Jet J-4421-2 Service manual

Operating Instructions and Parts Manual
20-inch Disc Grinder
Models J-4421-2 and J-4421-4
WALTER MEIER (Manufacturing) Inc.
427 New Sanford Road
LaVergne, Tennessee 37086 Part No. M-577010
Ph.: 800-274-6848 Revision B 09/2013
www.waltermeier.com Copyright © 2013 Walter Meier (Manufacturing) Inc.

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1.0 Warranty and Service
Walter Meier (Manufacturing) Inc., warrants every product it sells. If one of our tools needs service or repair, one of
our Authorized Service Centers located throughout the United States can give you quick service. In most cases, any
of these Walter Meier Authorized Service Centers can authorize warranty repair, assist you in obtaining parts, or
perform routine maintenance and major repair on your JET® tools. For the name of an Authorized Service Center in
your area call 1-800-274-6848.
MORE INFORMATION
Walter Meier is consistently adding new products to the line. For complete, up-to-date product information, check with
your local Walter Meier distributor, or visit jettools.com.
WARRANTY
JET products carry a limited warranty which varies in duration based upon the product (MW = Metalworking, WW =
Woodworking).
WHAT IS COVERED?
This warranty covers any defects in workmanship or materials subject to the exceptions stated below. Cutting tools,
abrasives and other consumables are excluded from warranty coverage.
WHO IS COVERED?
This warranty covers only the initial purchaser of the product.
WHAT IS THE PERIOD OF COVERAGE?
The general JET warranty lasts for the time period specified in the product literature of each product.
WHAT IS NOT COVERED?
Five Year Warranties do not cover woodworking (WW) products used for commercial, industrial or educational
purposes. Woodworking products with Five Year Warranties that are used for commercial, industrial or education
purposes revert to a One Year Warranty. This warranty does not cover defects due directly or indirectly to misuse,
abuse, negligence or accidents, normal wear-and-tear, improper repair or alterations, or lack of maintenance.
HOW TO GET SERVICE
The product or part must be returned for examination, postage prepaid, to a location designated by us. For the name
of the location nearest you, please call 1-800-274-6848.
You must provide proof of initial purchase date and an explanation of the complaint must accompany the
merchandise. If our inspection discloses a defect, we will repair or replace the product, or refund the purchase price,
at our option. We will return the repaired product or replacement at our expense unless it is determined by us that
there is no defect, or that the defect resulted from causes not within the scope of our warranty in which case we will,
at your direction, dispose of or return the product. In the event you choose to have the product returned, you will be
responsible for the shipping and handling costs of the return.
HOW STATE LAW APPLIES
This warranty gives you specific legal rights; you may also have other rights which vary from state to state.
LIMITATIONS ON THIS WARRANTY
WALTER MEIER (MANUFACTURING) INC., LIMITS ALL IMPLIED WARRANTIES TO THE PERIOD OF THE
LIMITED WARRANTY FOR EACH PRODUCT. EXCEPT AS STATED HEREIN, ANY IMPLIED WARRANTIES OR
MERCHANTABILITY AND FITNESS ARE EXCLUDED. SOME STATES DO NOT ALLOW LIMITATIONS ON HOW
LONG THE IMPLIED WARRANTY LASTS, SO THE ABOVE LIMITATION MAY NOT APPLY TO YOU.
WALTER MEIER SHALL IN NO EVENT BE LIABLE FOR DEATH, INJURIES TO PERSONS OR PROPERTY, OR
FOR INCIDENTAL, CONTINGENT, SPECIAL, OR CONSEQUENTIAL DAMAGES ARISING FROM THE USE OF
OUR PRODUCTS. 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.
Walter Meier sells through distributors only. The specifications in Walter Meier catalogs are given as general
information and are not binding. Members of Walter Meier reserve the right to effect at any time, without prior notice,
those alterations to parts, fittings, and accessory equipment which they may deem necessary for any reason
whatsoever. JET® branded products are not sold in Canada by Walter Meier.

