- Add to Favorites
  
  Sign-in or create a free RegalRexnord.com Account to save this page to your favorites list for easy access.
  
  Login >
  
  Added To Favorites
  
  This page has been added to your favorites list.
  
  View My Favorites >
  
  Removed from Favorites
  
  This page has been removed from your favorites list. To re-add, click the star icon again.
  
  View My Favorites >
  
  Favorites List Full
  
  Your favorites list is full. Please remove other favorite(s) to add this page.
  
  View My Favorites >
  
  Add to Favorites
  
  Save this page to your favorites list for easy access.
  
  View My Favorites >

Electric Motor Shaft Types & Frame Sizes: What You Need to Know

Motor Shaft Types And NEMA® Frames

Electric motors are designed with their operating environments in mind. Manufacturers build motors for specific purposes. Motor construction often reflects intended application. This includes everything from the motor’s shaft size to its frame type.

Understanding these design elements can help you choose the right motor. It can also guide how you on how to install and position the motor in your space.

Motors must meet the demands of OEMs, distributors, and aftermarket customers. Manufacturers in the U.S. created a nonprofit trade group to standardize production. The National Electric Manufacturers Association (NEMA) creates guidelines for motor production. These guidelines promote consistency and compatibility.

For electric motors, NEMA standards define key specifications. Specifications include factors like:

Frame sizes,
Mounting dimensions,
Shaft diameters,
Horsepower ratings,
Service factors, and
Temperature rise limits.

NEMA standards make the motor selection process easier for customers. With them, manufacturers can produce motors that are easier to compare, replace, or integrate—regardless of brand.
Understanding NEMA standards can help users simplify motor selection. This is especially true with issues like frame and shaft size. Choosing the right motor will ensure it fits in your system and performs as expected in your specific application.

NEMA Frame Dimensions, Explained

A motor’s frame number states that motor's physical size. This is typically the mounting, steel shaft heights, and other factors. Factors like electrical characteristics (including horsepower) do not factor into frame size. When it comes to NEMA frame size, these numbers refer to mounting only. They have no direct bearing on the motor body diameter. As a frame number increases, generally so do the physical size of the motor and horsepower. There are many motors of the same horsepower built in different frames.

By understanding the relationship between the two/three digit NEMA frame dimensions and shaft type/size, you can clearly identify the motor’s enclosure orientation.

In NEMA standards, two-digit frame numbers are fractional frames even though 1 HP or larger motors may be built in them. Three-digit frame numbers are by definition integral frames. The third numeral indicates the distance between the mounting holes parallel to the base. It has no significance in a footless motor.

Examples of these distances can be found with frame numbers 48, 56, 145, and 215. The frame number relates to the “D” dimension (distance from the center of the shaft to the center bottom of the mount). In the two-digit 56 frame, below, the “D” dimension is 3 1/2”.

56 Frame → 56
D = 56 ÷ 16
D = 3 ½”

For the “D” dimension of a three-digit frame number, consider only the first two digits. For example, in the frame number 145, the first two digits divided by the constant 4 is equal to the “D” dimension

145 Frame → 145 → 14
D = 14 ÷ 4
D = 3 ½”

Similarly, the “D” dimension of a 213 frame motor is 5 1/4”.
213 Frame → 213 → 23
D = 12 ÷ 4
D = 5 ¼”

NEMA Frame Suffixes

C Frame - NEMA C face mounting (specify with or without rigid base)

D Frame - NEMA D flange mounting (specify with or without rigid base)

H Frame - Indicates a frame with a rigid base having an F dimension larger than that of the same frame without the suffix H. For example, combination 56H base motors have mounting holes for NEMA 56 and NEMA 143-5T, and a standard NEMA 56 shaft

J Frame - NEMA C face, threaded shaft pump motor

JM Frame - Close-coupled pump motor with specific dimensions and bearings

JP Frame - Close-coupled pump motor with specific dimensions and bearings

M Frame - 6 3/4” flange (oil burner)

N Frame - 7 1/4” flange (oil burner)

T, TS Frames - Integral horsepower NEMA standard shaft dimensions if no additional letters follow the “T” or “TS”.

TS Frame - Motor with NEMA standard “short shaft” for belt-driven loads.

Y Frame - Non-NEMA standard mount; a drawing is required to be sure of dimensions. This can indicate a special base, face, or flange.

Z Frame - Non-NEMA standard shaft; a drawing is required to be sure of dimensions.

Frame Prefixes

Letters or numbers appearing in front of the NEMA frame number are manufacturer designated prefixes. They hold no NEMA frame significance and vary from one manufacturer to another. For example, the letter in front of the LEESON® frame number, L56, indicates the overall length of the motor.

NEMA T Frame Dimensions

Nema
Series

N-W

AA
Size

BA*

XO/T^

Tap

Key Size
sq.

