Jet GHB-1236 Troubleshooting guide

1
Operation and Maintenance Instructions
Geared Head Bench Lathe
Model GHB-1236
JET
427 New Sanford Road
LaVergne, Tennessee 37086 Part No. M-321236
Ph.: 800-274-6848 Edition 2 05/2019
www.jettools.com Copyright © 2017 JET
This .pdf document is bookmarked

1.0 IMPORTANT SAFETY
INSTRUCTIONS
Read and understand the entire owner's
manual before attempting set-up or operation
of this lathe.
1. This machine is designed and intended for use
by properly trained and experienced personnel
only. If you are not familiar with the proper and
safe use of lathes, do not use this machine
until proper training and knowledge have been
obtained.
2. Keep guards in place. Safety guards must be
kept in place and in working order.
3. Remove adjusting keys and wrenches. Before
turning on machine, check to see that any
adjusting wrenches are removed from the tool.
4. Reduce the risk of unintentional starting. Make
sure switch is in the OFF position before
plugging in the tool.
5. Do not force tools. Always use a tool at the
rate for which it was designed.
6. Use the right tool. Do not force a tool or
attachment to do a job for which it was not
designed.
7. Maintain tools with care. Keep tools sharp and
clean for best and safest performance. Follow
instructions for lubrication and changing
accessories.
8. Always disconnect the tool from the power
source before adjusting or servicing.
9. Check for damaged parts. Check for alignment
of moving parts, breakage of parts, mounting,
and any other condition that may affect the
tool’s operation. A guard or any part that is
damaged should be repaired or replaced.
10. Turn power off. Never leave a tool unattended.
Do not leave a tool until it comes to a complete
stop.
11. Keep work area clean. Cluttered areas and
benches invite accidents.
12. Do not use in a dangerous environment. Do
not use power tools in damp or wet locations,
or expose them to rain. Keep work area well
lighted.
13. Keep children and visitors away. All visitors
should be kept a safe distance from the work
area.
14. Make the workshop child proof. Use padlocks,
master switches, and remove starter keys.
15. Wear proper apparel. Loose clothing, gloves,
neckties, rings, bracelets, or other jewelry may
get caught in moving parts. Non-slip footwear
is recommended. Wear protective hair
covering to contain long hair. Do not wear any
type of glove.
16. Always use safety glasses. Every day glasses
only have impact resistant lenses; they are not
safety glasses.
17. Do not overreach. Keep proper footing and
balance at all times.
18. Do not place hands near the chuck while the
machine is operating.
19. Do not perform any set-up work while machine
is operating.
20. Read and understand all warnings posted on
the machine.
21. This manual is intended to familiarize you with
the technical aspects of this lathe. It is not, nor
was it intended to be, a training manual.
22. Do not attempt to adjust or remove tools
during operation.
23. Never stop a rotating chuck or workpiece with
your hands.
24. Choose a low spindle speed when working
unbalanced workpieces, and for threading and
tapping operations.
25. Do not exceed the maximum speed of the
workholding device.
26. Do not exceed the clamping capacity of the
chuck.
27. Workpieces longer than 3 times the chucking
diameter must be supported by the tailstock or
a steady rest.
28. Avoid small chuck diameters with large turning
diameters.
29. Avoid short chucking lengths and small
chucking contact.
30. Turn off the machine and disconnect from
power before cleaning. Use a brush to remove
shavings or debris — do not use your hands.
31. Do not stand on the machine. Serious injury
could occur if the machine tips over.
32. Never leave the machine running unattended.
Turn the power off and do not leave the
machine until moving parts come to a
complete stop.

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33. Remove loose items and unnecessary work
pieces from the area before starting the
machine.
34. Do not operate the lathe in flammable or
explosive environments. Do not use in a damp
environment or expose to rain.
Familiarize yourself with the following safety notices used in this manual:
This means that if precautions are not heeded, it may result in minor injury and/or possible
machine damage.
This means that if precautions are not heeded, it may result in serious, or possibly even fatal,
injury.
2.0 About this manual
This manual is provided by JET, covering the safe operation and maintenance procedures for a JET Model
GHB-1236 Lathe. This manual contains instructions on installation, safety precautions, general operating
procedures, and maintenance instructions. Your machine has been designed and constructed to provide
consistent, long-term operation if used in accordance with the instructions as set forth in this document.
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/
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.
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.

