OPERATOR’S MANUAL
1/2 in. HAMMER DRILL
VARIABLE SPEED
DOUBLE INSULATED
D551H
Your hammer drill has been engineered and manufactured to Ryobi’s high standard for dependability, ease of operation,
and operator safety. When properly cared for, it will give you years of rugged, trouble-free performance.
WARNING: To reduce the risk of injury, the user must read and understand the operator’s manual before using
this product.
Thank you for buying a Ryobi product.
SAVE THIS MANUAL FOR FUTURE REFERENCE
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GENERAL SAFETY RULES
n
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.
WARNING:
Read and understand all instructions. Failure to follow
all instructions listed below, may result in electric shock,
fire and/or serious personal injury.
nRemove 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.
nDo not overreach. Keep proper footing and balance
at all times. Proper footing and balance enables better
control of the tool in unexpected situations.
nUse safety equipment. Always wear eye protection.
Dust mask, nonskid safety shoes, hard hat, or hearing
protection must be used for appropriate conditions.
nDo not wear loose clothing or jewelry. Contain long
hair. Loose clothes, jewelry, or long hair can be drawn
into air vents.
SAVE THESE INSTRUCTIONS
WORK AREA
nKeep your work area clean and well lit. Cluttered
benches and dark areas invite accidents.
nDo not operate power tools in explosive atmospheres,
such as in the presence of flammable liquids, gases,
or dust. Power tools create sparks which may ignite the
dust or fumes.
nKeep bystanders, children, and visitors away while
operating a power tool. Distractions can cause you to
lose control.
nDo not use on a ladder or unstable support. Stable
footing on a solid surface enables better control of the
tool in unexpected situations.
ELECTRICAL SAFETY
TOOL USE AND CARE
nDouble insulated tools are equipped with a polarized
plug (one blade is wider than the other). This plug will
fit in a polarized outlet only one way. If the plug does
not fit fully in the outlet, reverse the plug. If it still
does not fit, contact a qualified electrician to install a
polarized outlet. Do not change the plug in any way.
nUse 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.
nDo not force tool. Use the correct tool for your appli-
cation. The correct tool will do the job better and safer
at the rate for which it is designed.
nDo 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.
nDisconnect the plug from power source before making
any adjustments, changing accessories, or storing the
tool. Such preventive safety measures reduce the risk of
starting the tool accidentally.
nStore idle tools out of the reach of children and other
untrained persons. Tools are dangerous in the hands of
untrained users.
nMaintain 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.
Double insulation
eliminates the need for the three-
wire grounded power cord and grounded power supply
system.
nAvoid body contact with grounded surfaces such as
pipes, radiators, ranges, and refrigerators. There is an
increased risk of electric shock if your body is grounded.
nDon’t expose power tools to rain or wet conditions.
Water entering a power tool will increase the risk of elec-
tric shock.
nDo 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.
n
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.
nCheck for misalignment or binding of moving parts,
breakage of parts, and any other condition that may
affect the tool’s operation. If damaged, have the tool
serviced before using. Many accidents are caused by
poorly maintained tools.
nUse only accessories that are recommended by the
manufacturer for your model. Accessories that may be
suitable for one tool, may become hazardous when used
on another tool.
n Keep the tool and its handle dry, clean and free from
oil and grease. Always use a clean cloth when clean-
ing. Never use brake fluids, gasoline, petroleum-based
products, or any strong solvents to clean your tool.
Following this rule will reduce the risk of loss of control
and deterioration of the enclosure plastic.
PERSONAL SAFETY
nStay alert, watch what you are doing and 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.
nDress properly. Do not wear loose clothing 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.
3
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GENERAL SAFETY RULES
nWhen servicing a tool, use only identical replacement
SERVICE
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
shock or injury.
nTool service must be performed only by qualified
repair personnel. Service or maintenance performed by
unqualified personnel may result in a risk of injury.
SPECIFIC SAFETY RULES
nHold tool 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 cutting
tool “live” and shock the operator.
be carefully checked to determine that it will operate
properly and perform its intended function. Check for
alignment of moving parts, binding of moving parts,
breakage of parts, mounting, and any other conditions
that may affect its operation. A guard or other part that
is damaged should be properly repaired or replaced
by an authorized service center. Following this rule will
reduce the risk of shock, fire, or serious injury.
nKnow your power tool. Read operator’s manual care-
fully. Learn its applications and limitations, as well
as the specific potential hazards related to this tool.
