Home
Blog
NPTF Pipe Thread

NPTF Pipe Thread

NPTF Thread in Hydraulic Connections

NPTF Hydraulic Fittings	Features	Compliance
Pipe Coupling	Female Pipe Thread	SAE 140138
Pipe Reducer	Male / Female Pipe Thread	SAE 140140
Pipe Nipple	Male Pipe Thread	SAE 140137
Male Pipe Elbow	Male Pipe Thread	SAE 140237*
Street Elbow	Male / Female Pipe Thread	SAE 140239

ASME B 1.20.3 NPTF Pipe Thread Specification
NPTF Pipe Thread Dimensions
Purpose of NPTF Threads
1 - 11 1/2 NPTF External Thread Drawing
1 - 11 1/2 NPTF External Basic Thread Dimensions
1 - 11 1/2 NPTF Internal Thread Drawing
1 - 11 1/2 NPTF Internal Basic Thread Dimensions
How to select the right thread type for your application?
NPTF Thread GG Series
NPTF Coupling Sizes
Comparison Between American Pipe Threads
NPTF Brass Pipe Fittings Types
1 - 11 1/2 NPTF Pipe Thread Tolerances
NPTF Pipe Dimensions
NPTF Pipe Thread Installation Torque Table
Torque Values for NPTF Threads
Assembly Instruction for NPTF Pipe Threads
Difference Between NPT vs NPTF
NPTF American Taper Pipe Thread Dimensions
NPTF Pipe Gages
Truncation and Height Tolerances of NPTF Thread
Designations of Dryseal Pipe Thread
National Pipe Thread Fuel Nominal Size

ASME B 1.20.3 NPTF Pipe Thread Specification

NPTF	National Pipe Taper Fuel
Other Name	Dryseal Tapered Pipe Thread
Material	Steel
Standard	ANSI/ASME B1.20.3
Compatible Fluid	Oil
Operating Temperature Range(°C)	-65～500 °F
Maximum Operating Pressure(MPa)	4,000 psi
NPTF Gages	L1, L2, L3
NPTF Classes	Class 1 Threads Class 2 Threads
Angle Tolerance	0.3°
Coating	AlTiN Coating
Applications	Hydraulic Systems Pneumatic Equipment Fuel Lines

NPTF Pipe Thread Dimensions

Thread Size	Nominal Size(in)	Nominal Male Thread (OD)(in)	Number of Threads per Inch
1	1/16	0.313	27
2	1/8	0.405	27
4	1/4	0.540	18
6	3/8	0.675	18
8	1/2	0.840	14
12	3/4	1.050	14
16	1	1.315	11.5
20	1-1/4	1.660	11.5
24	1-1/2	1.900	11.5
32	2	2.375	11.5
40	2-1/2	2.875	8
48	3	3.500	8
64	4	4.500	8

Purpose of NPTF Threads

Prevent Leaks in Sensitive Systems
Ensure Metal-to-Metal Contact
Durability in High-Pressure Environments

NPTF is Not Interchangeable with NPT or NPS, Check ASME B 1.20.3 Thread Advantages

Self-Sealing
Dryseal Connection
Standardization
Tapered Thread
High Pressure and Temperature Resistance

1 - 11 1/2 NPTF External Thread Drawing

Overview Drawing

Profile Drawing

1 - 11 1/2 NPTF External Basic Thread Dimensions

Property	mm	Inch
Nominal Pipe Size(∅)	-	1
Length of Vanish threads (V)	6.469	0.25470
Hand-Tight Engagement Length (L1)	10.16	0.40000
Root Truncation (fr)	0.165	0.0065
Pitch Diameter at L2 plane (E2)	31.91	1.25630
End of Thread Pitch Diameter (E0)	30.826	1.21363
Pitch - Distance (P)	2.2087	0.086957
Pipe Outside Diameter (D)	33.4	1.315
Length of Last usefull Thread (L2)	17.343	0.68280
Height of sharp V (H)	1.913	0.075310
Thread Height (h)	1.637	0.06446
Overall Thread Length (L2 + 3P)	23.813	0.93750
Crest Truncation (fc)	0.11	0.00435
Fitting Outside Diameter (D2)	33.71	1.327
Pitch Diameter at L1 plane (E1)	31.461	1.23863
Thread Tapper Angle (β)	-	1.7893 °
Thread V half Angle (α)	-	30 °
Pitch - TPI (P)	-	12

1 - 11 1/2 NPTF Internal Thread Drawing

Overview Drawing

Profile Drawing

1 - 11 1/2 NPTF Internal Basic Thread Dimensions

Property	mm	Inch
Nominal Pipe Size(∅)	-	1
Pitch Diameter at L3 plane (E3)	30.411	1.19730
Pitch Diameter at the end of the thread (E1)	31.461	1.23863
Pitch - TPI (P)	-	12
Hand-Tight Engagement Length (L1)	10.16	0.40000
Thread V half Angle (α)	-	30 °
Thread Height (h)	1.637	0.06446
Height of sharp V (H)	2.209	1.3270
Length of Wrenching Allowance (L3)	6.627	0.26090
Root Truncation (fr)	0.165	0.0065
Pitch - Distance (P)	2.2087	0.086957
Crest Truncation (fc)	0.11	0.00435
Ideal Tap Drill Size	28.931	1.13900
Thread Tapper Angle (β)	-	1.7893 °
Nearest standard Inch drill	-	1 9/64 (1.141)

How to select the right thread type for your application?