3.0 Table of contents
Section Page
1.0 IMPORTANT SAFETY INSTRUCTIONS ....................................................................................................... 2
2.0 About this manual .......................................................................................................................................... 3
3.0 Table of contents ............................................................................................................................................ 4
4.0 Specifications ................................................................................................................................................. 6
4.1 Dimensions for provided stand ................................................................................................................... 7
5.0 Setup and assembly ....................................................................................................................................... 8
5.1 Shipping contents ....................................................................................................................................... 8
5.2 Uncrating and cleanup ............................................................................................................................... 9
5.3 Chuck preparation (three jaw) .................................................................................................................... 9
5.4 Chuck guard installation ........................................................................................................................... 10
6.0 Lubrication .................................................................................................................................................... 10
7.0 Electrical connections .................................................................................................................................. 11
7.1 GROUNDING INSTRUCTIONS ............................................................................................................... 11
7.2 Extension cords ........................................................................................................................................ 12
8.0 General description ...................................................................................................................................... 12
8.1 Lathe bed .................................................................................................................................................. 12
8.2 Carriage .................................................................................................................................................... 12
8.3 Headstock ................................................................................................................................................. 12
8.4 Quick change tool post ............................................................................................................................. 12
8.5 Apron ........................................................................................................................................................ 13
8.6 Tailstock ................................................................................................................................................... 13
8.7 Leadscrew and feed rod ........................................................................................................................... 13
8.8 Gear box ................................................................................................................................................... 13
8.9 Steady rest ............................................................................................................................................... 13
8.10 Follow rest .............................................................................................................................................. 13
9.0 Controls ........................................................................................................................................................ 13
10.0 Operation ................................................................................................................................................... 15
10.1 Break-in procedure ................................................................................................................................. 15
10.2 Feed and thread selection ...................................................................................................................... 15
10.3 Change gear replacement ...................................................................................................................... 15
10.4 Automatic feed operation and feed changes .......................................................................................... 15
10.5 Powered carriage travel ......................................................................................................................... 16
10.6 Thread cutting ........................................................................................................................................ 16
11.0 Adjustments ............................................................................................................................................... 16
11.1 Saddle adjustment .................................................................................................................................. 16
11.2 Cross slide adjustment ........................................................................................................................... 16
11.3 Compound slide adjustment ................................................................................................................... 16
11.4 Tailstock adjustment ............................................................................................................................... 16
11.5 Half nut gib adjustment ........................................................................................................................... 17
11.6 Headstock alignment .............................................................................................................................. 17
11.7 Removing gap bridge ............................................................................................................................. 17
11.8 Installing gap bridge ............................................................................................................................... 17
12.0 Thread and feed chart ................................................................................................................................ 18
13.0 Replacement parts ..................................................................................................................................... 19
13.1.1 Bed Assembly – Exploded View .......................................................................................................... 19
13.1.2 Bed Assembly – Parts List .................................................................................................................. 19
13.2.1 Headstock Assembly – Exploded View ............................................................................................... 20
13.2.2 Headstock Assembly – Parts List ........................................................................................................ 22
13.3.1 Gearbox Assembly – Exploded View .................................................................................................. 24
13.3.2 Gearbox Assembly – Parts List ........................................................................................................... 26
13.4.1 Apron Assembly – Exploded View ...................................................................................................... 28
13.4.2 Apron Assembly – Parts List ............................................................................................................... 29
13.5.1 Cross Slide Assembly – Exploded View .............................................................................................. 31
13.5.2 Cross Slide Assembly – Parts List ...................................................................................................... 32
13.6.1 Compound Rest Assembly – Exploded View ...................................................................................... 33
13.6.2 Compound Rest Assembly – Parts List ............................................................................................... 34
13.7.1 Tailstock Assembly – Exploded View .................................................................................................. 36
13.7.2 Tailstock Assembly – Parts List ........................................................................................................... 37

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13.8.1 Change Gears – Exploded View ......................................................................................................... 38
13.8.2 Change Gears – Parts List .................................................................................................................. 38
13.9.1 Feed Rod Assembly – Exploded View ................................................................................................ 39
13.9.2 Feed Rod Assembly – Parts List ......................................................................................................... 40
13.10.2 Motor and Change Gear Enclosure – Exploded View ....................................................................... 41
13.10.2 Motor and Change Gear Enclosure – Parts List ................................................................................ 42
13.11.1 Stand/Brake/Coolant Pump – Exploded View ................................................................................... 43
13.11.2 Stand/Brake/Coolant Pump – Parts List ............................................................................................ 45
13.12.1 Electrical Box Assembly – Exploded View ........................................................................................ 46
13.12.2 Electrical Box Assembly – Parts List ................................................................................................. 47
13.13.1 Steady Rest and Follow Rest – Parts List ......................................................................................... 48
13.13.2 Steady Rest and Follow Rest – Parts List ......................................................................................... 49
13.14.1 Chuck and Leadscrew Guards – Exploded View .............................................................................. 50
13.14.2 Chuck and Leadscrew Guards – Parts List ....................................................................................... 50
13.15.1 Accessories – Exploded View ........................................................................................................... 51
13.15.2 Accessories – Parts List .................................................................................................................... 52
14.0 Wiring Diagram for GHB-1236 ................................................................................................................... 53
15.0 Warranty and service ................................................................................................................................. 54

