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RIGID CONDUIT AND KNOCKOUT SIZES

Conduit is used to protect and support electrical wires.

Both rigid conduit and intermediate metallic conduit are threaded and accept couplings, nuts, and bushings et cetera directly.

ALL SIZES ARE INCHES

INSIDE DIAMETER

(ID)

OUTSIDE DIAMETER (OD)

KNOCKOUT SIZE

TRADE SIZE

THREADS PER INCH

NOMINAL (1)

NOMINAL

MAXIMUM (2)

NOMINAL (3)

1/4

18

0.364

0.540

N/A

0.575

3/8

18

0.493

0.675

N/A

0.718

1/2

14

0.634

0.840

0.855

0.875

3/4

14

0.836

1.050

1.066

1.109

1

11-1/2

1.063

1.315

1.331

1.375

1-1/4

11-1/2

1.394

1.660

1.676

1.734

1-1/2

11-1/2

1.624

1.900

1.916

1.984

2

11-1/2

2.083

2.375

2.399

2.469

2-1/2

8

2.489

2.875

2.904

2.969

3

8

3.090

3.500

3.535

3.594

3-1/2

8

3.570

4.000

4.040

4.123

4

8

4.050

4.500

4.545

4.641

4-1/2

8

4.506

5.000

5.050

5.109

5

8

5.073

5.563

5.619

5.719

6

8

6.093

6.625

6.691

6.813

(1) U.L. Table NAE.3.

(2) Maximum Outside Diameter Per ANSI C80.1-1977.

(3) Dimensions for trade sizes of 1/4 through 1-1/4 are from Table 20.2 of ANSI/UL 514-1978.
Sizes 1/ 2 " thru 6" per proposed revision to NEMA Engineering Bulletin No. 71, Aug. 1976.



PLASTIC CONDUIT BUSHING SIZES

ALL SIZES ARE INCHES

TRADE SIZE

DIMENSION A

DIMENSION B

1/2

1.050

0.365

3/4

1.280

0.390

1

1.632

0.490

1-1/4

1.986

0.535

1-1/2

2.160

0.550

2

2.680

0.600

2-1/2

3.150

0.635

3

3.800

0.725

3-1/2

4.275

0.725

4

4.775

0.750

5

6.350

0.975

6

7.475

0.975

INTERMEDIATE METALLIC CONDUIT  (IMC)

ALL SIZES ARE INCHES

INSIDE DIAMETER (ID)

OUTSIDE DIAMETER (OD)

TRADE SIZE

THREADS PER INCH

NOMINAL

NOMINAL

MAXIMUM

1/2

14

0.675

0.815

0.820

3/4

14

0.879

1.029

1.034

1

11-1/2

1.120

1.290

1.295

1-1/4

11-1/2

1.468

1.638

1.645

1-1/2

11-1/2

1.703

1.883

1.890

2

11-1/2

2.170

2.360

2.367

2-1/2

8

2.597

2.857

2.867

3

8

3.216

3.476

3.486

3-1/2

8

3.711

3.971

3.981

4

8

4.206

4.466

4.476

U.L. Proposed Dimensions for Intermediate Metallic Conduit - Type I.

IMC Threads and Knockout Sizes are the same as Rigid Metal Conduit.

Standard rigid threaded conduit fittings can be used with I.M.C.



Electrical metallic tubing is not threaded, and must be connected to junction boxes and the like with conduit connectors that secure to the tubing by means of a set screw or collet and nut; then the connectors have integrated shoulders and threads that secure to the box with a nut.

ELECTRICAL METALLIC TUBING (EMT) IT  (IMC)

ALL SIZES ARE INCHES

INSIDE DIAMETER (ID)

WALL THICKNESS

OUTSIDE DIAMETER (OD)

TRADE SIZE

NOMINAL

NOMINAL

NOMINAL

TOLERANCE

3/8

0.493

0.042

0.577

+/- .005

1/2

0.622

0.042

0.706

+/- .005

3/4

0.824

0.049

0.922

+/- .005

1

1.049

0.057

1.163

+/- .005

1-1/4

1.380

0.065

1.510

+/- .005

1-1/2

1.610

0.065

1.740

+/- .005

2

2.067

0.065

2.197

+/- .005

* 2-1/2

2.731

0.072

* 2.875

+/- .010

* 3

3.356

0.072

* 3..500

+/- .015

* 3-1/2

3.834

0.083

* 4.000

+/- .020

* 4

4.334

0.083

* 4.500

+/- .020

* These sizes of EMT have the same nominal outside diameter as the corresponding size rigid conduit. EMT is sometimes called "thin-wall conduit".