Not all the accessories illustrated or described are included in standard delivery.
Compact Circular Saw WX429
TECHNICAL DATA
Type WX429 (4-designation of machinery, representative of Saw)
Voltage
Rated power400W
No load (rated) speed3800/min
Blade size TCT blade120mmx1.2mmx9.5mmx24T
HCS blade115mm X 1mm X 9.5mm X 60T
Diamond disc115mmx1.6mmx9.5mmx60G
Bevel capacity0-45°
Cutting capacityCutting Depth at 90° 46mm
Cutting Depth at 45°30mm
Arbor Size9.5mm
Recommended maximum material
thickness
PVC pipe (diameter) 46mm
8
Saw blade thicknessTCT blade
Spindle thread size
Protection class
Bare tool weight
Wood46mm
Aluminum 2.5mm
Tile 12mm
Sheet steel 0.5mm
HCS blade
Diamond disc
230–240V~50Hz
0.8mm
1mm
1mm
M5
/ll
2kg
NOISE INFORMATION
A weighted sound pressure LpA: 83dB(A)
A weighted sound power LwA: 93dB(A)
KpA& KwA 3.0dB(A)
Wear ear protection.
Compact Circular Saw WX429
VIBRATION INFORMATION
Vibration total values (triax vector sum) determined according to EN 60745:
Cutting wood: a
Uncertainty K = 1.5m/s²
Vibration emission value:
The declared vibration total value may be used for comparing one tool with another, and may
also be used in a preliminary assessment of exposure.
WARNING: The vibration emission value during actual use of the power tool can differ
from the declared value depending on the ways in which the tool is used dependant on the
following examples and other variations on how the tool is used:
How the tool is used and the materials being cut or drilled.
The tool being in good condition and well maintained
The use the correct accessory for the tool and ensuring it is sharp and in good condition.
The tightness of the grip on the handles and if any anti vibration accessories are used.
And the tool is being used as intended by its design and these instructions.
Cutting metal: a
Uncertainty K = 1.5m/s²
Cutting tile: a
Uncertainty K = 1.5m/s²
= 2.55m/s2
h,W
= 3.00m/s
h,M
= 4.93m/s2
h,T
2
This tool may cause hand-arm vibration syndrome if its use is not adequately managed.
WARNING: To be accurate, an estimation of exposure level in the actual conditions of use
should also take account of all parts of the operating cycle such as the times when the tool
is switched off and when it is running idle but not actually doing the job. This may significantly
reduce the exposure level over the total working period.
Helping to minimise your vibration exposure risk.
ALWAYS use sharp chisels, drills and blades.
Maintain this tool in accordance with these instructions and keep well lubricated (where appropriate).
If the tool is to be used regularly then invest in anti vibration accessories.
Avoid using tools in temperatures of 10°C or less.
Plan your work schedule to spread any high vibration tool use across a number of days.
We recommend that you purchase your accessories from the same store that sold you the tool.
Use good quality accessories marked with a well-known brand name. Choose the type according
to the work you intend to undertake. Refer to the accessory packaging for further details. Store
personnel can assist you and offer advice.
9
Compact Circular Saw WX429
GENERAL POWER TOOL
SAFETY WARNINGS
WARNING! Read all safety warnings
and all instructions. Failure to follow
the warnings and instructions may result in
electric shock, fire and/or serious injury.
suitable for outdoor use reduces the risk of
electric shock.
f) If operating a power tool in a damp
location is unavoidable, use a residual
current device (RCD) protected
supply. Use of an RCD reduces the risk of
electric shock.
Save all warnings and instructions for
future reference.
The term “power tool” in the warnings refers
to your mains-operated (corded) power tool or
battery-operated (cordless) power tool.
1. WORK AREA SAFETY
a) Keep work area clean and well lit.
Cluttered or dark areas invite accidents.
b) Do 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.
c) Keep children and bystanders
away while operating a power tool.
10
Distractions can cause you to lose control.
2. ELECTRICAL SAFETY
a) Power tool plugs must match the
outlet. Never modify the plug in any
way. Do not use any adapter plugs
with earthed (grounded) power tools.
Unmodified plugs and matching outlets
will reduce risk of electric shock.
b) Avoid body contact with earthed or
grounded surfaces, such as pipes,
radiators, ranges and refrigerators.