2 5/8

1 3/4

27/32

9/32
Slot

1 1/4

5 1/16

4 7/8

3/8

1 1/8

3/8

4.5

1 5/16

3 3/4

2 1/6

1/8

4 7/8

1 5/8

5 1/8

1/4-20(4)

3/64 Flat

2.125

1 3/8

11/32
Slot

1 5/8

5 7/8

5 5/8

1/2

1 1/2

1/2

4 7/8

1 11/16

3 3/4

2 1/2

1/8

2 1/4

5 7/8

1/4-20(4)

3/64 Flat

56
56H

3 1/2

2 7/16

1 1/2
2 1/2

11/32
Slot

6 7/8

6 5/8

5/8

1 7/8

1/2

5 3/8

2 1/16

5 7/8

4 1/2

2 3/4

1/8

6 1/2

2 1/4

7 1/4

3/8-16(4)

3/16

143T
145T

3 1/2

2 3/4

2
2 1/2

11/32

2 3/8

6 7/8

6 5/8

7/8

2 1/4

3/4

6 3/8

2 1/8

5 7/8

4 1/2

2 1/4*

1/8

6 1/2

2 1/4

7 1/4

3/8-16(4)

3/16

182T
184T

4 1/2

3 3/4

2 1/4
2 3/4

13/32

−

8 3/4

8 1/2

1 1/8

2 3/4

3/4

6 3/8

2 5/8

7 1/4

8 1/2

2 3/4*

1/4

8 7/8

2 1/2

9 1/8

1/2-13(4)

1/4

213T
215T

5 1/4

4 1/4

2 3/4
3 1/2

13/32

−

10 5/8

9 3/4

1 3/8

3 3/8

3/4

8 3/8

3 1/8

7 1/4

8 1/2

3 1/2*

1/4

1 3/4

10 3/4

1/2-13(4)

5/16

254T
256T

6 1/4

4 1/8
5

17/32

−

1 5/8

1 1/4

10 1/2

3 3/4

7 1/4

8 1/2

4 1/2*

1/4

2 1/4

1/2-13(4)

3/8

284T
284TS

5 1/2

4 3/4

17/32

−

14 1/2

13 3/8

1 7/8
1 5/8

4 5/8
3 1/4

1 1/2

11 7/8

4 3/8
3

10 1/2

4 3/4

1/4

11 1/4

2 1/4

14 1/2

1/2-13(4)

1/2
3/8

286T
286TS

5 1/2

−

1 7/8
1 5/8

4 5/8
3 1/4

4 3/8
3

1/2
3/8

324T
324TS

6 1/4

5 1/4

21/32

−

16 1/8

15 7/8

2 1/8
1 7/8

5 1/4
3 3/4

5
3 1/2

12 1/2

5 1/4

1/4

2 5/8

16 1/8

5/8-11(4)

5/8
1/2

326T
326TS

2 1/8
1 7/8

5 1/4
3 3/4

5
3 1/2

5/8
1/2

364T
364TS

5 5/8

21/32

−

18 3/8

17 7/8

2 3/8
1 7/8

5 7/8
3 3/4

5 5/8
3 1/2

12 1/2

5 7/8

1/4

2 5/8

18 3/8

5/8-11(8)

5/8
1/2

365T
365TS

6 1/8

2 3/8
1 7/8

5 7/8
3 3/4

5 5/8
3 1/2

5/8
1/2

404T
404TS

6 1/8

13/16

−

19 5/8

2 7/8
2 1/8

7 1/4
4 1/4

7
4

12 1/2

6 5/8

1/4

2 5/8

5/8-11(8)

3/4
1/2

405T
405TS

6 7/8

2 7/8
2 1/8

7 1/4
4 1/4

7
4

3/4
1/2

444T
444TS

7 1/4
7 1/4

13/16

−

21 3/4
21 3/4

21 3/8
21 3/8

3 3/8
2 3/8

8 1/2
4 3/4

8 1/4
4 1/2

7 1/2

1/4

3
3

21 1/2
21 1/2

5/8-11(8)

7/8
5/8

445T
445TS

8 1/4
8 1/4

21 3/4
21 3/4

21 3/8
21 3/8

3 3/8
2 3/8

8 1/2
4 3/4

8 1/4
4 1/2

3
3

21 1/2
21 1/2

7/8
5/8

447T
447TS

10
10

23
23

22 3/4
22 3/4

3 3/8
2 3/8

8 1/2
4 3/4

8 1/4
4 1/2

3 1/4
3 1/4

24
24

7/8
5/8

449T
449TS

12 1/2
12 1/2

23
23

23 3/8
23 3/8

3 3/8
2 3/8

8 1/2
4 3/4

8 1/4
4 1/2

3 1/4
3 1/4

24
24

7/8
5/8

For more information on motor shaft types and their relationship to NEMA frames, contact our commercial motor experts below.

Talk To Our Sales Team

We're here to help. Our team of experts is ready to help energy-efficiently power your business.

Electric Motor Shaft Types & Frame Sizes: What You Need to Know

Motor Shaft Types And NEMA® Frames

NEMA Frame Dimensions, Explained

NEMA Frame Suffixes

Frame Prefixes

NEMA T Frame Dimensions

Talk To Our Sales Team

About

Contact