THREAD types COMPARISON for CAble Glands

NPT vs
metric vs
PG
ANGLE
GENDER
Taper Angle

Male Female Flank

External Internal Thread
Thread Thread Angle

DESIGN
HANDEDNESS
Parallel

Basics of
Thread Tapered

Right-hand Left-hand

CREST/ROOT
PITCH/TPI
Crest
Pitch

Major diameter

Pitch diameter
1”
Minor diameter
DIAMETER
Threads per Inch

Root
Depth Pitch

Minor Major
diameter diameter

Pitch diameter

National Pipe Tapered

NPT Threads
”- NPT
Nominal
Pipe Size
TPI

A B C
Thread size major diameter Pitch TPI
in inches [mm] in inches [mm] [Thread per inch]
1/16”-27 NPT 0.313 [7.938] 0.037 [0.947] 27

1/8”-27 NPT 0.405 [10.287] 0.037 [0.947] 27

1/4”-18 NPT 0.54 [13.716] 0.056 [1.41] 18

3/8”-18 NPT 0.675 [17.145] 0.056 [1.41] 18

1/2”-14 NPT 0.84 [21.336] 0.071 [1.814] 14

3/4”-14 NPT 1.05 [26.67] 0.071 [1.814] 14

1”-11 1⁄2 NPT 1.315 [33.401] 0.087 [2.208] 11 1⁄2

1.25”-11 1⁄2 NPT 1.66 [42.164] 0.087 [2.208] 11 1⁄2

1.5”-11 1⁄2 NPT 1.9 [48.26] 0.087 [2.208] 11 1⁄2

2”-11 1⁄2 NPT 2.375 [60.325] 0.087 [2.208] 11 1⁄2

C
B
60°
- Taper rate for all NPT threads is 1/16
- The flank angle is 60°
- The taper on NPT threads allows them
to form a seal when torqued as the A
flanks of the threads compress against
each other, as opposed to straight
thread fittings 1° 47’

International Organization for Standardization (ISO)

Metric Threads
M x Major
Diameter Pitch

A B C
fine Thread size major diameter Pitch Through Hole
in inches [mm] in inches [mm] in inches [mm]

M6 x 1.0 0.24 [6] 0.04 [1.0] 0.251 [6.4]

M8 x 1.25 0.31 [8] 0.05 [1.25] 0.33 [8.4]

M12 x 1.5 0.47 [12] 0.059 [1.5] 0.492 [12.5]

M16 X 1.5 0.63 [16] 0.059 [1.5] 0.63 [16]

M20 X 1.5 0.79 [20] 0.059 [1.5] 0.79 [20]

M25 X 1.5 0.98 [25] 0.059 [1.5] 0.98 [25]

M32 X 1.5 1.26 [32] 0.059 [1.5] 1.26 [32]

M40 X 1.5 1.57 [40] 0.059 [1.5] 1.57 [40]

M50 X 1.5 1.97 [50] 0.059 [1.5] 1.97 [50]

M63 X 1.5 2.48 [63] 0.059 [1.5] 2.48 [63]

B 60°

- The most commonly used thread type

in the world
- The flank angle is 60°
A C
- Female and Male thread are both
parallel

Panzer-Gewinde (also Panzer-Rohr-Gewinde)

PG Threads
PG Nominal
Thread Size

A B C
Thread size major diameter Pitch Through Hole
in inches [mm] in inches [mm] in inches [mm]

PG 7 0.49 [12.5] 0.05 [1.27] 0.50 [12.7]

PG 9 0.60 [15.2] 0.056 [1.41] 0.606 [15.4]

PG 11 0.73 [18.6] 0.056 [1.41] 0.74 [18.8]

PG 13/13.5 0.80 [20.4] 0.056 [1.41] 0.8149 [20.7]

PG 16 0.89 [22.5] 0.056 [1.41] 0.897 [22.8]

PG 21 1.11 [28.3] 0.062 [1.59] 1.12 [28.6]

PG 29 1.46 [37] 0.062 [1.59] 1.47 [37.4]

PG 36 1.85 [47] 0.062 [1.59] 1.87 [47.5]

PG 42 2.13 [54] 0.062 [1.59] 2.14 [54.5]

PG 48 2.39 [59.3] 0.062 [1.59] 2.35 [59.8]

B 80°

- German thread type

- Depth of thread smaller than NPT or
Metric, but larger flank angle (80°)
A C
- Female and Male thread are both
parallel

SOURCES
https://www.sealconusa.com/catalog/e-srf-cat/49-Technical-Info-Thread-NPT-Metric-PG-BSPP.pdf
https://www.teesing.com/files/en/brochures/Type-of-thread.pdf

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