There is an increased risk of electric shock
if your body is earthed or grounded.
c) Do not expose power tools to rain or
wet conditions. Water entering a power
tool will increase the risk of electric shock.
d) Do not abuse the cord. Never use
the cord for carrying, pulling or
unplugging the power tool. Keep cord
away from heat, oil, sharp edges or
moving parts. Damaged or entangled
cords increase the risk of electric shock.
e) When operating a power tool
outdoors, use an extension cord
suitable for outdoor use. Use of a cord
3. PERSONAL SAFETY
a) Stay alert, watch what you are
doing and use common sense when
operating a power tool. Do not use
a power tool while you are tired or
under the influence of drugs, alcohol
or medication. A moment of inattention
while operating power tools may result in
serious personal injury.
b) Use personal protective equipment.
Always wear eye protection. Protective
equipment such as dust mask, nonskid safety shoes, hard hat, or hearing
protection used for appropriate conditions
will reduce personal injuries.
c) Prevent unintentional starting. Ensure
the switch is in the off-position
before connecting to power source
and/or battery pack, picking up or
carrying the tool. Carrying power
tools with your finger on the switch or
energising power tools that have the
switch on invites accidents.
d) Remove any adjusting key or wrench
before turning the power tool on. A
wrench or a key left attached to a rotating
part of the power tool may result in
personal injury.
e) Do not overreach. Keep proper
footing and balance at all times. This
enables better control of the power tool in
unexpected situations.
f) Dress properly. Do not wear loose
clothing or jewellery. Keep your
hair, clothing and gloves away from
moving parts. Loose clothes, jewellery or
long hair can be caught in moving parts.
g) If devices are provided for the
connection of dust extraction and
collection facilities, ensure these are
connected and properly used. Use of these
devices can reduce dust-related hazards.
Compact Circular Saw WX429
4. POWER TOOL USE AND CARE
a) Do not force the power tool. Use
the correct power tool for your
application. The correct power tool will
do the job better and safer at the rate for
which it was designed.
b)
Do not use the power tool if the switch
does not turn it on and off. Any power
tool that cannot be controlled with the
switch is dangerous and must be repaired.
c) Disconnect the plug from the power
source and/or the battery pack from
the power tool before making any
adjustments, changing accessories,
or storing power tools. Such preventive
safety measures reduce the risk of starting
the power tool accidentally.
d)
Store idle power tools out of the
reach of children and do not allow
persons unfamiliar with the power
tool or these instructions to operate
the power tool. Power tools are
dangerous in the hands of untrained users.
e) Maintain power tools. Check for
misalignment or binding of moving
parts, breakage of parts and any
other condition that may affect the
power tool’s operation. If damaged,
have the power tool repaired before
use. Many accidents are caused by poorly
maintained power tools.
f)Keep cutting tools sharp and clean.
Properly maintained cutting tools with
sharp cutting edges are less likely to bind
and are easier to control.
g) Use the power tool, accessories
and tool bits etc. in accordance
with these instructions, taking into
account the working conditions and
the work to be performed. Use of the
power tool for operations different from
those intended could result in a hazardous
situation.
5. SERVICE
a) Have your power tool serviced by
a qualified repair person using only
identical replacement parts. This will
ensure that the safety of the power tool is
maintained.
SAFETY INSTRUCTIONS
FOR ALL SAWS
a) DANGER: Keep hands away from
cutting area and the blade. Keep
your second hand on auxiliary handle,
or motor housing . If both hands are
holding the saw, they cannot be cut by the
blade.
b) Do not reach underneath the
workpiece. The guard cannot protect you
from the blade below the workpiece.
c) Adjust the cutting depth to the
thickness of the workpiece. Less than
a full tooth of the blade teeth should be
visible below the workpiece.
d) Never hold piece being cut in your
hands or across your leg. Secure
the workpiece to a stable platform. It is
important to support the work properly to
minimize body exposure, blade binding, or
loss of control.
e) Hold the power tool by insulated
gripping surfaces only, when
performing an operation where the
cutting tool may contact hidden
wiring or its own cord. Contact with a
"live" wire will also make exposed metal
parts of the power tool "live" and could
give the operator an electric shock.
f) When ripping always use a rip fence
or straight edge guide. This improves
the accuracy of cut and reduces the chance
of blade binding.
g) Always use blades with correct size
and shape (diamond versus round) of
arbour holes. Blades that do not match
the mounting hardware of the saw will run
eccentrically, causing loss of control.
h) Never use damaged or incorrect blade
washers or bolt. The blade washers and
bolt were specially designed for your saw,
for optimum performance and safety of
operation.
