Jet BD-920N 9x20 Lathe Specifications & Views
Last updated on Sunday, March 19, 2017 09:35:23 AM Eastern US Time Zone

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

9x20 Lathe DRO X & Z1 Axes Scales. Tailstock DRO  9x20 Lathe Tachometer & SFM    BD-920N manual

Original Design
Emco9x18.jpg (38934 bytes)
Original 8"x17" (195mm x 450mm) Emco-Maier Compact 8 (Austria), father of the current breed of 9x20 lathes.

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.

More books on machining.

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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-lbs.
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.
R
educe 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. A 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 3 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.

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

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