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Stepper Motor NEMA^ Sizes

NEMA is "National Electrical Manufacturers Association" and their standard for motor mounts is commonly used in the industry to ensure that replacement parts will fit and be readily available, and that motors from different mfgs will be interchangeable. The NEMA number is related to the diameter of the motor times 10. So a NEMA 23 motor is 2.3 inches around or down the side.

Please note: These figures are put together from multiple sources and may or may not be right. Please let us know if there is an error.
Dimension in Inches (mm) NEMA Motor Mounting Dimensions
Motor Size (DD) ~0.8 ~1.1 ~1.4 ~1.7 ~2.3 ~3.4 ~4.2
a: Bolt Hole Distance (square) 0.630 (16) 0.905 (23)   1.024 (26)   1.220 (31)   1.854 (47.14)   2.744 (69.7)   3.500 (88.9)  
b: Motor Shaft Diameter 0.157 (4) 0.197 (5) 0.197 (5) 0.197 (5) 0.250 (6.35) 0.375 (9.5) 0.625 (16)
c: Motor Shaft Length (max) 0.945 0.810 1.250 1.380
d: Pilot Diameter 0.590 (15) 0.866 (22) 0.866 (22) 0.866 (22) 1.500 (38.1) 2.875 (73) 2.186
e: Pilot Depth (max) 0.059 (1.5) 0.079 (2) 0.079 (2) 0.079 (2) 0.062 (1.6) 0.062 (1.6) 0.062 (1.6)
f: Bolt Hole Circle Diameter 1.725 2.625 3.875 4.950
g: Bolt Hole Size 0.118 (3) 0.157 (4) 0.157 (4) 4-40 UNC 0.195 (5) 0.218 (5.5) 0.281

Thanks to Neil (PICDude) for these excellent pictures!

Thanks Neil (PICdude)!Thanks Neil (PICdude)!

The primary NEMA number specifies the position and size of the mounting face as shown in the table above. The full NEMA standard also describes other features of the motor. The full NEMA description of a stepper motor is written as:

For example: a 3.4" diameter stepper motor with a flange that is 1.6 inches long, has a phase current of 1.2 Amps, class B insulation, 5.3 phase voltage, 200 steps per revolution, and 8 wires is: NEMA 34D016-012B053200F

See also:



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