact with grounded sur-
faces such as pipes, radiators, ranges and
refrigerators. There is an increased risk of
electric shock if your body is grounded.
6. Do not expose power tools to rain or wet
conditions. Water entering a power tool will
increase the risk of electric shock.
Tool Use and Care
15. Use clamps or other practical way to
secure and support the workpiece to a
stable platform. Holding the work by hand or
against your body is unstable and may lead
to loss of control.
7. Do not abuse the cord. Never use the cord
to carry the tools or pull the plug from an
outlet. Keep cord away from heat, oil,
sharp edges or moving parts. Replace
damaged cords immediately. Damaged
cords increase the risk of electric shock.
16. Do not force tool. Use the correct tool for
your application. The correct tool will do the
job better and safer at the rate for which it is
designed.
8. When operating a power tool outside, use
an outdoor extension cord marked “W-A”
or “W”. These cords are rated for outdoor
use and reduce the risk of electric shock.
17. Do not use tool if switch does not turn it
on or off. Any tool that cannot be controlled
with the switch is dangerous and must be
repaired.
Personal Safety
9. Stay alert, watch what you are doing and
18. Disconnect the plug from the power
source before making any adjustments,
changing accessories, or storing the tool.
Such preventive safety measures reduce the
risk of starting the tool accidentally.
use common sense when operating
a
power tool. Do not use tool while tired or
under the influence of drugs, alcohol, or
medication. A moment of inattention while
operating power tools may result in serious
personal injury.
19. Store idle tools out of reach of children
and other untrained persons. Tools are
dangerous in the hands of untrained users.
10. Dress properly. Do not wear loose cloth-
ing or jewelry. Contain long hair. Keep
your hair, clothing, and gloves away from
moving parts. Loose clothes, jewelry, or long
hair can be caught in moving parts.
20. Maintain tools with care. Keep cutting
tools sharp and clean. Properly maintained
tools with sharp cutting edges are less likely
to bind and are easier to control.
11. Avoid accidental starting. Be sure switch
is off before plugging in. Carrying tools with
your finger on the switch or plugging in tools
that have the switch on invites accidents.
21. Check for misalignment or binding of
moving parts, breakage of parts, and any
other condition that may affect the tools
operation. If damaged, have the tool ser-
viced before using. Many accidents are
caused by poorly maintained tools.
12. Remove adjusting keys or wrenches
before turning the tool on. A wrench or a
key that is left attached to a rotating part of
the tool may result in personal injury.
22. Use only accessories that are recom-
mended by the manufacturer for your
3
model. Accessories that may be suitable for
one tool, may become hazardous when used
on another tool.
tenance performed by unqualified personnel
could result in a risk of injury.
24. When servicing a tool, use only identical
replacement parts. Follow instructions in
the Maintenance section of this manual.
Use of unauthorized parts or failure to follow
Maintenance instructions may create a risk of
electric shock or injury.
SERVICE
23. Tool service must be performed only by
qualified repair personnel. Service or main-
USE PROPER EXTENSION CORD: Use only three-wire extension cords that have three-
prong grounding-type plugs and three-pole receptacles that accept the tool's plug. Make
sure your extension cord is in good condition. Replace or repair damaged or worn cord
immediately. When using an extension cord, be sure to use one heavy enough to carry the
current your product will draw. An undersized cord will cause a drop in line voltage resulting
in loss of power and overheating. Table 1 shows the correct size to use depending on cord
length and nameplate ampere rating. If in doubt, use the next heavier gage. The smaller the
gage number, the heavier the cord.
Table 1: Minimum gage for cord
Volts
120 V
Total length of cord in feet
Ampere Rating
25 ft.
50 ft.
100 ft.
150 ft.
More Than
Not More Than
AWG
0
6
10
12
6
18
18
16
14
16
16
16
12
16
14
14
14
12
12
10
12
16
Not Recommended
GROUNDING INSTRUCTIONS
This tool should be grounded while in use to protect the operator from electric shock. The
tool is equipped with a three-conductor cord and three-prong grounding type plug to fit the
proper grounding type receptacle. The green (or green and yellow) conductor in the cord is
the grounding wire. Never connect the green (or green and yellow) wire to a live terminal.