11
Compact Circular Saw WX429
FURTHER SAFETY
INSTRUCTIONS FOR ALL
SAWS
Kickback causes and related warnings
- Kickback is a sudden reaction to a pinched,
bound or misaligned saw blade, causing an
uncontrolled saw to lift up and out of the
workpiece toward the operator.
- When the blade is pinched or bound tightly
by the kerf closing down, the blade stalls
and the motor reaction drives the unit
rapidly back toward the operator.
- If the blade becomes twisted or misaligned
in the cut, the teeth at the back edge of the
blade can dig into the top surface of the
wood causing the blade to climb out of the
kerf and jump back toward the operator.
Kickback is the result of saw misuse and/or
incorrect operating procedures or conditions
and can be avoided by taking proper
precautions as given below.
a) Maintain a firm grip on the saw and
position your arms to resist kickback
12
forces. Position your body to either
side of the blade, but not in line with
the blade. Kickback could cause the saw
to jump backwards, but kickback forces
can be controlled by the operator, if proper
precautions are taken.
b) When blade is binding, or when
interrupting a cut for any reason,
release the trigger and hold the
saw motionless in the material until
the blade comes to a complete
stop. Never attempt to remove the
saw from the work or pull the saw
backward while the blade is in motion
or kickback may occur. Investigate and
take corrective actions to eliminate the
cause of blade binding.
c) When restarting a saw in the
workpiece, center the saw blade in
the kerf and check that saw teeth are
not engaged into the material. If saw
blade is binding, it may walk up or kickback
from the workpiece as the saw is restarted.
d) Support large panels to minimize the
risk of blade pinching and kickback.
Large panels tend to sag under their own
weight. Supports must be placed under
the panel on both sides, near the line of cut
and near the edge of the panel.
e) Do not use dull or damaged blades.
Unsharpened or improperly set blades
produce narrow kerf causing excessive
friction, blade binding and kickback.
f) Blade depth and bevel adjusting
locking levers must be tight and
secure before making cut. If blade
adjustment shifts while cutting, it may
cause binding and kickback.
g) Use extra caution when sawing into
existing walls or other blind areas. The
protruding blade may cut objects that can
cause kickback.
SAFETY INSTRUCTIONS
FOR SAWS WITH INNER
PENDULUM GUARD
Lower Guard Function
a) Check lower guard for proper closing
before each use. Do not operate the
saw if lower guard does not move
freely and close instantly. Never
clamp or tie the lower guard into the
open position. If saw is accidentally
dropped, lower guard may be bent.Raise
the lower guard with the retracting handle
and make sure it moves freely and does
not touch the blade or any other part, in all
angles and depths of cut.
b) Check the operation of the lower
guard spring. If the guard and the
spring are not operating properly,
they must be serviced before use.
Lower guard may operate sluggishly due
to damaged parts, gummy deposits, or a
build-up of debris.
c) Lower guard may be retracted
manually only for special cuts such
as "plunge cuts" and "compound
cuts." Raise lower guard by retracting
handle and as soon as blade enters
the material, the lower guard must be
released. For all other sawing, the lower guard should operateautomatically.
d) Always observe that the lower guard
Compact Circular Saw WX429
is covering the blade before placing
saw down on bench or floor. An
unprotected, coasting blade will cause the
saw to walk backwards, cutting whatever is
in its path. Be aware of the time it takes for
the blade to stop after switch is released.
