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.
RIGID CONDUIT AND KNOCKOUT SIZES
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
.364
.540
-
.575
3/8
18
.493
.675
-
.718
1/2
14
.632
.840
.855
.875
3/4
14
.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
.365
3/4
1.280
.390
1
1.632
.490
1-1/4
1.986
.535
1-1/2
2.160
.550
2
2.680
.600
2-1/2
3.150
.635
3
3.800
.725
3-1/2
4.275
.725
4
4.775
.750
5
6.350
.975
6
7.475
.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
.675
.815
.820
3/4
14
.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)
ALL SIZES ARE INCHES
INSIDE DIAMETER
(ID)
WALL
THICKNESS
OUTSIDE DIAMETER
(OD)
TRADE
SIZE
NOMINAL
NOMINAL
NOMINAL
TOLERANCE
3/8
.493
.042
.577
+/- .005
1/2
.622
.042
.706
+/-.005
3/4
.824
.049
.922
+/-.005
1
1.049
.057
1.163
+/-.005
1-1/4
1.380
.065
1.510
+/-.005
1-1/2
1.610
.065
1.740
+/-.005
2
2.067
.065
2.197
+/-.005
* 2-1/2
2.731
.072
* 2.875
+/-.010
* 3
3.356
.072
* 3.500
+/-.015
* 3-1/2
3.834
.083
* 4.000
+/-.020
* 4
4.334
.083
* 4.500
+/-.020
*
These sizes of EMT have the same nominal outside
diameter as the corresponding size rigid conduit.
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