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2.0 Table of contents
Section Page
1.0 Warranty and Service.....................................................................................................................................2
2.0 Table of contents............................................................................................................................................3
3.0 Warnings........................................................................................................................................................4
3.1 Machinery General Safety Warnings..........................................................................................................4
3.2 General Electrical Cautions........................................................................................................................5
3.3 Wire Sizes..................................................................................................................................................5
3.4 Safety requirements for abrasive grinding machines.................................................................................5
4.0 General Specifications...................................................................................................................................6
5.0 Machine set-up...............................................................................................................................................7
5.1 Grinder set-up ............................................................................................................................................7
5.2 Spotting and anchoring the sander ............................................................................................................7
5.3 Checking table level ...................................................................................................................................7
6.0 Electrical.........................................................................................................................................................7
6.1 Service wiring.............................................................................................................................................7
6.2 To correct disc rotation...............................................................................................................................8
6.3 Changing service voltage...........................................................................................................................8
6.4 Replacing the LVP switch cut-out coil ........................................................................................................8
6.5 Changing motor connections......................................................................................................................8
7.0 Operating Instructions....................................................................................................................................9
7.1 Applying a workpiece to the disc face........................................................................................................9
7.2 ON/OFF Switch........................................................................................................................................10
7.3 Raising and lowering the table .................................................................................................................10
7.4 Adjusting the table angle..........................................................................................................................10
7.5 Using the miter system.............................................................................................................................11
8.0 Recommended abrasives .................................................................................................................................11
9.0 Maintenance procedures .................................................................................................................................12
9.1 Removing and replacing grinding discs....................................................................................................12
9.2 Removing and replacing motor and/or drive disc.....................................................................................13
10.0 Lubrication..................................................................................................................................................14
11.0 Replacement Parts.....................................................................................................................................14
11.1.1 Motor and Trunnion – Exploded View .................................................................................................15
11.1.2 Motor and Trunnion – Parts List..........................................................................................................16

3.0 Warnings
- Misuse of this machine can cause serious injury.
- For safety, machine must be set up, used and
serviced properly.
- Read, understand and follow instructions in the
operator’s and parts manual which was shipped
with your machine.
When setting up machine:
- Always avoid using machine in damp or poorly
lighted work areas.
- Always be sure machine is securely anchored to the
floor.
- Always keep machine guards in place.
- Always put start switch in “OFF” position before
plugging in machine.
When using machine:
-Never operate with machine guards missing.
-Always wear safety glasses with side shields (See
ANSI Z87.1)
-Never wear loose clothing or jewelry.
-Never overreach — you may slip and fall into the
machine.
-Never leave machine running while you are away
from it.
-Always shut off the machine when not in use.
When servicing machine:
-Always disconnect machine from electrical power
while servicing.
-Always follow instructions in operator’s and parts
manual when changing accessory tools or parts.
-Never modify the machine without consulting Walter
Meier (Manufacturing) Inc.
Read and follow these simple rules for best results
and full benefits from your machine. Used properly,
JET machinery is among the best in design and
safety. However, any machine used improperly can
be rendered inefficient and unsafe. It is mandatory
that those who use our products be properly trained
in how to use them correctly. They should read and
understand the Operating Instructions and Parts
Manual as well as all labels affixed to the machine.
Failure to follow all of these warnings can cause
serious injuries.
3.1 Machinery General Safety Warnings
1. Always wear protective eye wear when operating
machinery. Eye wear shall be impact resistant,
protective safety glasses with side shields which
comply with ANSI Z87.1 specifications. Use of
eye wear which does not comply with ANSI
Z87.1 specifications could result in severe injury
from breakage of eye protection.
2. Wear proper apparel. No loose clothing or
jewelry which can get caught in moving parts.
Contain long hair. Rubber soled footwear is
recommended for best footing.
3. Do not overreach. Failure to maintain proper
working position can cause you to fall into the
machine or cause your clothing to get caught —
pulling you into the machine.
4. Keep guards in place and in proper working
order. Do not operate the machine with guards
removed.
5. Avoid dangerous working environments. Do not
use stationary machine tools in wet or damp
locations, or in an explosive environment. Keep
work areas clean and well lit. Special electrics
should be used when working on flammable
materials.