ADDITIONAL SAFETY
WARNING FOR TILE
CUTTING
a) The guard provided with the tool must
be securely attached to the power
tool and positioned for maximum
safety, so the least amount of wheel is
exposed towards the operator. Position
yourself and bystanders away from the
plane of the rotating wheel. The guard
helps to protect operator from broken
wheel fragments and accidental contact
with wheel.
b) Use only bonded reinforced or
diamond cut-off wheels for your
power tool. Just because an accessory
can be attached to your power tool, it does
not assure safe operation.
c) The rated speed of the accessory
must be at least equal to the
maximum speed marked on the power
tool. Accessories running faster than their
rated speed can break and fly apart.
d) Wheels must be used only for
recommended applications. For
example: do not grind with the side
of cut-off wheel. Abrasive cut-off wheels
are intended for peripheral grinding, side
forces applied to these wheels may cause
them to shatter.
e) Always use undamaged wheel flanges
that are of correct diameter for your
selected wheel. Proper wheel flanges
support the wheel thus reducing the
possibility of wheel breakage.
f) Do not use worn down reinforced
wheels from larger power tools.
Wheels intended for a larger power tool
are not suitable for the higher speed of a
smaller tool and may burst.
g) The outside diameter and the
thickness of your accessory must
be within the capacity rating of your
power tool. Incorrectly sized accessories
cannot be adequately guarded or
controlled.
h) The arbour size of wheels and flanges
must properly fit the spindle of
the power tool. Wheels and flanges
with arbour holes that do not match the
mounting hardware of the power tool will
run out of balance, vibrate excessively and
may cause loss of control.
i) Do not use damaged wheels. Before
each use, inspect the wheels for chips
and cracks. If power tool or wheel is
dropped, inspect for damage or install an
undamaged wheel. After inspecting and
installing the wheel, position yourself and
bystanders away from the plane of the
rotating wheel and run the power tool at
maximum no load speed for one minute.
Damaged wheels will normally break apart
during this test time.
j) Wear personal protective equipment.
Depending on application, use face
shield, safety goggles or safety
glasses. As appropriate, wear dust mask,
hearing protectors, gloves and shop apron
capable of stopping small abrasive or
workpiece fragments. The eye protection
must be capable of stopping flying debris
generated by various operations. The
dust mask or respirator must be capable
of filtrating particles generated by your
operation. Prolonged exposure to high
intensity noise may cause hearing loss.
k) Keep bystanders a safe distance away
from work area. Anyone entering the
work area must wear personal protective
equipment. Fragments of workpiece or of
a broken wheel may fly away and cause
injury beyond immediate area of operation.
l) Hold the power tool by insulated
gripping surfaces only, when
performing an operation where
the cutting accessory may contact
hidden wiring or its own cord. Cutting
accessory contacting a “live” wire may
make exposed metal parts of the power
tool “live” and could give the operator an
13
Compact Circular Saw WX429
electric shock.
m) Position the cord clear of the spinning
accessory. If you lose control, the cord
may be cut or snagged and your hand or
arm may be pulled into the spinning wheel.
n) Never lay the power tool down until
the accessory has come to a complete
stop. The spinning wheel may grab the
surface and pull the power tool out of your
control.
o) Do not run the power tool while
carrying it at your side. Accidental
contact with the spinning accessory could
snag your clothing, pulling the accessory
into your body.
p) Regularly clean the power tool’s
air vents. The motor’s fan will draw the
dust inside the housing and excessive
accumulation of powdered metal may
cause electrical hazards.
q) Do not operate the power tool near
flammable materials. Sparks could ignite
these materials.
r) Do not use accessories that require
14
liquid coolants. Using water or other
liquid coolants may result in electrocution
or shock.
KICKBACK AND RELATED
WARNINGS
Kickback is a sudden reaction to a pinched or
snagged rotating wheel. Pinching or snagging
causes rapid stalling of the rotating wheel
which in turn causes the uncontrolled power
tool to be forced in the direction opposite of
the wheel’s rotation at the point of the binding.
For example, if an abrasive wheel is snagged
or pinched by the workpiece, the edge of the
wheel that is entering into the pinch point can
dig into the surface of the material causing
the wheel to climb out or kick out. The wheel
may either jump toward or away from the
operator, depending on direction of the
wheel’s movement at the point of pinching.
Abrasive wheels may also break under these
conditions.
Kickback is the result of power tool misuse
and/or incorrect operating procedures or
conditions and can be avoided by taking
proper precautions as given below.
a) Maintain a firm grip on the power tool
and position your body and arm to
allow you to resist kickback forces.