Your unit is for use on 120 volts and has a plug that looks like Fig. “A”.
4
An adapter Fig. “B” and “C” is available for connecting Fig. “A” type plugs to two-prong
receptacles. The green-colored rigid ear, lug, etc., extending from the adapter must be con-
nected to a permanent ground, such as a properly grounded outlet box.
Adapter
Grounding Means
Cover of Grounded
Grounding
Blade
Outlet Box
Fig. A
Fig. B
Fig. C
SPECIFIC SAFETY RULES
USB010-2
DO NOT let comfort or familiarity with product (gained from
repeated use) replace strict adherence to rotary hammer safety
rules. If you use this tool unsafely or incorrectly, you can suffer
serious personal injury.
1. Hold tools by insulated gripping surfaces
when performing an operation where the
cutting tool may contact hidden wiring or
its own cord. Contact with a “live” wire will
make exposed metal parts of the tool “live”
and shock the operator.
4. Be sure the bit is secured in place before
operation.
5. Under normal operation, the tool is
designed to produce vibration. The
screws can come loose easily, causing a
breakdown or accident. Check tightness
of screws carefully before operation.
2. Wear ear protectors when using the tool
for extended periods. Prolonged exposure
to high intensity noise can cause hearing
loss.
6. In cold weather or when the tool has not
been used for a long time, let the tool
warm up for a while by operating it under
no load. This will loosen up the lubrica-
tion. Without proper warm-up, hammering
operation is difficult.
3. Wear a hard hat (safety helmet), safety
glasses and/or face shield. Ordinary eye
or sun glasses are NOT safety glasses. It
is also highly recommended that you wear
a dust mask and thickly padded gloves.
7. Always be sure you have a firm footing.
Be sure no one is below when using the
tool in high locations.
5
8. Hold the tool firmly with both hands.
9. Keep hands away from moving parts.
12. Do not touch the bit or parts close to the
bit immediately after operation; they may
be extremely hot and could burn your
skin.
10. Do not leave the tool running. Operate the
tool only when hand-held.
13. Some material contains chemicals which
may be toxic. Take caution to prevent dust
inhalation and skin contact. Follow mate-
rial supplier safety data.
11. Do not point the tool at any one in the area
when operating. The bit could fly out and
injure someone seriously.
SAVE THESE INSTRUCTIONS
WARNING:
MISUSE or failure to follow the safety rules stated in this
instruction manual may cause serious personal injury.
6
FUNCTIONAL
DESCRIPTION
CAUTION:
•
Always be sure that the tool is switched off and
unplugged before adjusting or checking function on the
tool.
003111
Switch action
CAUTION:
1
•
Before plugging in the tool, always check to see that the
switch trigger actuates properly and returns to the “OFF”
position when released.
To start the tool, simply pull the switch trigger. Release the
switch trigger to stop.
1. Switch trigger
003127
Selecting the action mode
1
2
3
Rotation with hammering
For drilling in concrete, masonry, etc., rotate the change lever
to the
symbol.
Hammering only
For chipping, scaling or demolition operations, rotate the
change lever to the
symbol.
1. Change lever
2. For hammering only
CAUTION:
3. For rotation with hammering
•
•
Do not rotate the change lever when the tool is running
under load. The tool will be damaged.
To avoid rapid wear on the mode change mechanism, be
sure that the change lever is always positively located in
one of the two action mode positions.
7
ASSEMBLY
CAUTION:
•
Always be sure that the tool is switched off and
unplugged before carrying out any work on the tool.
003146
Side grip (auxiliary handle)
For maximum control and safer operation, always use the
side grip with this tool. The side grip swings around to either
side, allowing easy handling of the tool in any position.
Loosen the side grip by turning it counterclockwise, swing it
to the desired position and then tighten it by turning clock-
wise.