Consider the System’s Location and Standard
Determine Pressure and Fluid Requirements
Understand the Materials and Corrosive Factors
Matching Thread Types

NPTF Fittings Thread Standard

Threads	Standards
NPTF Thread	ANSI B 1.20.3
Metric ISO Thread	DIN 13
Unified National (UN) Threads	UNF, UNEF, UNC
Trapezoidal Threads	ACME and TR
Whitworth Threads	BSF and BSW

NPTF Thread GG Series

1/2 GG-S
1 1/4 GG-S
1 GG-S
1/4 GG-S
1/4 X 1/8 GG-S
1/2 X 1/4 GG-S
1/2 X 3/8 GG-S

NPTF Coupling Sizes

Tube Fitting Part #	End Size		C HEX (in.)	L (in.)	W (in.)	W1 (in.)	Dynamic Pressure (x 1,000 PSI)
Tube Fitting Part #	1 NPTF	2 NPTF	C HEX (in.)	L (in.)	W (in.)	W1 (in.)	-S	-SS	-B
1/4 GG	1/4 - 18	1/4 - 18	3/4	1.13	0.75	0.75	6.0	6.0	3.9
1/8 GG	1/8 - 27	1/8 - 27	5/8	0.75	0.63	0.63	6.0	6.0	3.9
1/4 X 1/8 GG	1/4 - 18	1/8 - 27	3/4	0.94	0.63	0.75	6.0	6.0	3.9
3/8 X 1/4 GG	3/8 - 18	1/4 - 18	7/8	1.13	0.75	0.88	6.0	6.0	3.9
3/8 X 1/8 GG	3/8 - 18	1/8 - 27	7/8	1.03	0.63	0.88	6.0	6.0	3.9
3/8 GG	3/8 - 18	3/8 - 18	7/8	1.13	0.88	0.88	6.0	6.0	3.9
1 GG	1 11 1/2	1 - 11 1/2	1 5/8	1.89	1.63	1.63	3.0	3.6	1.9
1/2 GG	1/2 - 14	1/2 - 14	1 1/8	1.50	1.13	1.13	5.0	6.0	3.2
1/2 X 1/4 GG	1/2 - 14	1/4 - 18	1 1/8	1.38	0.75	1.13	5.0	6.0	3.2
1/2 X 1/8 GG	- 1/2 - 14	- 1/8 - 27	1 1/8	1.06	0.63	1.13	6.0	6.0	3.2
1/2 X 3/8 GG	1/2 - 14	3/8 - 18	1 1/8	1.50	0.88	1.13	5.0	6.0	3.2
3/4 X 1/4 GG	3/4 - 14	1/4 - 18	1 3/8	1.55	0.75	1.36	4.0	4.8	3.1
3/4 X 1/2 GG	3/4 - 14	1/2 - 14	1 3/8	1.88	1.13	1.36	4.0	4.8	3.1
3/4 GG	3/4 - 14	3/4 - 14	1 3/8	1.53	1.38	1.38	4.0	4.8	2.6
1 X 1/2 GG	1 11 1/2	1/2 - 14	1 5/8	1.77	1.13	1.63	3.0	3.6	1.9
1 X 3/4 GG	1 11 1/2	3/4 - 14	1 5/8	1.77	1.38	1.63	3.0	3.6	1.9
1 1/4 GG	1 1/4 - 11 1/2	1/4 - 11 1/2	2	1.93	2.00	2.00	2.5	3.0	1.9
1 1/4 x 1 GG	1 1/4 11 1/2	1 - 11 1/2	2	1.93	1.63	2.00	2.5	3.0	1.9
1 1/2 GG	1 1/2 - 11 1/2	1/2 - 11 1/2	3/8	1.93	2.38	2.38	2.0	2.4	1.5
1 1/2 X 1 1/4 GG	1 1/2 - 11 1/2	1/4 - 11 1/2	3/8	1.93	2.37	2.37	2.0	2.4	1.5
2 GG	2 11 1/2	2 11 1/2	7/8	1.97	2.88	2.88	2.0	2.4	1.5