6. Avoid accidental starts by being sure the start
switch is “OFF” before plugging in the machine.
7. Machinery must be anchored to the floor.
8. Never leave the machine running while
unattended. Machine shall be shut off whenever
it is not in operation.
9. Disconnect electrical power before servicing.
Whenever changing accessories or general
maintenance is done on the machine, electrical
power to the machine must be disconnected
before work is done.
10. Maintain all machine tools with care. Follow all
maintenance instructions for lubricating and the
changing of accessories. No attempt shall be
made to modify or have makeshift repairs done
to the machine. This not only voids the warranty
but also renders the machine unsafe.
11. Secure work. Use clamps or a vise to hold work,
when practical. It is safer than using your hands
and it frees both hands to operate the machine.
12. Never brush away chips while the machine is in
operation.
13. Keep work area clean. Cluttered areas invite
accidents.
14. Remove adjusting keys and wrenches before
turning machine on.
15. Use the right tool. Don’t force a tool or
attachment to do a job for which it was not
designed.
16. Use only recommended accessories and follow
manufacturer’s instructions pertaining to them.
17. Keep hands in sight and clear of all moving parts
and cutting surfaces.
18. All visitors should be kept a safe distance from
the work area. Make workshop completely safe

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by using padlocks, master switches, or by
removing starter keys. 19. Know the tool you are using; its application, limitations, and potential hazards.
3.2 General Electrical Cautions
This machine should be grounded in accordance
with the National Electrical Code and local codes
and ordinances. This work should be done by a
qualified electrician. The machine should be
grounded to protect the user from electrical shock.
3.3 Wire Sizes
Caution: For circuits which are far away from the
electrical service box, the wire size must be
increased in order to deliver ample voltage to the
motor. To minimize power losses and to prevent
motor overheating and burnout, the use of wire
sizes for branch circuits or electrical extension
cords according to the following table is
recommended:
Conductor
Length AWG Number
240 Volt Lines 120 Volt Lines
0 – 50 Ft. No. 14 No. 14
50 – 100 Ft. No. 14 No. 12
Over 100 Ft. No. 12 No. 8
3.4 Safety requirements for abrasive grinding machines
Abrasive grinding can be hazardous to operators and
bystanders. Grinding sparks, chips and dust particles
thrown off by the grinding disc can cause serious
injury by contact or inhalation. To avoid such injuries
you must comply with the following safety
requirements:
1. CAUTION: The gap between the abrasive
surface and table edge must not exceed 3/16". If
it does, loosen the four motor mount bolts and
move the motor forward to minimize gap.
2. Always wear protective eyewear when operating
machinery. Eye wear shall be impact resistant,
protective safety glasses with side shields which
comply with ANSIZ87.1. Use of eye wear which
does not comply with ANSIZ87.1 specifications
could result in severe injury from breakage of
eye protection. See Figure A, below.
3. Wear leather safety gloves, arm guards, leather
aprons and safety shoes.
4. A dust collection system is recommended.
Operator shall also wear a dust mask at all
times. See Figure B, below.
5. Additional precautions may be necessary for
grinding materials which are flammable or have
other hazardous properties. You should always
consult the manufacturer of such materials for
instructions on grinding and handling.
6. Do not force or jamb the workpiece into the
grinding disc.
7. Before grinding, always allow the motor to come
up to operating speed, then check the grinding
disc for wobble, runout, or any unbalanced
condition. If the disc is not operating accurately
and smoothly, immediately stop the motor and
make repairs before attempting any grinding
operations.
8. Abrasive discs must be stored in a controlled
environment area. Relative humidity should be
35% to 50% and the temperature should be
between 60 and 80 degrees Fahrenheit. Failure
to do so could cause premature disc failure.
9. Examine the face of the grinding disc carefully.
Excessive grinding which wears down to the
backing material can result in tearing of the disc.
Never use a disc which shows backing, nicks or
cuts on the surface or edge or damage due to
creasing or poor handling.
10. When installing a new disc, be certain the disc is
accurately centered on the drive wheel. Failure
to do so could cause a serious unbalanced
condition.
