Jet 321378 Service manual

Operating Instructions and Parts Manual
9x19, 9x29-inch Belt Drive Bench Lathes
Models BDB-919, -929
JET
427 New Sanford Road
LaVergne, Tennessee 37086 Part No. M-321378
Ph.: 800-274-6848 Edition 2 12/2020
www.jettools.com Copyright © 2017 JET
For machines with serial no. after 1701178.
This .pdf document is bookmarked

2
1.0 IMPORTANT SAFETY INSTRUCTIONS
1.1 GROUNDING INSTRUCTIONS
1. All grounded, cord-connected tools:
In the event of a malfunction or breakdown, grounding provides a path of least resistance for electric current to
reduce the risk of electric shock. This tool is equipped with an electric cord having an equipment-grounding
conductor and a grounding plug. The plug must be plugged into a matching outlet that is properly installed and
grounded in accordance with all local codes and ordinances.
Do not modify the plug provided - if it will not fit the outlet, have the proper outlet installed by a qualified electrician.
Improper connection of the equipment-grounding conductor can result in a risk of electric shock. The conductor
with insulation having an outer surface that is green with or without yellow stripes is the equipment-grounding
conductor. If repair or replacement of the electric cord or plug is necessary, do not connect the equipment-
grounding conductor to a live terminal.
Check with a qualified electrician or service personnel if the grounding instructions are not completely
understood, or if in doubt as to whether the tool is properly grounded.
Use only 3-wire extension cords that have 3-prong grounding plugs and 3-pole receptacles that accept the tool's
plug.
Repair or replace damaged or worn cord immediately.
2. Grounded, cord-connected tools intended for use on a supply circuit having a nominal rating less than
150 volts:
This tool is intended for use on a circuit that has an outlet that looks like the one illustrated in Sketch A. The tool
has a grounding plug that looks like the plug illustrated in Sketch A. A temporary adapter, which looks like the
adapter illustrated in Sketches B and C, may be used to connect this plug to a 2-pole receptacle as shown in
Sketch B if a properly grounded outlet is not available. The temporary adapter should be used only until a properly
grounded outlet can be installed by a qualified electrician.(This adapter is not permitted in Canada) The green-
colored rigid ear, lug, and the like, extending from the adapter must be connected to a permanent ground such
as a properly grounded outlet box.
3. Grounded, cord-connected tools intended for use on a supply circuit having a nominal rating between
150 - 250 volts, inclusive:
This tool is intended for use on a circuit that has an outlet that looks like the one illustrated in Sketch D. The tool
has a grounding plug that looks like the plug illustrated in Sketch D. Make sure the tool is connected to an outlet
having the same configuration as the plug. No adapter is available or should be used with this tool. If the tool
must be reconnected for use on a different type of electric circuit, the reconnection should be made by qualified
service personnel; and after reconnection, the tool should comply with all local codes and ordinances.
4. Permanently connected tools:
This tool should be connected to a grounded metal permanent wiring system; or to a system having an
equipment-grounding conductor.

3
1.2 For all tools as applicable
1. READ AND UNDERSTAND the warnings posted on the machine and in this manual. Failure to comply with
all of these warnings may cause serious injury.
2. Replace the warning labels if they become obscured or removed.
3. This lathe is designed and intended for use by properly trained and experienced personnel only. If you are
not familiar with the proper and safe operation of a lathe, do not use until proper training and knowledge
have been obtained.
4. Do not use this lathe for other than its intended use. If used for other purposes, JET disclaims any real or
implied warranty and holds itself harmless from any injury that may result from that use.
5. KEEP GUARDS IN PLACE and in working order.
6. REMOVE ADJUSTING KEYS AND WRENCHES. Form habit of checking to see that keys and adjusting
wrenches are removed from tool before turning it on.
7. KEEP WORK AREA CLEAN. Cluttered areas and benches invite accidents.
8. DON'T USE IN DANGEROUS ENVIRONMENT. Don't use power tools in damp or wet locations, or expose
them to rain. Keep work area well lighted.
9. KEEP CHILDREN AWAY. All visitors should be kept safe distance from work area.
10. MAKE WORKSHOP KID PROOF with padlocks, master switches, or by removing starter keys.
11. DON'T FORCE TOOL. It will do the job better and safer at the rate for which it was designed.
12. USE RIGHT TOOL. Don't force tool or attachment to do a job for which it was not designed.
13. WEAR PROPER APPAREL. Do not wear loose clothing, gloves, neckties, rings, bracelets, or other jewelry
which may get caught in moving parts. Nonslip footwear is recommended. Wear protective hair covering to
contain long hair.
14. ALWAYS USE SAFETY GLASSES. Always wear ANSI Z87.1 approved safety glasses or face shield while
using this lathe. (Everyday eyeglasses only have impact resistant lenses; they are not safety glasses.)
15. SECURE WORK. Use clamps or a vise to hold work when practical. It's safer than using your hand and it
frees both hands to operate tool.
16. DON'T OVERREACH. Keep proper footing and balance at all times.
17. MAINTAIN TOOLS WITH CARE. Keep tools sharp and clean for best and safest performance. Follow
instructions for lubricating and changing accessories.
18. Give your work undivided attention. Looking around, carrying on a conversation and “horse-play” are
careless acts that can result in serious injury.
19. DISCONNECT TOOLS before servicing; when changing accessories, such as blades, bits, cutters, and the
like.
20. REDUCE THE RISK OF UNINTENTIONAL STARTING. Make sure switch is in off position before plugging
in.
21. USE RECOMMENDED ACCESSORIES. Consult the owner's manual for recommended accessories. The
use of improper accessories may cause risk of injury to persons.

