Jet
BD-920N
9x20 Lathe
Specifications &
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Last updated on
Tuesday, March 02, 2021 07:35:52 PM
Mountain US Time Zone
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Original Design,
Jet BD-920N,
Specifications,
Belts,
Gears,
Gear Ratios,
Lathe Machine Mounts
Original Design
Original 8"x17" (195mm x 450mm)
Emco-Maier Compact 8
(Austria),
father of the current breed of 9x20
lathes.
9x20 Lathe DRO
X
&
Z1 Axes
Scales
Tailstock DRO
9x20 Lathe
Tachometer & SFM
BD-920N manual
Jet BD-920N
DRO-equipped
Jet
9x20 belt drive metal
lathe Model BD-920N &
S-920N stand manual.
The lathe is at the upper limits of weight & size that
I could safely move down a
hill & into my lower-level walkout.
Click on linked thumbnails
#ad
AXA 9"-12" swing
BXA 10"-15" swing
CXA 13"-18" swing
AXA, BXA, CXA sizes, available.
Click on linked thumbnails
#ad
Swing Over Bed | 9" |
Swing Over Cross Slide | 5-5/16" |
Distance Between Centers | 20" |
Hole Through Spindle | 25/32" (0.78125") |
Spindle Mount | 1-1/2 x 8 TPI |
Spindle Taper With Sleeve | MT3 |
Number of Spindle Speeds | 6 |
Range of Spindle Speeds | 130 - 2,000 RPM |
Number of Longitudinal Feeds | 27 |
Range of Longitudinal Feeds | 0.005 - 0.011"/rev |
Number of Inch Threads | 27 |
Range of Inch Threads | 8 - 56 TPI |
Number of Metric Threads | 11 |
Range of Metric Threads | 0.05 - 3 mm |
Max Tool Size | 1/2" x 1/2" |
Max Compound Slide Travel | 1-7/8" |
Max Cross Slide Travel | 5" |
Max Carriage Travel | 16" |
Tailstock Spindle Travel | 1-9/16" |
Taper in Tailstock Spindle | MT2 |
Steady Rest Capacity | 1/4" x 1-7/8" |
Follow Rest Capacity | 1/4" x 1-1/8" |
Width of Bed | 4-1/2" |
Overall Dimensions with Stand | 37-1/2" L x 20" W x 45" H |
Main Motor | 3/4 HP, 1 Ph 115V only |
Weight | 235 lb |
Stock Number | 321373 |
Motor Cogged Belt | 170 XL 050 |
Pulley V-Belt | 5M710 Polyflex |
Belts
Jet BD-920N Belt Lathe Pulley Ratios
See the
variable-speed DC
motor upgrade.
Reduce
high
idler
belt tension & belt breakage by
installing
an S-link on the spring.
Using the clutch, slip the Gates
5M710 belt (USA) for heavy and/or high RPM loads.
An 85 teeth 170XL050 timing
belt is on the motor.
The Gates 5M710 Polyflex
V-belt
is metric.
5M denotes (a Metric) 5mm top width (3/16"). 710 denotes 710mm
(27.95") outside length.
Cogged timing belts are identified by
three parameters
& are marked as follows. E.g., 170 XL 050
The first number is the belt length in inches. 170 = 17.0"
The letters denote the pitch or the peak to peak tooth spacing. XL = 1/5"
The last number is the belt width in inches. 050 =
1/2"
Click on linked thumbnails #ad
Aluminum safety shear pin at the gearbox
output shaft connection to the lead
screw.
Additional
OEM safety features: pulley slip-clutch
(lowest speed),
thin V-belt drive, & plastic lead screw gear.
The
9x20 variable speed DC
motor upgrade
eliminated the problematic slip-clutch & the weak V-belt.
A metal gear can be substituted for the plastic
version but gearbox noise
will substantially increase.
Gears
Gear
Ratios
Gear ratios for feed rates. See
Jet feed gears.
Other
9x20 lathes have additional gear
sizes that
are
interchangeable with the Jet
BD-920N. Gear ratio charts
differ among the machines (Jet vs.
Enco).
Bought additional gear sizes (120T, 127T) to have more ratios.
Lathe Machine Mounts
The
97 lb
OEM lathe stand
is low in height to accommodate the
installation of machine mounts
which can easily
add 1-1/2 to 2-inches to the lathe's overall
height. Each mount has a steel cup with a rubber vibration absorber &
an adjustment
screw. The six holes in the stand are threaded (3/8-16 for a Jet) but I drilled them out
to 9.5 mm for
a tight fit to the machine mount
M10-1.5 adjustment screws. There are four mounts under the spindle & motor
since
that is where most of the weight is located; six mounts total. They allow easy leveling of
the machine.
Check the front-to-back
leveling on both the left & right sides of the
bed to insure that it is not twisted.