Following this rule will reduce the risk of electric shock, nMake sure your extension cord is in good condition.
fire, or serious injury.
When using an extension cord, be sure to use one
heavy enough to carry the current your product will
draw. A wire gauge size (A.W.G.) of at least 14 is
recommended for an extension cord 50 feet or less
in length. A cord exceeding 100 feet is not recom-
mended. If in doubt, use the next heavier gauge. The
smaller the gauge number, the heavier the cord. An
undersized cord will cause a drop in line voltage resulting
in loss of power and overheating.
nAlways wear safety glasses. Everyday eyeglasses
have only impact-resistant lenses; they are NOT
safety glasses. Following this rule will reduce the risk
of serious personal injury.
nProtect your lungs. Wear a face or dust mask if the
operation is dusty. Following this rule will reduce the
risk of serious personal injury.
nProtect your hearing. Wear hearing protection during
extended periods of operation. Following this rule will
reduce the risk of serious personal injury.
nInspect for and remove all nails from lumber before
using this tool. Following this rule will reduce the risk of
serious personal injury.
nInspect tool cords periodically and, if damaged, have
repaired at your nearest Authorized Service Center.
Constantly stay aware of cord location. Following this
rule will reduce the risk of electric shock or fire.
nSave these instructions. Refer to them frequently and
use them to instruct others who may use this tool. If you
loan someone this tool, loan them these instructions
also.
nCheck damaged parts. Before further use of the
tool, a guard or other part that is damaged should
WARNING:
Some dust created by power sanding, sawing, grinding, drilling, and other construction activities contains chemicals
known 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.
4
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SYMBOLS
Some of the following symbols may be used on this tool. Please study them and learn their meaning. Proper interpreta-
tion of these symbols will allow you to operate the tool better and safer.
SYMBOL
NAME
DESIGNATION/EXPLANATION
V
Volts
Voltage
Current
A
Hz
W
Amperes
Hertz
Frequency (cycles per second)
Watt
Power
min
Minutes
Time
Alternating Current
Type of current
Direct Current
Type or a characteristic of current
Rotational speed, at no load
n
No Load Speed
o
Class II Construction
Per Minute
Double-insulated construction
Revolutions, strokes, surface speed, orbits etc., per minute
.../min
Do not expose to rain or use in damp locations.
Wet Conditions Alert
To reduce the risk of injury, user must read and understand
operator’s manual before using this product.
Read The Operator’s Manual
Always wear safety goggles or safety glasses with side shields,
or a full face shield when operating this product.
Eye Protection
Safety Alert
Precautions that involve your safety.
Failure to keep your hands away from the blade will result in
serious personal injury.
No Hands Symbol
Failure to keep your hands away from the blade will result in
serious personal injury.
No Hands Symbol
No Hands Symbol
Failure to keep your hands away from the blade will result in
serious personal injury.
Failure to keep your hands away from the blade will result in
serious personal injury.
No Hands Symbol
Hot Surface
To reduce the risk of injury or damage, avoid contact with
any hot surface.
5
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SYMBOLS
The following signal words and meanings are intended to explain the levels of risk associated with this product.
SYMBOL
SIGNAL
MEANING
DANGER:
Indicates an imminently hazardous situation, which, if not avoided, will
result in death or serious injury.
WARNING:
Indicates a potentially hazardous situation, which, if not avoided, could
result in death or serious injury.
CAUTION:
CAUTION:
Indicates a potentially hazardous situation, which, if not avoided, may
result in minor or moderate injury.
(Without Safety Alert Symbol) Indicates a situation that may result in
property damage.
SERVICE
WARNING:
Servicing requires extreme care and knowledge and should
be performed only by a qualified service technician. For
service we suggest you return the product to your nearest
AUTHORIZED SERVICE CENTER for repair. When servic-
ing, use only identical replacement parts.
To avoid serious personal injury, do not attempt to use
this product until you read thoroughly and understand
completely the operator’s manual. Save this operator’s
manual and review frequently for continuing safe opera-
tion and instructing others who may use this product.
WARNING:
The operation of any power tool can result in foreign objects being thrown into your eyes, which can
result in severe eye damage. Before beginning power tool operation, always wear safety goggles or
safety glasses with side shields, or a full face shield when needed. We recommend Wide Vision Safety
Mask for use over eyeglasses or standard safety glasses with side shields. Always use eye protection
which is marked to comply with ANSI Z87.1.
