JET BD-920N LATHE SPECIFICATIONS
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"

 

 

 

 

 

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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.

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

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Original Design, Jet BD-920N, Specifications,
Belts, Gears, Gear Ratios, Lathe Machine Mounts