BD-920N 9x20 Lathe
Last updated on Sunday, December 06, 2015 09:02:12 AM Eastern US Time Zone
Original Design, Jet BD-920N, Specifications, Belts, Gears, Gear Ratios, Lathe Machine Mounts
9x20 Lathe DRO X & Z1 axes Scales. 9x20 Lathe Tachometer & SFM BD-920N manual.
Original 8"x17" (195mm x 450mm) Emco-Maier Compact 8 (Austria), father of the current breed of 9x20 lathes.
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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|Swing Over Bed||9"|
|Swing Over Cross Slide||5-5/16"|
|Distance Between Centers||20"|
|Hole Through Spindle||25/32" (0.78125")|
|Spindle Mount||1½ 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||½" x ½"|
|Max Compound Slide Travel||1⅞"|
|Max Cross Slide Travel||5"|
|Max Carriage Travel||16"|
|Tailstock Spindle Travel||1-9/16"|
|Taper in Tailstock Spindle||MT2|
|Steady Rest Capacity||¼" x 1⅞"|
|Follow Rest Capacity||¼" x 1⅛"|
|Width of Bed||4½"|
|Overall Dimensions with Stand||37½" L x 20" W x 45" H|
|Main Motor||¾ HP, 1 Ph 115V only|
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. The 85 teeth 170XL050 timing belt on the motor is from Polybelt.
Timing belts are identified by 3 parameters & are marked as follows - 170 XL 050
Where: The first number is the belt length in inches (170 = 17.0").
The letters denote the pitch; the peak to peak tooth spacing (XL = 1/5").
The last number is the belt width in inches (050 = ½").
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 1½ 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 (⅜-16 for a Jet) but I drilled them out to 9.5 mm for
a tight fit to the Enco 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.