Operation; Maintenance - DeWalt DW421 Instruction Manual

..................Class I Construction
......................(grounded)
.................Class II Construction
.....................(double insulated)
BPM .............beats per minute
Precautions To Take When Sanding Paint
1. Sanding of lead based paint is NOT RECOMMENDED due to the difficulty of controlling
the contaminated dust. The greatest danger of lead poisoning is to children and pregnant
women.
2. Since it is difficult to identify whether or not a paint contains lead without a chemical
analysis, we recommend the following precautions when sanding any paint:
PERSONAL SAFETY
1. No children or pregnant women should enter the work area where the paint sanding
is being done until all clean up is completed.
2. A dust mask or respirator should be worn by all persons entering the work area. The
filter should be replaced daily or whenever the wearer has difficulty breathing. See
your local hardware store for the proper NIOSH-approved dust mask.
3. NO EATING, DRINKING or SMOKING should be done in the work area to prevent
ingesting contaminated paint particles. Workers should wash and clean up BEFORE
eating, drinking or smoking. Articles of food, drink, or smoking should not be left in the
work area where dust would settle on them.
ENVIRONMENTAL SAFETY
1. Paint should be removed in such a manner as to minimize the amount of dust gener-
ated.
2. Areas where paint removal is occurring should be sealed with plastic sheeting of
4 mils thickness.
3. Sanding should be done in a manner to reduce tracking of paint dust outside the work
area.
CLEANING AND DISPOSAL
1. All surfaces in the work area should be vacuumed and thoroughly cleaned daily for
the duration of the sanding project. Vacuum filter bags should be changed frequent-
ly.
2. Plastic drop cloths should be gathered up and disposed of along with any dust chips
or other removal debris. They should be placed in sealed refuse receptacles and
disposed of through regular trash pick-up procedures. During clean up, children and
pregnant women should be kept away from the immediate work area.
3. All toys, washable furniture and utensils used by children should be washed thoroughly
before being used again.
SAVE THESE INSTRUCTIONS
Motor
Your D WALT tool is powered by a D
E
the nameplate marking. (Volts, 120 AC only). Voltage decrease of more than 10% will cause
loss of power and overheating. All D
E
check the power supply.
Intended Use
The DW421 heavy-duty random orbit palm sander has been designed for professional
sanding at various work sites (i.e., construction sites). DO NOT use under humid conditions
or in presence of flammable liquids or gases.
This random orbit palm sander is a professional power tool. DO NOT let children come into
contact with the tool. Supervision is required when inexperienced operators use this tool.
Attaching Sanding Discs
Your sander is designed to use 5" (127 mm) sanding discs. Discs have an 8 hole dust
extraction pattern and hook and loop attachment. To attach paper to the sanding pad:
REQUIRED SANDPAPERS
Disc
Size
5"
1. Turn off and unplug the tool.
2. Turn the sander over so that the sanding pad is facing upward.
3. Clean dust from the vinyl pad face.
4. Hold the pad with one hand to keep it from rotating.
5. With the other hand, align the holes if they are present, and place the disc directly on top
of the pad. (FIG. 1).
NOTE: Do not use sanding screen (e.g. screen used for sanding drywall) directly on the
hook and loop pad. The screen will not hold and will damage the hooks on the pad. The
hooks on the pad will wear very rapidly if left in contact with the work surface while the tool
is operating.
Switch (Fig. 2)
To turn the unit on, depress the side of the dust protected switch that corresponds to
the symbol "I". To turn the tool off, depress the side of the switch that corresponds to the
symbol "O".
Dust Extraction (Fig. 3, 4)
Your sander comes equipped with a cloth bag to collect the dust generated during sand-
ing. It was designed to be very durable and efficient yet easy to empty. To empty the dust
collection bag:
1. Turn off and unplug tool.
2. While holding the canister, twist to unlock and remove the adapter. (Fig. 3)
3. Gently empty the bag and shake out the adapter. (Fig. 4)
You may notice that all the dust will not come free from the bag. This will not affect sanding
performance but will reduce the sander's dust collection efficiency. To restore your sander's
dust collection efficiency, depress the spring inside the dust bag when you are emptying it
and tap it on the side of the trash can or dust receptacle.
CAUTION: Never operate this tool unless the dust collector is in place. Sanding dust
exhaust may create a breathing hazard.