4
22. NEVER STAND ON TOOL. Serious injury could occur if the tool is tipped or if the cutting tool is unintentionally
contacted.
23. CHECK DAMAGED PARTS. Before further use of the tool, a guard or other part that is damaged should 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.
24. DIRECTION OF FEED. Feed work into a blade or cutter against the direction of rotation of the blade or cutter
only.
25. NEVER LEAVE TOOL RUNNING UNATTENDED. TURN POWER OFF. Don't leave tool until it comes to a
complete stop.
26. Do not operate this machine while tired or under the influence of drugs, alcohol or any medication.
27. Tighten all locks before operating.
28. USE PROPER EXTENSION CORD. Make sure your extension cord is in good condition. When using an
extension cord, be sure to use one heavy enough to carry the current your product will draw. An undersized
cord will cause a drop in line voltage resulting in loss of power and overheating. Table 1 shows the correct
size to use depending on cord length and nameplate ampere rating. If in doubt, use the next heavier gage.
The smaller the gage number, the heavier the cord.
Ampere Rating
Volts Total length of cord in feet
120 V 25 ft. 50 ft. 100 ft. 150 ft.
240 V 50 ft. 100 ft. 200 ft. 300 ft.
More than
Not more
than AWG
0 6 18 16 16 14
6 10 18 16 14 12
10 12 16 16 14 12
12 16 14 12 Not recommended
Only the applicable parts of the Table need to be included. For instance, a 120-volt product need
not include the 240-volt heading.
Table 1
Minimum Gage for Cord
WARNING: This product can expose you to chemicals including lead and cadmium which are known to
the State of California to cause cancer and birth defects or other reproductive harm, and phthalates which are
known to the State of California to cause birth defects or other reproductive harm. For more information go to
http://www.p65warnings.ca.gov.
WARNING: Some dust, fumes and gases created by power sanding, sawing, grinding, drilling, welding
and other construction activities contain chemicals known to the State of California to cause cancer and birth
defects or other reproductive harm. Some examples of these chemicals are:
lead from lead based paint
crystalline silica from bricks, cement and other masonry products
arsenic and chromium from chemically treated lumber
Your risk of exposure 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 dust masks
that are specifically designed to filter out microscopic particles. For more information go to
http://www.p65warnings.ca.gov/ and http://www.p65warnings.ca.gov/wood.

