Last updated on Tuesday, March 02, 2021 07:35:52 PM Mountain US Time Zone
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 & Z1 Axes Scales
9x20 Lathe 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
AXA 9"-12" swing
BXA 10"-15" swing
CXA 13"-18" swing
AXA, BXA, CXA sizes, available.
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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||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.
An 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. 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.
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.