11. Always present the workpiece to the wheel while
resting the workpiece firmly on the table. Failure
to do so could result in damage to the workpiece
or throwing of the workpiece off the wheel.
12. Safety shoes which comply with ANSI Z41.1
shall be worn. See Figure C.
13. Personal hearing protection such as ear plugs or
earmuffs shall be used to protect against the
effect of noise exposure. See Figure D.

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4.0 General Specifications
The JET Model J-4421 20-inch diameter disc grinder is a high production, rapid stock removal tool. The stock
removal rate is controlled by the amount of pressure the operator applies to the work piece and the grit of the
abrasive sheet mounted on the drive disc. By using different grit values and materials, a wide range of
materials can be ground and an equally wide range of surface finishes achieved.
Because the Model J-4421 is of heavy-duty design throughout, large piece parts can be ground. The use of
either the miter system or the tilt table allows high production grinding of angles. When used in combination,
the miter/tilt design allows the grinding of compound angles.
The table tilt mechanism is a rigid, precision worm-and-sector gear controlled with a crank. Table angle is
shown on a protractor mechanism.
Table height with respect to the drive disc can be adjusted using a rack and pinion gear system controlled by a
crank. The table assembly is counterbalanced to make raising and lowering the table easier and to increase the
service life of the lifting components.
Model number.......................................................................J-4421-2.....................................................J-4421-4
Stock numbers........................................................................577010.......................................................577011
..................................................................................(prewired 220V)......................................... (prewired 440V)
Motor....................................................................................................... TEFC, 3HP, 3PH, 220/440V, 1725 RPM
Table size....................................................................................................27-1/2 x 10-1/2 in. (68.75 x 26.25 cm)
Table slot.......................................................................................................................3/8 x 3/4 in. (9.3 x 19 mm)
Table tilt...............................................................................................45 degrees downward; 15 degrees upward
Overall dimensions.............................................................................30 x 27-1/2 x 53 in. (75 x 68.75 x 132.5 cm)
Net weight .......................................................................................................................................397 lb (180 kg)
Shipping weight...............................................................................................................................529 lb (240 kg)
The specifications in this manual were current at time of publication, but because of our policy of continuous
improvement, Walter Meier (Manufacturing) Inc., reserves the right to change specifications at any time and without
prior notice, without incurring obligations.

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5.0 Machine set-up
5.1 Grinder set-up
1. Uncrate the grinder and remove it from its
shipping skid.
2. Remove the table raiser crank which is taped
to the grinder and install the crank on the
raiser shaft, securing it with the set screw in
the crank.
3. Spot and anchor the grinder according to
instructions in the next section.
4. Remove the grinding disc (which is in a
protective sleeve) from the machine.
5. Clean the protective coating on the machine
surfaces with mineral spirits or other type of
non-flammable cleaning fluid.
6. Clean the surface of the drive disc using a film-
free cleaner such as naptha.
7. Remove the grinding disc from its protective
sleeve and install it on the drive disc according
to instructions in sect. 9.1 Removing and
replacing grinding discs.
8. Tilt the table to level using the protractor on
the table, then raise the table assembly until it
is more-or-less in the middle of the drive disc.
9. Check table for level according to instructions
following in this section.
10. Establish power to the grinder using
instructions in sect. 6.0 Electrical which follow
in this section.
11. Grinder may be released for service.
Figure 1: Base hold-down diagram
5.2 Spotting and anchoring the
sander
1. Set 3/8 inch floor anchors in the pattern
indicated in Figure 1.
2. Set the grinder on its anchors.
3. Level the table using the protractor on the
table.
4. Put a machinist's level on the table.
5. Use the two leveling bolts on the rear of the
base to level the grinder. Shim under the
anchor positions as needed to level the
grinder.
6. Secure the grinder to the floor using the
anchors.
5.3 Checking table level
While the machine has been run at the factory and
checked before shipment, you may want to check
the table level before releasing the grinder for
service.
1. Disconnect the grinder from its electrical power
source to prevent accidental start-up (if you
have already connected it to power.)