1
2
1. Side grip
2. Grip base
003149
The side grip can also be installed in the position shown in
the figure. Remove the side grip from the grip base by turn-
ing the side grip counterclockwise. Screw the side grip on
either side of the tool, whichever is convenient.
Installing or removing the bit
003153
Press in the tool retainer and turn it until the red dots on the
tool retainer and the tool holder are aligned. Release the tool
retainer.
1
2
1. Red dot (Tool holder)
2. Rde dot (Tool retainer)
003154
Insert the bit into the tool holder as far as it will go. Press in
the tool retainer and turn it a full 180 degrees. Then release it
to secure the bit.
1
3
2
To remove the bit, follow the installation procedure in reverse.
1. Tool retainer
2. Turn 180°
3. Press in
8
003183
Depth gauge
The depth gauge is convenient for drilling holes of uniform
depth. Insert the depth gauge into the hole in the grip base.
Adjust the depth gauge to the desired depth and then tighten
the clamp screw to secure the depth gauge.
1
3
NOTE:
2
•
The depth gauge cannot be used at the position where
the depth gauge strikes against the tool body.
1. Clamp screw
2. Depth gauge
3. Grip base
OPERATION
003199
Hammer drilling operation
Set the change lever to the
symbol.
Position the bit at the desired location for the hole, then pull
the switch trigger. Do not force the tool. Light pressure gives
best results. Keep the tool in position and prevent it from slip-
ping away from the hole.
Do not apply more pressure when the hole becomes clogged
with chips or particles. Instead, run the tool at an idle, then
remove the bit partially from the hole. By repeating this sev-
eral times, the hole will be cleaned out and normal drilling
may be resumed.
CAUTION:
•
There is a tremendous and sudden twisting force
exerted on the tool/bit at the time of hole break-through,
when the hole becomes clogged with chips and
particles, or when striking reinforcing rods embedded in
the concrete. Always use the side grip (auxiliary handle)
and firmly hold the tool by both side grip and switch
handle during operations. Failure to do so may result in
the loss of control of the tool and potentially severe
injury.
002449
Blow-out bulb (optional accessory)
After drilling the hole, use the blow-out bulb to clean the dust
out of the hole.
1
1. Blow-out bulb
9
003205
Chipping/Scaling/Demolition
Set the change lever to the
symbol.
Hold the tool firmly with both hands. Turn the tool on and
apply slight pressure on the tool so that the tool will not
bounce around, uncontrolled. Pressing very hard on the tool
will not increase the efficiency.
Core bit (optional accessory)
When using the center bit
003209
Screw the core bit on the adapter. Install the adapter with the
core bit in the tool in the same manner as a drill bit.
1
2
1. Core bit
2. Adapter
003210
Install the center bit.
1
1. Center bit
003211
Rest the core bit on the concrete and turn the tool on. Once
the core bit has cut a shallow groove into the concrete,
remove the center bit. Then resume drilling.
10
To remove the core bit, follow the procedures 1 or 2.
003213
1. Rotate the change lever to the
position. Then rest
the core bit on the concrete and turn the tool on. The
core bit will come loose from the hammering action.
003215
2. Hold the adapter with the wrench, insert the rod (optional
accessory) into the hole in the core bit and tap with a
hammer to unscrew.
1
1. Rod
003216
When not using the center bit
1
2
Screw the core bit on the adapter. Install the adapter with the
core bit in the tool in the same manner as a drill bit.
1. Core bit
2. Adapter
003211
Rotate the change lever to the
position. Rest the core bit
on the concrete and turn the tool on. Once the core bit has
cut a shallow groove into the concrete, rotate the change
lever to the
position and resume drilling.
NOTE:
•
No problem is caused even if the core bit unscrews
slightly during brief use since the core bit rotates in the
tightening direction.
To remove the core bit, follow the same removal procedures
covered in “When using the center bit”.
MAINTENANCE
CAUTION:
•
Always be sure that the tool is switched off and
unplugged before attempting to perform inspection or
maintenance.