SAVE THESE INSTRUCTIONS
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ELECTRICAL
DOUBLE INSULATION
EXTENSION CORDS
Double insulation is a concept in safety in electric power
tools, which eliminates the need for the usual three-
wire grounded power cord. All exposed metal parts are
isolated from the internal metal motor components with
protecting insulation. Double insulated tools do not need
to be grounded.
When using a power tool at a considerable distance from
a power source, be sure to use an extension cord that has
the capacity to handle the current the tool will draw. An
undersized cord will cause a drop in line voltage, resulting in
overheating and loss of power. Use the chart to determine
the minimum wire size required in an extension cord. Only
round jacketed cords listed by Underwriter’s Laboratories
(UL) should be used.
WARNING:
When working outdoors with a tool, use an extension cord
that is designed for outside use. This type of cord is desig-
nated with “WA” on the cord’s jacket.
The double insulated system is intended to protect
the user from shock resulting from a break in the tool’s
internal insulation. Observe all normal safety precautions
to avoid electrical shock.
Before using any extension cord, inspect it for loose or
exposed wires and cut or worn insulation.
NOTE: Servicing of a tool with double insulation requires
extreme care and knowledge of the system and should be
performedonlybyaqualifiedservicetechnician. Forservice,
we suggest you return the tool to your nearest authorized
service center for repair. Always use original factory replace-
ment parts when servicing.
**Ampere rating (on tool data plate)
0-2.0
2.1-3.4 3.5-5.0 5.1-7.0 7.1-12.0 12.1-16.0
Cord Length
Wire Size (A.W.G.)
25´
50´
16
16
16
16
16
16
16
16
14
16
14
12
14
14
10
14
12
—
100´
ELECTRICAL CONNECTION
**Used on 12 gauge - 20 amp circuit.
NOTE: AWG = American Wire Gauge
This tool has a precision-built electric motor. It should be
connected to a power supply that is 120 volts, 60 Hz, AC
only (normal household current). Do not operate this tool
on direct current (DC). A substantial voltage drop will cause
a loss of power and the motor will overheat. If your tool does
not operate when plugged into an outlet, double-check the
power supply.
WARNING:
Keep the extension cord clear of the working area.
Position the cord so that it will not get caught on lumber,
tools or other obstructions while you are working with a
power tool. Failure to do so can result in serious personal
injury.
WARNING:
Check extension cords before each use. If damaged
replace immediately. Never use tool with a damaged cord
since touching the damaged area could cause electrical
shock resulting in serious injury.
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FEATURES
PRODUCT SPECIFICATIONS
Chuck Capacity..............................................................................................................................................5/64 in. - 1/2 in.
Hammer Speed ...................................................................................................................................Low (0 - 16,000 BPM*)
High (0 - 48,000 BPM*)
No Load Speed .......................................................................................................................................Low (0 - 1,000/min.)
High (0 - 3,000/min.)
Input ....................................................................................................................................120 V, 60 Hz, AC only, 5.5 Amps
Net Weight................................................................................................................................................................. 5.75 lbs.
*Blows Per Minute
MODE
DEPTH
SELECTOR
GAUGE ROD
LOCK-ON
BUTTON
SWITCH
TRIGGER
AUXILIARY
HANDLE
ASSEMBLY
CHUCK
Fig. 1
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FEATURES
KNOW YOUR HAMMER DRILL
LOCK-ON BUTTON
The hammer drill contains a lock-on feature that allows you
to lock the drill on when you operate it continuously for
extended periods of time.
See Figure 1.
Before attempting to use this product, familiarize yourself
with all operating features and safety rules.
AUXILIARY HANDLE ASSEMBLY
MODE SELECTOR
An auxiliary handle assembly is installed onthe hammer drill.
For ease of operation, you may use the handle with either
your left hand or your right hand.
You can change the drill mode depending on the type of
material in which you are drilling.
REVERSIBLE
This hammer drill allows you to reverse the drill rotation. You
can control the direction of the chuck with a lever located
above the switch trigger.
CHUCK KEY
A chuck key is provided for use when installing or removing
bits. It is also used when removing the chuck.
DEPTH GAUGE ROD
SWITCH TRIGGER
A depth gauge rod is installed on the hammer drill to assist
you in controlling the depth of drilled holes.
The hammer drill has a conveniently located switch
trigger.
ERGONOMIC DESIGN
VARIABLE SPEED
This hammer drill is designed for comfort and ease of
grasp when operating in different positions and at different
angles.
