BD-920N 9x20 Lathe
Last updated on Saturday, October 19, 2019 11:58:21 AM Mountain US Time Zone
Original Design, Jet BD-920N, Specifications, Belts, Gears, Gear Ratios, Lathe Machine Mounts
Original 8"x17" (195mm x 450mm) Emco-Maier Compact 8 (Austria), father of the current breed of 9x20 lathes.
9x20 Lathe DRO X
Tachometer & SFM
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.
Click on linked thumbnails
Click on linked thumbnails
|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|
|Motor Cogged Belt||170 XL 050|
|Pulley V-Belt||5M710 Polyflex|
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. A 85 teeth 170XL050 timing belt is on the motor.
The Gates 5M710 Polyflex
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"
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.
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.