11
001146
Replacing carbon brushes
When the resin insulating tip inside the carbon brush is
exposed to contact the commutator, it will automatically shut
off the motor. When this occurs, both carbon brushes should
be replaced. Keep the carbon brushes clean and free to slip
in the holders. Both carbon brushes should be replaced at
the same time. Use only identical carbon brushes.
2
3
1
1. Commutator
2. Insulating tip
3. Carbon brush
003225
Use a hex wrench to remove the rear cover.
1
2
1. Hex wrench
2. Rear cover
003231
Use a screwdriver to remove the brush holder caps. Take out
the worn carbon brushes, insert the new ones and secure
the brush holder caps.
1
2
1. Screwdriver
2. Brush holder cap
Lubrication
003236
This tool requires no hourly or daily lubrication because it
has a grease-packed lubrication system. It should be relubri-
cated after every 6 months of operation. Send the complete
tool to Makita Authorized or Factory Service Center for this
lubrication service. However, if circumstances require that
you should lubricate it by yourself, proceed as follows.
1
2
Run the tool for several minutes to warm it up. Switch off and
unplug the tool.
1. Lock nut wrench
2. Crank cap
Remove the crank cap using a Makita lock nut wrench 35
(optional accessory). Rest the tool on the table with the bit
end pointing upwards. This will allow the old grease to collect
inside the crank housing.
12
Wipe out the old grease inside and replace with a fresh
grease (60 g; 2 oz). Use only Makita genuine hammer
grease (optional accessory). Filling with more than the spec-
ified amount of grease (approx. 60 g; 2 oz) can cause faulty
hammering action or tool failure. Fill only with the specified
amount of grease.
Reinstall the crank cap and tighten with the lock nut wrench.
CAUTION:
•
Do not tighten the crank cap excessively. It is made of
resin and is subject to breakage.
To maintain product SAFETY and RELIABILITY, repairs, any
other maintenance or adjustment should be performed by
Makita Authorized or Factory Service Centers, always using
Makita replacement parts.
ACCESSORIES
CAUTION:
•
These accessories or attachments are recommended for
use with your Makita tool specified in this manual. The
use of any other accessories or attachments might
present a risk of injury to persons. Only use accessory
or attachment for its stated purpose.
If you need any assistance for more details regarding these
accessories, ask your local Makita service center.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Spline shank Carbide-tipped bits
Bull point
Cold chisel
Scaling chisel
Grooving chisel
Spline shank to A-Taper adapter
Spline shank to SDS adapter
Core bit
Core bit adapter
Hammer grease
Depth gauge
Blow-out bulb
Safety goggles
Lock nut wrench 35
Hex wrench
Plastic carrying case
13
Memo
14
Memo
15
Memo
16
First-Class
Postage
Required
Post Office will
not deliver
without proper
postage.
Makita U.S.A., Inc.
14930 Northam Street
La Mirada, CA 90638-5753
Fold
MAIL THIS PORTION
Your answers to the following questions are appreciated.
1. This product was purchased from:
3. How did you learn about this product:
Home Center
Other (
)
Magazine
Radio
Hardware/Lumber Store
Tool Distributor
From Dealer
Newspaper
Store Display
Catalog
Exhibition
From Friend
Previous Usage
Other (
Industrial Supply
Construction Supply
)
2. Use of the product is intended for:
4. Most favored points are:
Construction Trade
Industrial Maintenance
Home Maintenance
Hobby
Design
Repair Service
Durability
Power
Features
Size
Price
Other (
)
Other (
)
Makita Brand
5. Any comments:
DATE PURCHASED
MONTH
MODEL NO.
DAY
YEAR
SERIAL NO.
STATUS
SEX
Married Single
M
F
INTL.
LAST NAME / COMPANY NAME
STREET ADRESS
CITY
AREA
CODE
STATE
ZIP CODE
PHONE
40-49
Under 19
20-29
30-39
50-60
Over 60
AGE:
BE SURE TO COMPLETE THE CUSTOMER’S PORTION OF THIS FORM AND RETAIN FOR YOUR RECORDS.