5
2.0 Table of Contents
1.0 IMPORTANT SAFETY INSTRUCTIONS .......................................................................................................2
1.1 GROUNDING INSTRUCTIONS .................................................................................................................2
1.2 For all tools as applicable...........................................................................................................................3
2.0 Table of Contents...........................................................................................................................................5
3.0 Introduction ....................................................................................................................................................7
4.0 Specifications .................................................................................................................................................7
5.0 Unpacking ......................................................................................................................................................9
5.1 Contents of shipping container...................................................................................................................9
6.0 Setup and preparation for operation ............................................................................................................10
7.0 General description ......................................................................................................................................10
7.1 Lathe bed .................................................................................................................................................10
7.2 Headstock ................................................................................................................................................10
7.3 Carriage....................................................................................................................................................11
7.4 Apron........................................................................................................................................................11
7.5 Tailstock ...................................................................................................................................................12
7.6 Lead screw ...............................................................................................................................................12
7.7 Gear box...................................................................................................................................................12
7.8 Drive and electrical equipment .................................................................................................................12
8.0 Controls........................................................................................................................................................13
9.0 Operation .....................................................................................................................................................14
9.1 Tool set-up ...............................................................................................................................................14
9.2 Manual turning..........................................................................................................................................14
9.3 Longitudinal turning with auto-feed ..........................................................................................................14
9.4 Taper turning using tailstock off-set ......................................................................................................... 15
9.5 Taper turning by setting the top slide .......................................................................................................15
9.6 Turning Between Centers.........................................................................................................................15
9.7 Thread Cutting..........................................................................................................................................16
9.8 Metric Thread Cutting...............................................................................................................................16
10.0 Lathe Accessories......................................................................................................................................17
10.1 Three jaw universal lathe chuck .............................................................................................................17
10.2 Four jaw independent lathe chuck..........................................................................................................17
10.3 Drill chuck (optional)...............................................................................................................................17
10.4 Morse taper arbor (optional)...................................................................................................................17
10.5 Live center (optional)..............................................................................................................................17
10.6 Steady rest .............................................................................................................................................18
10.7 Setting the steady rest............................................................................................................................18
10.8 Follow rest ..............................................................................................................................................18
10.9 Stand (optional) ......................................................................................................................................18
10.10 Four-way tool post................................................................................................................................19
10.11 Change Gears ......................................................................................................................................19
11.0 Adjustment/replacement ................................................................................................................................19
11.1 Adjustment of main spindle bearings .....................................................................................................19
11.2 Adjustment of cross and top slide ..........................................................................................................19
11.3 Adjustment of compound feed screw and float ......................................................................................20
11.4 Cross slide screw ...................................................................................................................................20
11.5 Compound slide spindle backlash adjustment .......................................................................................20
11.6 Adjustment of half-nut guide...................................................................................................................21
11.7 Replacing the V-belt ...............................................................................................................................21
12.0 Lubrication Schedule..................................................................................................................................22
13.0 Replacement Parts.....................................................................................................................................23
13.1.1 Headstock Assembly – Exploded View ...............................................................................................23
13.1.2 Headstock Assembly – Parts List........................................................................................................24
13.2.1 Drive Belt Assembly – Exploded View ................................................................................................25
13.2.2 Drive Belt Assembly – Parts List .........................................................................................................26
13.3.1 Belt Tension Lever – Exploded View...................................................................................................27
13.3.2 Belt Tension Lever – Parts List ...........................................................................................................27
13.4.1 Change Gears – Exploded View .........................................................................................................28
13.4.2 Change Gears – Parts List ..................................................................................................................28
13.5.1 Electrical – Exploded View ..................................................................................................................29
13.5.2 Electrical – Parts List...........................................................................................................................30
13.6.1 Chuck Guard – Exploded View ...........................................................................................................31
13.6.2 Chuck Guard – Parts List ....................................................................................................................31

6
13.7.1 Gear Box – Exploded View .................................................................................................................32
13.7.2 Gear Box – Parts List ..........................................................................................................................33
13.8.1 Apron I – Exploded View .....................................................................................................................35
13.8.2 Apron I – Parts List..............................................................................................................................36
13.9.1 Apron II – Exploded View ....................................................................................................................37
13.9.2 Apron II – Parts List.............................................................................................................................37
13.10.2 Saddle and Cross Slide – Exploded View .........................................................................................38
13.10.2 Saddle and Cross Slide – Parts List..................................................................................................39
13.11.1 Compound Slide – Exploded View ....................................................................................................40
13.11.2 Compound Slide – Parts List.............................................................................................................41
13.12.1 Tailstock – Exploded View ................................................................................................................42
13.12.2 Tailstock – Parts List .........................................................................................................................43
13.13.1 Steady Rest – Exploded View ...........................................................................................................44
13.13.2 Steady Rest – Parts List....................................................................................................................44
13.14.1 Follow Rest – Exploded View............................................................................................................45
13.14.2 Follow Rest – Parts List.....................................................................................................................45
13.15.1 BD-919 Bed Assembly – Exploded View ..........................................................................................46
13.15.2 BDB-919 Bed Assembly – Parts List.................................................................................................47
13.16.1 BDB-929 Bed Assembly – Exploded View ........................................................................................48
13.16.2 BDB-929 Bed Assembly – Parts List.................................................................................................49
13.17.1 Accessories – Exploded View ...........................................................................................................50
13.17.2 Accessories – Parts List ....................................................................................................................50
13.18.1 BDB-919 Stand #321375 (Optional Accessory) – Exploded View ....................................................51
13.18.2 BDB-919 Stand #321375 (Optional Accessory) – Parts List .............................................................51
13.19.2 BDB-929 Stand #321377 (Optional Accessory) – Exploded View ................................................... 52
13.19.2 BDB-929 Stand #321377 (Optional Accessory) – Parts List ............................................................52
14.0 Wiring diagram for BDB-919,929 Lathes ...................................................................................................53
15.0 Speed and threading charts .......................................................................................................................54
16.0 Warranty and service .................................................................................................................................55