This tool has a variable speed switch that delivers higher
speed with increased trigger pressure. Speed is controlled
by the amount of switch trigger depression.
GRIPZONE™ OVERMOLD TECHNOLOGY
The hammer drill features Gripzone™ overmold technology
for improved comfort with a positive grip.
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ASSEMBLY
UNPACKING
This product has been shipped completely assembled.
WARNING:
If any parts are missing do not operate this tool until the
missing parts are replaced. Failure to heed this warning
could result in possible serious personal injury.
n Carefully remove the tool and any accessories from the
box. Make sure that all items listed in the packing list are
included.
n Inspect the tool carefully to make sure no breakage or
damage occurred during shipping.
WARNING:
n Do not discard the packing material until you have care-
Do not attempt to modify this tool or create accesso-
ries not recommended for use with this tool. Any such
alteration or modification is misuse and could result in a
hazardous condition leading to possible serious personal
injury.
fully inspected and satisfactorily operated the tool.
n If any parts are damaged or missing, please call
1-800-525-2579 for assistance.
PACKING LIST
Hammer Drill
WARNING:
Carrying Case
Do not connect to power supply until assembly is
complete. Failure to comply could result in accidental
starting and possible serious personal injury.
Operator’s Manual
Warranty Registration Card
OPERATION
APPLICATIONS
WARNING:
You may use this tool for the purposes listed below:
nHammer drilling in concrete, brick, or other masonry
nDrilling in wood
Do not allow familiarity with tools to make you care-
less. Remember that a careless fraction of a second is
sufficient to inflict serious injury.
nDrilling in ceramics, plastics, fiberglass, and laminates
nDrilling in both soft and hard metals
WARNING:
nUsing driving accessories such as driving screws with
Always wear safety goggles or safety glasses with side
shields when operating power tools. Failure to do so
could result in objects being thrown into your eyes
resulting in possible serious injury.
screwdriver bits
nMixing paint
WARNING:
Do not use any attachments or accessories not
recommended by the manufacturer of this tool. The use
of attachments or accessories not recommended can
result in serious personal injury.
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OPERATION
WARNING:
CHUCK JAWS
Always unplug the drill before inserting or removing bits
or adjusting the auxiliary handle assembly or depth gauge
rod. Failure to unplug the tool could result in accidental
starting causing possible serious injury.
INSERTING BITS
See Figure 2.
nUnplug the hammer drill.
DRILL BIT
nPosition the chuck jaws so that the opening is slightly
larger than the drill bit you intend to use.
NOTE: To open the chuck jaws, turn the chuck collar
counterclockwise. To close the chuck jaws, turn the chuck
collar clockwise.
CHUCK COLLAR
RIGHT
nRaise the front of the drill to keep the drill bit from falling
out of the chuck jaws.
Fig. 2
WARNING:
Do not insert a drill bit into the chuck jaws and tighten
as shown in Figure 3. This could cause the drill bit to be
thrown from the drill, resulting in possible serious injury
or damage to the chuck.
nInsert the drill bit completely into the chuck.
nTighten the chuck jaws securely on the drill bit using the
chuck key provided. Do not use a wrench to tighten or
loosen the chuck jaws.
REMOVING BITS
nUnplug the hammer drill.
nLoosen the chuck jaws using the chuck key provided.
nRemove the drill bit from the chuck jaws.
WRONG
Fig. 3
ADJUSTING THE AUXILIARY HANDLE
ASSEMBLY
See Figure 4.
nUnplug the hammer drill.
nLoosen the handle assembly by turning the handle coun-
terclockwise.
nRemove the handle from the drill.
nRotate the handle assembly and place it on the opposite
side.
nTighten the handle assembly securely by turning the
handle clockwise.
AUXILIARY
HANDLE ASSEMBLY
HANDLE
Fig. 4
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OPERATION
ADJUSTING THE DEPTH GAUGE ROD
See Figure 5.
ADJUST DEPTH
GAUGE ROD
nUnplug the hammer drill.
nLoosen the handle assembly by turning the handle coun-
terclockwise.
nAdjust the depth gauge rod so that the drill bit extends
beyond the end of the rod to the required drilling depth.
nTighten handle assembly by turning handle clockwise.
TO
TIGHTEN
ADJUSTING THE DRILL MODE
See Figure 6.