Always use auxiliary handle, if provided,
for maximum control over kickback or
torque reaction during start-up. The
operator can control torque reactions or
kickback forces, if proper precautions are
taken.
b) Never place your hand near the
rotating accessory. Accessory may
kickback over your hand.
c) Do not position your body in line with
the rotating wheel. Kickback will propel
the tool in direction opposite to the wheel’s
movement at the point of snagging.
d) Use special care when working
corners, sharp edges etc. Avoid
bouncing and snagging the accessory.
Corners, sharp edges or bouncing have a
tendency to snag the rotating accessory
and cause loss of control or kickback.
e) Do not attach a saw chain,
woodcarving blade, segmented
diamond wheel with a peripheral
gap greater than 10 mm or toothed
saw blade. Such blades create frequent
kickback and loss of control.
f) Do not “jam” the wheel or apply
excessive pressure. Do not attempt
to make an excessive depth of cut.
Overstressing the wheel increases the
loading and susceptibility to twisting or
binding of the wheel in the cut and the
possibility of kickback or wheel breakage.
g) When wheel is binding or when
interrupting a cut for any reason,
switch off the power tool and hold the
power tool motionless until the wheel
comes to a complete stop. Never
attempt to remove the wheel from the cut
while the wheel is in motion otherwise
kickback may occur. Investigate and take
corrective action to eliminate the cause of
wheel binding.
h) Do not restart the cutting operation in
the workpiece. Let the wheel reach full
speed and carefully re-enter the cut. The
Compact Circular Saw WX429
wheel may bind, walk up or kickback if the
power tool is restarted in the workpiece.
i) Support panels or any oversized
workpiece to minimize the risk of
wheel pinching and kickback. Large
workpieces tend to sag under their own
weight. Supports must be placed under the
workpiece near the line of cut and near the
edge of the workpiece on both sides of the
wheel.
j) Use extra caution when making a
“pocket cut” into existing walls or
other blind areas. The protruding wheel
may cut gas or water pipes, electrical
wiring or objects that can cause kickback.
ADDITIONAL SAFETY
RULES FOR CIRCULAR SAW
1. Always wear a dust mask, hearing
protection and eye protection.
2. Only use saw blades recommended in the
specification.
3. Do not use any abrasive wheels.
4. Use only blade diameter(s) in accordance
with the markings.
15
Compact Circular Saw WX429
SYMBOLS
16
To reduce the risk of injury, user
must read instruction manual
Double insulation
Warning
Wear ear protection
Wear eye protection
Wear dust mask
Waste electrical products must not
be disposed of with household
waste. Please recycle where
facilities exist. Check with your local
authorities or retailer for recycling
advice.
Metal
Incorrect
Correct
Lock
Unlock
Diamond disc
HCS blade
TCT blade
Before any work on the machine
itself, pull the mains plug from the
socket outlet.
Wear protective gloves
Wood
Aluminium
Compact Circular Saw WX429
OPERATING INSTRUCTIONS
NOTE: Before using the tool, read the
instruction book carefully.
teeth for very fine cuts into delicate surfaces,
diamond for tile, cement board, etc.
Only use saw blades recommended.
INTENDED USE:
The tool is intended for ripping and crosscutting wood and other materials in straight
cutting lines, while resting firmly on the work
piece.
ASSEMBLY AND OPERATION
Action Figure
Mounting and Removing
the Blade
Safety switch and On/Off
trigger
Cross and Rip CuttingSee Fig. C1, C2
Parallel GuideSee Fig. D1, D2
Adjusting the Cutting
Depth
Adjusting the Cutting
Angle
Pocket /PlungeSee Fig. G1, G2
Sawdust RemovalSee Fig. H
Adjusting the Base PlateSee Fig. I
See Fig. A
See Fig. B
See Fig. E1, E2
See Fig. F
WORKING HINTS FOR YOUR
TOOL
If your power tool becomes too hot, please
run your circular saw no load for 2-3 minutes
to cool the motor. Avoid prolonged usage at
very low speeds.
Protect saw blades against impact and shock.
Cutting with extreme force can significantly
reduces the performance capability of the tool
and reduces the service life of the saw blade.
Sawing performance and cutting quality
depend essentially on the condition and the
tooth count of the saw blade. Therefore, use
only sharp saw blades that are suited for the
material being cut.
Choice of blades: 24 teeth for general work,
approx. 40 teeth for finer cuts, more than 40
MAINTAIN TOOLS WITH
CARE
Remove the plug from the socket before
carrying out any adjustment, servicing or
maintenance.