7
3.0 Introduction
This manual is provided by JET covering the safe operation and maintenance procedures for a JET Model BDB-
919/929 Bench Lathe. This manual contains instructions on installation, safety precautions, general operating
procedures, maintenance instructions and parts breakdown. This machine has been designed and constructed
to provide consistent, long-term operation if used in accordance with instructions set forth in this manual. If there
are any questions or comments, please contact either your local supplier or JET. JET can also be reached at our
web site: www.jettools.com.
This manual is not intended to be a training guide for lathe operations, or tool and workpiece selection. Consult
a machinery handbook or shop supervisor for information on proper speed and feed rates for specific materials,
or type of cutter suitable for a particular operation. Whatever accepted methods or materials are used, always
make personal safety a priority.
If there are questions or comments, please contact your local supplier or JET. JET can also be reached at our
web site: www.jettools.com.
Retain this manual for future reference. If the machine transfers ownership, the manual should accompany it.
Read and understand the entire contents of this manual before attempting assembly or
operation! Failure to comply may cause serious injury!
Register your product using the mail-in card provided, or register online: http://www.jettools.com/us/en/service-
and-support/warranty/registration/
4.0 Specifications
Model number BDB-919 BDB-929
Stock number 321378 321379
Motor and Electricals
Motor type TEFC induction
Horsepower 3/4 HP (550W)
Phase single
Voltage 115 V
Cycle 60 Hz
Listed FLA (full load amps) 8.5 A
Motor speed 1720 RPM
Power cord 3 x 1.31 mm²
Power plug installed 15A
Recommended circuit size 115A
Sound emission without load 288 db
Capacities
Swing over bed 8-3/4 in.
Swing over cross slide 5 in.
Distance between centers 18 in. 27-1/2 in.
Steady rest capacity 14 – 1-3/4 in.
Follow rest capacity 1-3/4 in.
Headstock
Hole through spindle 3/4 in.
Spindle Nose 1-1/2 in. x 8 TPI
Taper in spindle MT-3
Spindle bearing type Tapered roller
Number of spindle speeds 6
Range of spindle speeds 130 – 2000 RPM

8
BDB-919 BDB-929
Gearbox
Number of longitudinal feeds 60
Range of longitudinal feeds 0.0006 – 0.037 in.
Number of inch threads 27
Range of inch threads 8 – 56 TPI
Number of metric threads 12
Range of metric threads 0.5 – 3.5 mm
Compound and Carriage
Tool post type Single and 4-way
Maximum tool size 1/2 x 1/2 in.
Maximum compound slide travel 1-7/8 in.
Maximum cross slide travel 4-1/4 in.
Maximum carriage travel 17-1/2 in. 26-1/2 in.
Tailstock
Tailstock spindle travel 1-9/16 in.
Diameter of tailstock spindle 1-1/6 in.
Taper in tailstock spindle MT-2
Main materials
Headstock Cast iron
Bed Cast iron
Apron/Saddle Cast iron
Tailstock Cast iron
Splash guard Steel
Dimensions
Bed width 4-1/2 in.
Overall dimensions (LxWxH) 41 x 22 x 20 in. 51 x 22 x 20 in.
Shipping dimensions (LxWxH) 41 x 22 x 22 in. 51 x 22 x 22 in.
Weights
Net weight (approx.) 250 lbs 287 lbs
Shipping weight (approx.) 293 lbs 344 lbs
1subject to local and national electrical codes.
2The specified values are emission levels and are not necessarily to be seen as safe operating levels. As workplace
conditions vary, this information is intended to allow the user to make a better estimation of the hazards and risks
involved only.
L = length, W = width, H = height, TPI = threads per inch
n/a = not applicable
The specifications in this manual were current at time of publication, but because of our policy of continuous
improvement, JET reserves the right to change specifications at any time and without prior notice, without incurring
obligations.