Use carbide-tipped bits and select hammer mode when
drilling in hard materials such as brick, tile, concrete, etc.
Select drill mode when drilling in soft materials.
nFor hammer mode: slide the mode selector to the left.
nFor drill mode: slide the mode selector to the right.
AUXILIARY
HANDLE
TO
LOOSEN
ADJUSTING THE SPEED
See Figure 7.
Fig. 5
SLIDE RIGHT FOR
DRILLING MODE
MODE
SELECTOR
CAUTION:
Never change gears while the tool is running. Failure to
obey this caution could result in serious damage to the
drill.
The hammer drill has a two-speed knob that provides a high
speed of approximately 3,000 RPM and a low speed of ap-
proximately 1,000 RPM (stated speeds are with the trigger
switch in the “Full-on” position).
nFor high speed: Rotate the two-speed knob clockwise,
aligning the indicator mark with the “2.”
nFor low speed: Rotate the two-speed knob counterclock-
wise, aligning the indicator mark with the “1.”
If you have difficulty changing from one gear range to the
other, turn the chuck by hand until the gears engage.
SLIDE LEFT FOR
HAMMER MODE
Fig. 6
COUNTERCLOCKWISE
TO LOW SPEED
CLOCKWISE TO
HIGH SPEED
Fig. 7
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OPERATION
TURNING THE HAMMER DRILL ON/OFF
See Figure 8.
To turn the hammer drill on and off.
nTo turn the drill on: depress the switch trigger.
nTo turn the drill off: release the switch trigger.
CHANGING THE ROTATION
See Figure 9.
The direction of the chuck is controlled by the lever located
above the switch trigger.
NOTE: The design of the switch will not permit changing
the direction of rotation while the drill is running. Release
the switch trigger and allow the drill to stop before chang-
ing its direction.
DEPRESS SWITCH TRIGGER TO
TURN HAMMER DRILL ON
Fig. 8
nFor forward rotation: Move the lever to the left.
nFor reverse rotation: Move the lever to the right.
NOTE: The hammer drill will not run unless the lever is
pushed fully to the left or right.
FORWARD
ROTATION
CAUTION:
The hammer drill is not designed for reverse hammer-
ing. Failure to heed this caution may result in damage
to the drill.
REVERSE
ROTATION
LOCKING ON
Fig. 9
LOCK-ON
See Figure 10.
The lock-on feature allows you to lock the drill on when
you operate it continuously for extended periods of time. If
you have the “lock-on” feature engaged during use and the
drill is disconnected from the power supply, disengage the
“lock-on” feature immediately. Also, do not lock the trigger
switch if you might need to suddenly stop the drill.
BUTTON
WARNING:
Before connecting the hammer drill to a power supply,
make sure it is not in the “locked-on” position. Failure to
do so could result in accidental starting of the drill result-
ing in possible serious injury.
SWITCH
TRIGGER
Fig. 10
To lock on:
nDepress the switch trigger.
nPush in the lock-on button.
nRelease the switch trigger.
nRelease the lock-on button.
NOTE: To release the lock, depress the switch trigger.
13
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OPERATION
DRILLING
See Figure 11.
nDepress and release the switch trigger to make sure the
drill is in the OFF position before connecting it to a power
supply.
nCheck the rotation lever for the correct setting. Refer to
“CHANGING THE ROTATION” earlier in this manual.
nSecure the material to be drilled in a vise or with clamps
to keep it from turning as the drill bit rotates.
nPlug the hammer drill into a power supply.
nHold the drill firmly and place the bit at the point to be
drilled.
nDepress the switch trigger to start the drill.
nMove the drill bit into the workpiece, applying only enough
pressure to keep the bit cutting.
NOTE: Do not force the drill or apply side pressure to
elongate a hole. Let your drill and bit do the work.
WARNING:
Be prepared for binding at bit breakthrough. When these
situations occur, the drill has a tendency to grab and
kick in the opposite direction and could cause loss of
control when breaking through material. If you are not
prepared, this loss of control could result in possible
serious injury.
Fig. 11
HELPFUL TIPS
nWhen drilling metals, use a light oil on the drill to keep
it from overheating. The oil will prolong the life of the bit
and increase the drilling action.
nWhen drilling hard, smooth surfaces, use a center punch
to mark the desired hole location. This measure will pre-
vent the drill bit from slipping off center as you start the
hole. However, the variable speed feature allows you to
start holes without center punching. To accomplish this,
operate the drill at a low speed until you start the hole.
nIf the bit jams in the workpiece or if the drill stalls, stop
the tool immediately. Remove the bit from the workpiece
and determine the reason for jamming.