2. Unlock the table tilt lock handle.
3. Place a machinist's square against the table
and disc face.
4. Using the table tilt adjustment handle, adjust
the table until it is at a right angle to the disc
face.
5. Check the protractor pointer. It should be on
the ZERO degree mark of the protractor. If not,
adjust the pointer by loosening its attachment
screw and moving it to the ZERO mark, then
retighten the screw.
6.0 Electrical
The Model J-4421 has a 220/440 Volt, 3-phase
motor. It is shipped wired to the specifications on
the customer order.
The machine uses a LVP or "low voltage
protection" ON/OFF switch which trips to the OFF
position when voltage drops below a pre-
determined safe level. This feature protects the
operator from a quick re-start when service voltage
cuts out or varies excessively. After tripping, the
LVP switch must be positively reset by the operator
before the motor receives power.
The LVP switch has a coil inside its case which is
designed to work with a specific voltage level. If
you decide to change the voltage source to the
grinder from 220 to 440 (or the reverse) this coil
must be replaced (in addition to changing the
motor's internal wiring connections.)
6.1 Service wiring
1. Disconnect and lock out power to the service
branch you are going to use to power the
grinder.
2. Connect the branch ground wire to the ground
wire in the cable. The ground wire in the cable
will be either green, or green with a white
trace.
3. Connect the three power wires to the three
power wires in the cable.

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4. Reestablish power to the service branch for
the grinder.
5. Turn on the grinder using the ON/OFF switch
and observe the direction of rotation of the
drive disc. It should be turning CLOCKWISE
when viewed from the front. If it is turning
clockwise, the grinder is correctly connected
and can be placed in service. If the disc is not
turning clockwise, the electrical connections
are hooked up backward and need to be
corrected.
Figure 2: Service wiring diagram
6.2 To correct disc rotation
1. Disconnect and lock out power to the service
branch for the grinder.
2. Switch any two of the three power wires to the
machine service cable.
3. Re-establish power in the service branch and
turn the grinder ON, again. The drive disc
should now be rotating in a clockwise direction
and the machine can be released for service.
6.3 Changing service voltage
As indicated in the previous section, the grinder is
shipped wired for the voltage specified on the
customer order. If you decide to change the
voltage in the service branch to the grinder (from
220 to 440 volts, or 440 to 220 volts) the electrical
connections inside the motor must be changed to
reflect the change in voltage, and the LVP switch
cut-out coil must also be changed to reflect the
new voltage requirement.
6.4 Replacing the LVP switch cut-out
coil
1. Be certain the power in the service branch to
the machine is disconnected and locked out.
2. Open the switch case by removing the two
cover screws.
3. Locate the cut-out coil which is under the
switch. See Figure 3 for position and
removal/installation motion.
Figure 3: Cut-out coil removal and replacement
4. The cut-out coil is a "snap fit" under the switch
mechanism, and is removed by pushing it to
the rear of its mount and snapping it out of its
retainer.
5. Remove the connectors which secure the coil
to the switch mechanism.
6. Connect the new cut-out coil to the switch at
the same connectors as the removed coil.
7. Insert the new coil by pushing it to the back of
its seat and snapping it into position under its
retainers.
8. Reinstall the switch cover to the switch base
using the two retainer screws.
9. Proceed to the next step – changing the motor
connections.
6.5 Changing motor connections
10. Again, be certain the power in the service
branch to the machine is disconnected and
locked out.
11. Open the electrical connection cover plate on
the motor.
12. A wiring diagram for the motor is shown in
Figure 4, and will also be on a label
underneath the motor plate cover.
13. Switch the connectors inside the motor to meet
the voltage requirements for the service
branch supplying the motor.
14. Close the motor plate cover and secure it shut
with its screws.
15. Reconnect power to the service branch and
turn ON the grinder to verify that it runs
correctly, and that the disc turns
counterclockwise.

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Figure 4: Motor wiring diagram
7.0 Operating Instructions
Use the nomenclature drawing in Figure 5 for
reference when various parts and components are
described in the operations and maintenance text.