9
5.0 Unpacking
Open shipping container and check for shipping damage; report any damage immediately to your distributor and
shipping agent. Do not discard any shipping material until the Lathe is assembled and running properly. Compare
the contents of your container with the following parts list to make sure all parts are intact. Missing parts, if any,
should be reported to your distributor. Read the instruction manual thoroughly for assembly, maintenance and
safety instructions.
5.1 Contents of shipping container
Referring to Figure 1:
1 Lathe (not shown)
1 7-1/4” Four-Jaw Independent Chuck (A)
1 Faceplate (B)
1 4” Three-Jaw Universal Chuck (pre-mounted)
1 Four Way Tool Post (pre-mounted)
1 Steady Rest (pre-mounted)
1 Follow Rest (pre-mounted)
1 Operator's Manual (not shown)
1 Product Registration Card (not shown)
2 Chuck Reversing Jaws, Set of 3* (F)
1 MT-2 Center* (H)
1 MT-3 Center* (I)
1 56T Gear (pre-mounted)
1 52T Gear* (J)
1 48T Gear* (K)
1 46T Gear* (L)
1 45T Gear* (M)
1 44T Gear* (N)
1 40T Gear* (O)
1 38T Gear* (P)
2 32T Gear* (Q)
1 30T Gear* (R)
1 28T Gear (pre-mounted)
1 Tension Roller Lever* (S)
1 Handle* (T)
1 Female Chuck Key* (U)
2 Male Chuck Keys* (V)
1 #1 Cross Point Screwdriver* (W)
1 #1 Flat Blade Screwdriver* (X)
1 5pc Hex Wrench Set (Y)*
1 4mm T-Handle Hex Wrench* (not shown)
2 Open End Wrenches – 8/10mm, 12/14mm* (Z)
* parts marked with an asterisk are included in the tool box, stock no. BDB919-TBC
Read and understand the entire contents of this manual before attempting set-up or
operation! Failure to comply may cause serious injury.
CAUTION
The three jaw chuck and the face plate have a set screw on their flanges that secures them to the
threaded spindle. Before removing the three jaw chuck or the faceplate, remove the set screw
completely from the flange. Failure to remove the set screw may cause damage to the threads on
the spindle. When installing either the jaw chuck or the faceplate, tighten the set screw firmly to
prevent the chuck or the faceplate from coming off the spindle during operation.
Figure 1

10
6.0 Setup and preparation
for operation
To avoid twisting the bed, make sure the location to
which the lathe will be moved is absolutely flat and
level. Place a machinist’s level on the bed ways and
check for level side-to-side and front to rear. If stand
mounted, the stand must be fastened to the floor. (An
optional JET stand is available for the lathe BDB-
919, order stock no. 321375)
Remove rust protectant from all surfaces with a soft
rag and kerosene, diesel oil, or a mild solvent. Do not
use gasoline, paint thinner, or lacquer thinner, as
these may damage painted surfaces. After cleaning,
wipe with a clean, dry cloth and cover all machined
surfaces with a light film of machine oil.
Carefully read the grounding instructions on pages 2
and 3. It is recommended that the BDB-919 and
BDB-929 Lathes be connected to a dedicated,
minimum 25 amp circuit with a circuit breaker or time
delay fuse. Local codes take precedence over
recommendations.
7.0 General description
7.1 Lathe bed
The Lathe bed is made of high-grade iron. By
combining high cheeks with strong cross ribs, a bed
of low vibration and rigidity is produced. The main
motor is mounted to the rear of the bed (Figure 2).
7.2 Headstock
The headstock (Figure 3) is cast from high grade, low
vibration cast iron. It is bolted to the bed with four
screws and uses four adjusting screws for alignment.
In the head the large main spindle is mounted on two
precision taper roller bearings. The hollow spindle is
a Morse taper No.3 with a 3/4” bore
A quick change of the belt can be accomplished by
easing the tension on the idler (Figure 4).
To protect the machine against accidental damage,
a clutch is fitted to the reduction pulley at the 130
R.P.M. speed.
Figure 2
Figure 3
Figure 4