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4.0 Specifications
Table 1
Model number GHB-1236
Stock number 321236
Motor and Electricals
Motor type TEFC induction
Horsepower 2 HP (1.5 kW)
Phase single
Voltage 230V only
Cycle 60 Hz
Listed FLA (full load amps) 8.5 A
Start capacitor 150F 250V
Run capacitor 20F 450V
Motor speed 1720 RPM
Power cord 16AWG, 3 x 1.31 mm2
Power plug installed n/a
Recommended circuit size 1 15 A
Sound emission without load 2 88 dB
Capacities
Swing over bed 13 in. (330 mm)
Swing over cross slide 7-1/2 in. (190.5 mm)
Distance between centers 33 in. (838 mm)
Swing through gap 18 in. (457 mm)
Length of gap 8-3/4 in. (222.25 mm)
Steady rest capacity 5/16 – 2-15/16 in. (8 – 74.6 mm)
Follow rest capacity 2-3/16 in. (55.6 mm)
Headstock
Hole through spindle 1-9/16 in. (39.7 mm)
Spindle nose D1-4
Taper in spindle nose MT5
Spindle taper adaptor MT3
Spindle bearing type Taper roller bearing
Number of spindle speeds 9
Range of spindle speeds 75-1400 RPM
Leadscrew 7/8 in. x 8 TPI
Feed rod diameter 3/4 in. (19 mm)
Gearbox
Number of longitudinal and cross feed rates 48/36
Range of longitudinal feeds 0.0019 – 0.0472 in./rev
Range of cross feeds 0.0014 – 0.0116 in./rev
Number of inch threads 36
Range of inch threads 4 – 60 TPI
Number of metric threads 32
Range of metric threads 0.4 – 7 mm
Compound and carriage
Tool post type Quick change
Maximum tool size 5/8 x 5/8 in.
Maximum compound slide travel 3 in. (76.2 mm)
Maximum cross slide travel 5-1/2 in. (140 mm)
Maximum carriage travel 27-3/8 in. (695.3 mm)

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Tailstock
Tailstock spindle travel 3-1/2 in. (89 mm)
Diameter of tailstock spindle 1-1/4 in. (31.8 mm)
Taper in tailstock spindle MT3
Main materials
Headstock Cast iron
Bed Cast iron
Apron/Saddle Cast iron
Tailstock Cast iron
Splash guard Steel
Stand Steel
Dimensions
Bed width 7-1/8 in. (181 mm)
Overall dimensions, L x W x H 66-3/16 x 29-1/2 x 57-1/2 in. (1681 x 749.3 x 1460.5 mm)
Shipping dimensions, L x W x H 66-1/2 x 29-9/16 x 57-1/8 in. (1690 x 750 x 1451 mm)
Weights
Net weight, approx. 1210 lb. (548.8 kg)
Shipping weight, approx. 1430 lb. (648.6 kg)
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.
4.1 Dimensions for provided stand
Figure 4-1: stand dimensions

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5.0 Setup and assembly
5.1 Shipping contents
See Figure 5-1.
1 Lathe
1 Steady Rest (mounted on lathe)
1 Follow Rest (mounted on lathe)
1 6" Three Jaw Chuck (mounted on lathe)
1 8" Four Jaw Chuck (strapped to container)
1 10" Face Plate (strapped to container)
1 Tool Box (strapped to container)
1 Chip Tray
1 Splash Guard
Tool Box contents:
3 Open End Wrenches (10/12, 14/17, 17/19mm)
1 Oil Gun
1 Hex Key Set (2, 3, 4, 5, 6mm)
1 22T Gear
1 26T Gear
1 38T Gear
1 44T Gear
1 52T Gear
2 MT-3 Dead Centers
1 MT-3 Live Center
1 MT-3 to MT-5 Center Sleeve
1 Cross Point Screwdriver
1 Flat Head Screwdriver
1 Quick Change Tool Holders
(250-202, 250-204, 250, 207, 250-210)
1 Key for 3-Jaw Chuck
1 Key for 4-Jaw Chuck
1 Key for Cam Locks
1 Set of Reverse Jaws for 3-Jaw Chuck
1 Handle for Cross Slide Handwheel
1 Handle for Apron Handwheel
2 V-Belts (A-813)
6 Leveling Pads (with M14x50 Bolts & Washers)
1 Operation and Maintenance Instructions
1 Packing List
1 Test Record
1 Product Registration Card
Figure 5-1