To order service parts you will find an exploded
view of the grinder in sect. 11.1.1.
Figure 5: General grinder nomenclature
7.1 Applying a workpiece to the disc
face
No matter what size, type or material workpiece
you will be grinding, there are several important
considerations you must understand if you are
going to use the Model J-4421 disc grinder
effectively.
1. Always be certain the wheel guard is
positioned over the disc edge. Materials
abraded from your workpiece will be hurled off
the wheel if the wheel guard is not in position.
2. Always allow time for the disc to come fully up
to motor speed before contacting the
workpiece to the disc. This gives you a chance
to check for possible wheel wobble (looseness
of the disc or motor, or damage from some
earlier operation) before working against the
disc.
3. This is a very powerful and aggressive
grinding device which operates at high surface
speeds. Therefore, you always want to support
the workpiece while using the work table.
"Freehand" presentation of workpiece to the
disc surface is risky to you, to the workpiece,
and to bystanders. It is not possible to
overemphasize the need to keep the
workpiece firmly on the table.
4. The safest position at which to do any grinding
is on the right hand side of the work table
where the disc is moving downward past the
work table. Whenever possible, keep the
workpiece in this area when grinding. In
addition to safety, keeping the workpiece in
this area greatly increases the effectiveness of
the dust control chute and any vacuum dust
control system you might be using. See Figure
6.
Figure 6: Correct table work area
5. The speed and aggressiveness of the machine
means that CONTROL of the workpiece, by
you, is absolutely essential. ALWAYS USE
TWO HANDS to control the workpiece.
6. Because of the speed with which the disc can
grind, heat build-up on work pieces is usually
very rapid. To prevent burns and/or possible
loss of control of any workpiece:
a. Use heat resistant gloves to hold any
workpiece.
b. Where possible and appropriate, use
additional tooling or fixturing to hold the
workpiece when pressing against the grinding
disc.

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7.2 ON/OFF Switch
The ON/OFF switch is located on a post on the left
hand side of the grinder. There are two push
buttons on the switch: RED is for OFF and BLACK
is for ON. See Figure7.
The switch is a Low Voltage Protection or LVP
switch. When line voltage drops below a safe
working voltage (due to start-up of larger machines
on the electrical branch or other fluctuations in line
voltage) the switch automatically trips OFF.
The purpose of this feature is to prevent accidental
re-starts and damage to any workpieces you might
be grinding.
To restart the machine you should remove the
workpiece from the table and turn the switch ON,
again. Then wait for the motor to come up to full
speed before continuing your grinding.
Figure 7: On/Off Switch
7.3 Raising and lowering the table
For grinding most workpieces, the table should be
positioned more-or-less in the middle of the disc.
This allows you to do most of your work on the
right-hand side of the disc where downward motion
of the disc provides the safest grinding torque.
To grind larger workpieces, a larger disc surface
area can be exposed by lowering the table. This is
done as follows:
1. Turn off the ON/OFF switch and disconnect
the machine from its electrical power source to
prevent the possibility of accidental start-up.
2. Unlock the table lock handle.
3. Turn the table height handle until the table is at
a height appropriate to your workpiece size.
4. Lock the table lock handle.
5. Reconnect the machine to the electrical power
source.
Note: Never expose more of the grinding disc than
necessary to do an effective job of grinding the
workpiece. The more disc you have exposed, the
more hazardous any operation may become. And,
the more disc you have exposed, the harder it is to
control dust when using a vacuum dust control
system.
Figure 8: Table raiser system
7.4 Adjusting the table angle
The table can be adjusted downward to a
maximum angle of 45 degrees and upward to a
maximum angle of 15 degrees.
To adjust the table angle (Figure 9):
1. Be sure the ON/OFF switch is in the off
position.
2. Disconnect the machine from its electrical
power source to prevent any chance of an
accidental start-up.
3. Unlock the table lock handle.
4. Turn the table tilt handle until the pointer on
the angleprotractor is on the angle you want to
achieve.
5. Lock the table lock handle.
6. Reconnect the machine to its electrical power
source.
Figure 9: Table tilt system