Keep tools sharp and clean for better and
safer performance. Follow instructions for
lubricating and changing accessories. Inspect
tool cords periodically and if damaged, have
repaired by authorized service facility. Your
power tool requires no additional lubrication
or maintenance. There are no user serviceable
parts in your power tool. Never use water or
chemical cleaners to clean your power tool.
Wipe clean with a dry cloth. Always store
your power tool in a dry place. Keep the
motor ventilation slots clean. Keep all working
controls free of dust.
If the supply cord is damaged, it must be
replaced by the manufacturer, its service
agent or similarly qualified persons in order to
avoid a hazard.
Periodically clear dust and chips from guard
and base to ensure proper performance.
ENVIRONMENTAL
PROTECTION
Waste electrical products must not be
disposed of with household waste.
Please recycle where facilities exist.
Check with your local authorities or retailer for
recycling advice.
17
Compact Circular Saw WX429
TROUBLE SHOOTING
SymptomPossible CausesPossible Solution
Tool will not start when
operating the on/off trigger.
Cutting depth is less than
that is set.
Blade spins or slips.
Blade will not cut a straight
line.
18
Blade kicks back when
beginning a cut.
Safety switch is not
pressed.
Power cord not plugged in.
Power cord is broken.
Carbon brush has worn
down
Sawdust accumulated at
the rear of the base.
Blade is not tightly
engaged with the spindle.
Blade is dull.
Blade is not mounted
properly.
Saw is not being guided
properly.
Saw blade teeth may be
engaged in the material
when starting.
Blade is not spinning fast
enough
Press safety switch and hold it
while engaging the on/off trigger.
Check to make sure power cord
is connected well into a working
outlet.
Unplug the power cord and
replace it using a qualified
maintenance person.
Replace the carbon brush using a
qualified maintenance person.
Shake out sawdust. Consider
connecting a vacuum for dust
collection.
Remove the blade and
reassemble it as described in
Mounting and Removing the
Blade section.
Mount a new, sharp blade on
the saw.
Check that blade is properly
mounted.
Use a parallel guide.
Before restarting a saw in the
workpiece, center the saw blade
in the kerf and check that the saw
teeth are not engaged into the
material.
Allow the saw blade to reach full
speed prior to beginning a cut in
the material.
Compact Circular Saw WX429
PLUG REPLACEMENT
( ONLY FOR REWIRABLE
PLUG OF UK & IRELAND )
If you need to replace the fitted plug then
follow the instructions below.
IMPORTANT
The wires in the mains lead are colored in
accordance with the following code:
BLUE =NEUTRAL
Brown = Live
As the colors of the wires in the mains lead of
this appliance may not correspond with the
colored markings identifying the terminals
in your plug, proceed as follows. The wire
which is colored blue must be connected to
the terminal which is marked with N. The wire
which is colored brown must be connected to
the terminal which is marked with L.
WARNING! Never connect live or neutral
wires to the earth terminal of the plug. Only
fit an approved 13ABS1363/A plug and the
correct rated fuse.
NOTE: If a moulded plug is fitted and has to
be removed take great care in disposing of the
plug and severed cable, it must be destroyed
to prevent engaging into a socket.
13 Amp fuse approved
to BS1362
Connect
Blue to N
(neutral)
Outer sleeve
firmly clamped
Brown L (live)
Cable grip
DECLARATION OF
CONFORMITY
We,
Positec Power Tools (Europe) Ltd,
PO Box 152, Leeds, LS10 9DS, UK
Declare that the product,
Description WORX Electric Circular Saw
Type WX429 (4-designation of machinery,
representative of Saw)
Function Cutting various materials with a
rotating toothed blade
Complies with the following Directives,
2006/42/EC
2004/108/EC
2011/65/EU
Standards conform to:
EN 55014-1
EN 55014-2
EN 61000-3-2
EN 61000-3-3
EN 60745-1
EN 60745-2-5
EN 60745-2-22
The person authorized to compile the technical
file,
Name: Russell Nicholson
Address: Positec Power Tools (Europe)
Ltd, PO Box 152, Leeds, LS10 9DS, UK
19
Suzhou 2015/05/20
Allen Ding
Deputy Chief Engineer,Testing &
Certification