MAINTENANCE
GENERAL MAINTENANCE
WARNING:
Avoid using solvents when cleaning plastic parts. Most
plastics are susceptible to damage from various types of
commercial solvents and may be damaged by their use. Use
clean cloths to remove dirt, dust, oil, grease, etc.
When servicing, use only identical Ryobi replacement
parts. Use of any other parts may create a hazard or
cause product damage.
WARNING:
WARNING:
Do not at any time let brake fluids, gasoline, petroleum-
based products, penetrating oils, etc., come in contact
with plastic parts. Chemicals can damage, weaken or
destroy plastic which may result in serious personal
injury.
Always wear safety goggles or safety glasses with side
shields during power tool operation or when blowing
dust. If operation is dusty, also wear a dust mask.
14
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MAINTENANCE
Electrictoolsusedonfiberglassmaterial,wallboard,spackling
MALLET
compounds, or plaster are subject to accelerated wear and
possible premature failure because the fiberglass chips and
grindings are highly abrasive to bearings, brushes, commu-
tators,etc.Consequently,wedonotrecommendedusingthis
toolforextendedworkonthesetypesofmaterials. However,
if you do work with any of these materials, it is extremely
important to clean the tool using compressed air.
CHUCK
JAWS
LUBRICATION
All of the bearings in this tool are lubricated with a sufficient
amount of high grade lubricant for the life of the unit under
normal operating conditions. Therefore, no further lubrica-
tion is required.
CHUCK
HEX KEY
Fig. 12
REMOVING THE CHUCK
See Figures 12 - 14.
nUnplug the hammer drill.
SCREWDRIVER
WARNING:
Failure to unplug the tool could result in accidental start-
ing causing possible serious injury.
nOpen the chuck jaws by turning the chuck collar coun-
terclockwise.
nInsert a 5/16 in. or larger hex key into the chuck.
nTighten the chuck jaws using the chuck key provided.
Fig. 13
nLoosen the chuck screw by tapping the hex key sharply
with a mallet in a clockwise direction.
MALLET
nOpen the chuck jaws and remove the hex key.
nRemove the chuck screw by turning it in a clockwise
direction with a screwdriver.
NOTE: The screw has left hand threads.
nReinsert the hex key into the chuck.
nTighten chuck jaws securely using chuck key provided.
nLoosen the chuck by tapping the hex key sharply with a
mallet in a counterclockwise direction.
nUnscrew the chuck by hand.
HEX KEY
TIGHTENING A LOOSE CHUCK
See Figures 12 - 13.
CHUCK JAWS
The chuck may become loose on the spindle and begin
to shake when using the drill. Also, the chuck screw may
become loose, causing the chuck jaws to bind and prevent
them from closing. To tighten the chuck:
CHUCK
Fig. 14
nTap the hex key sharply with a mallet in a clockwise
nUnplug the hammer drill.
direction to tighten the chuck on the spindle.
nOpen the chuck jaws by turning the chuck collar coun-
nOpen the chuck jaws and remove the hex key.
terclockwise.
nTighten the chuck screw by turning it in a counterclock-
nInsert a 5/16 in. or larger hex key into the chuck.
wise direction with a screwdriver.
nTighten the chuck jaws using the chuck key provided.
NOTE: The screw has left hand threads.
15
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OPERATOR’S MANUAL
1/2 in. HAMMER DRILL
VARIABLE SPEED
DOUBLE INSULATED
D551H
• SERVICE
Now that you have purchased your tool, should a need ever exist for repair parts or
service, simply contact your nearest Ryobi Authorized Service Center. Be sure to provide
all pertinent facts when you call or visit. Please call 1-800-525-2579 for your nearest Ryobi
complete list of Authorized Service Centers.
• MODEL NO. AND SERIAL NO.
The model number of this tool will be found on a plate attached to the motor housing.
Please record the model number and serial number in the space provided below.
• HOW TO ORDER REPAIR PARTS
When ordering repair parts, always give the following information:
D551H
• MODEL NUMBER
• SERIAL NUMBER
RYOBI TECHNOLOGIES, INC.
1428 Pearman Dairy Road, Anderson, SC 29625
Post Office Box 1207, Anderson, SC 29622-1207
Phone 1-800-525-2579
983000-633
1-05
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