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5.2 Uncrating and cleanup
Machine is heavy. Use an
appropriate lifting device and use extreme
caution when moving the machine to its final
location. Failure to comply may cause serious
injury.
1. Finish removing wooden crate from around
lathe.
2. Unbolt lathe from shipping crate bottom.
3. Choose a location for the lathe that is dry, has
good lighting, and has enough room to be able
to service the lathe on all four sides.
4. Move carriage and tailstock to the tailstock end
of the bed.
5. Place two steel rods or pipes of sufficient
strength into four holes (A, Figure 5-2) of lathe
stand. Sling the lathe with properly rated
straps. Do not lift by spindle. With adequate
lifting equipment, slowly raise lathe off
shipping crate bottom. Make sure lathe is
balanced before moving to sturdy bench or
optional stand.
Figure 5-2
6. To avoid twisting the bed, the lathe's location
must be absolutely flat and level. Bolt lathe to
stand (if used). If using a bench, through-bolt
for best performance.
7. Clean all rust protected surfaces using a mild
commercial solvent, kerosene or diesel fuel.
Do not use paint thinner, gasoline, or lacquer
thinner, as these will damage painted
surfaces. Cover all cleaned surfaces with a
light film of Mobil DTE Oil Heavy Medium or
equivalent.
8. Remove end gear cover. Clean all
components of end gear assembly and coat all
gears with a heavy, non-slinging grease.
9. Using a machinist’s precision level on the
bedways, check to make sure lathe is level
side to side and front to back. If necessary,
loosen mounting bolts, shim, and retighten
mounting bolts. The lathe must be level to be
accurate.
5.3 Chuck preparation (three jaw)
Read and understand all
directions for chuck preparation. Failure to
comply may cause serious injury and/or
damage to the lathe.
Note: Before removing chuck from spindle, place
a way board across bedways under the chuck.
1. Support the chuck while turning three
camlocks 1/4 turn counter-clockwise with the
chuck key enclosed in the toolbox. Figure 5-3
shows the cam in the secure position. Line up
the two marks (A, Figure 5-3) for removal.
Figure 5-3
2. Carefully remove chuck from spindle and place
on an adequate work surface.
3. Inspect the camlock studs. Make sure they
have not become cracked or broken during
transit. Clean all parts thoroughly with solvent.
Also clean spindle and camlocks.
4. Cover all chuck jaws and scroll inside the
chuck with Mobilith AW2. Cover spindle, cam
locks, and chuck body with a light film of Mobil
DTE Oil Heavy Medium.
5. Lift chuck up to spindle nose and press onto
spindle. Tighten in place by turning cam locks
1/4 turn clockwise. The index mark (A, Figure
5-3) on the camlock should be between the
two indicator arrows (B, Figure 5-3). If the
index mark is not between the two arrows,
remove chuck and adjust the camlock studs by
either turning out one full turn (if cams will not
engage) or turning in one full turn (if cams turn
beyond indicator marks).
6. Install chuck and tighten in place.
ATTENTION: Only when the incised line on chuck
lines up with that on the spindle, can the chuck be
mounted.

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5.4 Chuck guard installation
Install chuck guard to headstock, if it is not already
mounted. (See parts breakdown if clarification is
needed for assembly.)
6.0 Lubrication
Lathe must be serviced at all
lubrication points and all reservoirs filled to
operating level before lathe is placed into
service. Failure to comply may cause serious
damage to lathe.
1. Headstock – Oil must be up to indicator mark
in oil sight glass (A, Figure 6-1). Top off with
Mobil DTE Oil Heavy Medium. Fill by pulling
plug located on top of headstock cover
beneath rubber mat. Drain oil by removing
drain plug (C, Figure 6-2) and refill after first
month of operation. Clean out any metal
shavings. Then, change oil in headstock
annually.
2. External Gears – Coat all gears with a heavy,
non-slinging grease, see Figure 6-2. Do not
get grease on pulleys or belts.
3. Gear Shaft – Remove set screw (F, Figure 8-
2) and oil with a couple drops of Mobil DTE
Oil Heavy Medium once weekly.
4. Gearbox – Oil must be up to indicator mark in
oil sight glass (B, Figure 6-1). Top off with
Mobil DTE Oil Heavy Medium. Fill by
removing plug (D, Figure 6-2). Drain oil by
removing drain plug (E, Figure 6-2) and refill
after first month of operation. Then, change oil
in gearbox annually.
5. Apron – Oil must be up to indicator mark in oil
sight glass (A, Figure 6-3). Top off with Mobil
DTE Oil Heavy Medium. Fill by removing oil
plug (B, Figure 6-3). After the first three
months of operation, drain oil completely (drain
is on bottom of apron) and refill with Mobil
DTE Oil Heavy Medium, or equivalent to the
indicator line. Then, change oil annually.
6. Carriage – Lubricate two ball oilers on top of
carriage once daily with Mobil DTE Oil Heavy
Medium.
Figure 6-1
Figure 6-2
Figure 6-3