Please return this portion by facsimile or mail.
Facsimile No: (714) 522-8133
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FACTORY SERVICE CENTERS
1-800-4-MAKITA
RETAIN THIS PORTION FOR YOUR RECORDS
ALABAMA
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KENTUCKY
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(205) 620-1791
11839 E. 51st Ave.
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(303) 371-2850
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Louisville, KY 40222
(502) 326-3740
5805 Menaul Blvd. NE
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ARIZONA
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Windsor Locks, CT 06096
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LOUSIANA
NEW YORK
TENNESSEE
3707 E. Broadway Rd., Ste. 6
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(602) 437-2850
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(504) 733-4138
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Cheektowaga, NY 14225
(716) 685-9503
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Flushing, NY 11354
(718) 886-0971
ARKANSAS
FLORIDA
MARYLAND
TEXAS
Shackleford Shopping Center
240 South Shackleford Rd.,
Ste. C
620 Douglas Ave. Suite 1302
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(407) 774-6000
7541 - 45 Ritchie Highway
Glen Burnie, MD 21061
(410) 590-0160
12801 Stemmons Fwy Ste. 809
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(972) 243-1150
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(501) 224-5733
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3501-G S. Tryon St.
Charlotte, NC 28217
(704) 527-0611
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(210) 228-0676
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Columbus, OH 43213
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GEORGIA
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102
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53227
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Suites. 22 - 24
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CUSTOMER’S RECORD
Date Purchased
When you need service: Send
complete tool (prepaid) to one
of the Makita Factory Service
Centers listed, or to an Authorized
Makita Service Center. Be sure
to attach a letter to the outside of
the carton detailing the problem
with your tool.
Dealer’s Name & Address
Model No.
Serial No.
19
WARNING
Some dust created by power sanding, sawing, grinding, drilling, and other
construction activities contains chemicals known to the State of California
to cause cancer, birth defects or other reproductive harm. Some examples
of these chemicals are:
• lead from lead-based paints,
• crystalline silica from bricks and cement and other masonry products, and
• arsenic and chromium from chemically-treated lumber.
Your risk from these exposures varies, depending on how often you do this
type of work. To reduce your exposure to these chemicals: work in a well
ventilated area, and work with approved safety equipment, such as those
dust masks that are specially designed to filter out microscopic particles.
MAKITA LIMITED ONE YEAR WARRANTY
Warranty Policy
Every Makita tool is thoroughly inspected and tested before leaving the factory. It is warranted to be free of
defects from workmanship and materials for the period of ONE YEAR from the date of original purchase.
Should any trouble develop during this one-year period, return the COMPLETE tool, freight prepaid, to one of
Makita's Factory or Authorized Service Centers. If inspection shows the trouble is caused by defective
workmanship or material, Makita will repair (or at our option, replace) without charge.
This Warranty does not apply where:
• repairs have been made or attempted by others:
• repairs are required because of normal wear and tear:
• the tool has been abused, misused or improperly maintained:
• alterations have been made to the tool.
IN NO EVENT SHALL MAKITA BE LIABLE FOR ANY INDIRECT, INCIDENTAL OR CONSEQUENTIAL
DAMAGES FROM THE SALE OR USE OF THE PRODUCT. THIS DISCLAIMER APPLIES BOTH DURING
AND AFTER THE TERM OF THIS WARRANTY.
MAKITA DISCLAIMS LIABILITY FOR ANY IMPLIED WARRANTIES, INCLUDING IMPLIED WARRANTIES OF
"MERCHANTABILITY" AND "FITNESS FOR A SPECIFIC PURPOSE," AFTER THE ONE-YEAR TERM OF
THIS WARRANTY.
This Warranty gives you specific legal rights, and you may also have other rights which vary form state to state.
Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above
limitation or exclusion may not apply to you. Some states do not allow limitation on how long an implied
warranty lasts, so the above limitation may not apply to you.
Makita Corporation
3-11-8, Sumiyoshi-cho,
Anjo, Aichi 446-8502 Japan
883481F063
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