OPERATION

WARNING: To reduce the risk of serious personal injury, turn tool off and
disconnect tool from power source before making any adjustments or removing/
installing attachments or accessories.
Usage
To operate your sander, grasp it as shown in figures 5A or 5B and turn it on. Move the unit
in long, sweeping strokes along the surface being sanded, letting the sander do the work.
Pushing down on the tool while sanding actually slows the removal rate and produces an
inferior quality surface. Be sure to check your work often, this sander is capable of removing
material rapidly, especially with coarse paper.
The random orbital action of your sander allows you to sand with the grain or at any angle
across it for most sanding jobs. To produce the best finish possible, start with coarse grit
sandpaper and change gradually to finer and finer paper. Vacuum and wipe surface with a
tack cloth between grit steps.Your sander is designed to sand into small or confined areas.
Its small size and light weight make it ideal for overhead work.
If your sander has the dust collection feature, the rate at which the dust collection bag fills
up will vary with the type of material being sanded and the coarseness of the sandpaper.
For best results, empty the bag frequently. When sanding painted surfaces, (see the follow-
ing for additional precautions when sanding paint) you may find that the sandpaper loads
up and clogs with paint. A heat gun will work much better to remove paint before sanding.
FOLLOW ALL SAFETY INSTRUCTIONS IN HEAT GUN INSTRUCTION MANUAL.

MAINTENANCE

WARNING: To reduce the risk of serious personal injury, turn tool off and
disconnect tool from power source before making any adjustments or removing/
installing attachments or accessories.
Cleaning
WARNING: Never use solvents or other harsh chemicals for cleaning the non-metallic
parts of the tool. These chemicals may weaken the plastic materials used in these parts.
Use a cloth dampened only with water and mild soap. Never let any liquid get inside the
tool; never immerse any part of the tool into a liquid.
...................earthing terminal
..................safety alert symbol
.../min .......... revolutions or reciprocation
.................... per minute
WALT built motor. Be sure your power supply agrees with
E
WALT tools are factory tested; if this tool does not operate,
Attachment Hole
Method Pattern
Hook & Loop 8 holes
FIG. 1
FIG. 3
FIG. 5A
FIG. 7
FIG. 10
Tool Care
1. Keep your sander as clean as possible by wiping with a clean cloth and blowing air
through it after every 5 hours of use.
2. As part of CFS (Controlled Finishing System), your sander is equipped with a
replaceable disc which is located between the pad and the shroud. It is designed to
increase the dust collection efficiency and control the pad speed while the unit is off the
work. The disc is designed to be a consumable part and will occasionally need to be
replaced. Replacement is necessary when the pad speed increases very dramatically
when the unit is lifted from the work surface. To replace your CFS disc:
a. Turn off and unplug tool.
b. Remove 3 screws from the bottom of the pad.
c. Remove the pad.
d. Snap out worn disc.
e. Snap in new disc, aligning notch in disc with cut out in shroud shown in figure 7.
f. Press in new disc around the edges using both hands to ensure that the disc is
inserted snugly into the shroud as shown in figure 8.
g. Replace the pad and the 3 screws.
3. Avoid overloading your sander. Overloading will result in a considerable reduction in
speed and finish quality of your work. The unit may also become hot. In this event, run
sander at a no load condition for a minute or two.
4. If you wrap the cord around the tool when you store it, leave a generous loop of cord
such that the strain relief does not bend. This helps prevent premature cord failure.
Brush Replacement
WARNING: To reduce the risk of serious personal injury, turn tool off and
disconnect tool from power source before making any adjustments or removing/
installing attachments or accessories.
Follow these directions to replace the tool's brushes:
1. Remove the three screws located in the top cap, as shown in figure 9.
2. Lift off the top cap. Observe the brush holders and wires leading from the brushes to the
motor field, as shown in figure 10.
3. Pull the wires from the motor field and then lift and hold out of the way of one of the
brush springs.
4. Remove the old brush from the brush holder and discard the brush/wire assembly. Still
holding the brush spring out of the way, insert the new brush and release the spring
against the back of the brush. Then plug the wire into the motor field. Repeat the pro-
cedure for the second brush.
5. Replace the top cap and tighten the three screws that hold it in place. Always replace
both brushes.
Lubrication
Self lubricating bearings are used in the tool and periodic relubrication is not required.
However, it is recommended that, once a year, you take or send the tool to a service center for
a thorough cleaning and inspection.
FIG. 2
FIG. 4
FIG. 5B
FIG. 8
FIG. 9