Comparison Between American Pipe Threads

Pipe Threads	NPTF	NPT	NPSC	NPSF	NPSM	NPSL	NPSI
Standards	ANSI B1.20.3	ANSI B1.20	ANSI B1.20	ANSI B1.20.3	ANSI B1.20	ANSI B1.20	ANSI B1.20.3
Internal Thread	Taper	Taper	Cylindrical	Cylindrical	Cylindrical	Cylindrical	Cylindrical
External Thread	Taper	Taper	Taper (=NPT)	Taper (=NPTF)	Cylindrical	Cylindrical	Cylindrical (=NPT-SAE / NPTF)
Applications	Drysealing	General Applications, Non-sealing	General Applications, Non-sealing	Drysealing	fastening thread Non-sealing	Locknut, Non-sealing	Drysealing

NPTF Brass Pipe Fittings Types

Brass NPTF Ballseat Adapter

Brass NPTF Pipe Cap

NPTF Slotted Head Plug

Brass NPTF Hex Head Plug

Countersunk Hex Head Plug

Brass NPTF Pipe Extender

Hex Pipe Reducer Bushing

Brass NPTF Female Union

Brass NPTF Female Coupling

Brass NPTF 45° Street Elbow

Brass NPTF Male Branch Tee

Brass NPTF Female Cross

1 - 11 1/2 NPTF Pipe Thread Tolerances

Property	Root Truncation (fr)	Thread Height (h)	Tapper Angle (β)	Crest Truncation (fc)	Thread Head half Angle(α)
Min	0.00520" (0.132 mm)	0.062310" (1.583 mm)	1.643°	0.00350" (0.089 mm)	28.5°
Max	0.00780" (0.198 mm)	0.066610" (1.692 mm)	1.934°	0.00520" (0.132 mm)	31.5°

NPTF Pipe Dimensions

Thread Identifier	Diameter Outside mm	Diameter Outside inch	Gears per Inch	Diameter Core Hole at Thin Tube End mm	Pitch mm
1/4" - 18	13,577	0,534	180	1,070	1,411
3/8" - 18	17,016	0,670	180	1,410	1,411
l" - 111/2	33,195	1,307	115	2,850	2,209
11/4" - 111/2	41,952	1,652	115	3,700	2,209
11/2" - 111/2	48,021	1,890	115	4,350	2,209
2·- 111/2	60,060	2,364	115	5,500	2,209
2 1/2" - 8	72,642	2,860	80	6,550	3,175
1/2" - 14	21,211	0,835	140	1,740	1,814
3/4" - 14	26,566	1,046	140	2,260	1,814
1/ 16" -27	7,870	0,310	270	600	0,940
1/8" -27	10,217	0,402	270	825	0,940
4" -8	1,13,913	4,485	80	10,700	3,175

NPTF Pipe Thread Installation Torque Table

Pipe Thread Size NPTF	T.F.F.T.
1/2 -14	2 - 3
1/4 - 18	2 - 3
1/8 - 27	2 - 3
3/4 - 14	2 - 3
3/8 - 18	2 - 3
1 - 11 1/2	1.5 - 2.5
1 - 11 1/4	1.5 - 2.5
2 - 11 1/2	1.5 - 2.5

Torque Values for NPTF Threads

Size	in-lbs	Newtons-m
1/2"	30	3.39
1/4"	16	1.81
1/8"	7.0	0.79
1/16"	5.0	0.57
3/4"	54	6.10
3/8"	23	2.60
1"	78	8.81

Assembly Instruction for NPTF Pipe Threads

Assembly Torque for Pipe Threads and Adapter Unions

Pipe Size	Pipe			Adapter Unions
Pipe Size	Ft. Lbs. Max.	Nm. Max.	Tapered Pipe T.F.F.T. (Turns)	Ft. Lbs. Max.	Nm. Max.
1/2	54	73	1/2-1 1/2	47	64
1/4	25	34	3/4-1 3/4	20	27
1/8	12	16	3/4-1 3/4	13	18
3/4	78	106	1/2-1 1/2	84	114
3/8	40	54	3/4-1 3/4	25	34
1	112	152	1/2-1 1/2	129	175
1-1/2	211	286	1/2-1 1/2	152	206
1-1/4	154	209	1/2-1 1/2	152	206
2	300	407	1/2-1 1/2	300	407

Dryseal Pipe Thread for Leak-proof Connection

Required Installation Steps for Strong, Leak-free Connections

Check male and female threads
Clean burs and nicks
Gauge threads per standard
Hand-tighten the fitting
Count and mark exposed threads
Apply sealant/lubricant to male threads
Hand-tighten to dry-fit position
Wrench-tighten the joint
For shaped fittings, tighten as needed for orientation

Difference Between NPT vs NPTF

-	Width of Flat of Profile		Height of Profile
P [G/"]	min.	max.	min.	max.
8	0,122	0,229	2,356	2,540
11,5	0,084	0,185	1,590	1,767
14	0,069	0,163	1,288	1,451
18	0,053	0,145	0,974	1,129
27	0,036	0,104	0,634	0,753

-	Width of Flat of Profile
-	ground		top
P [G/"]	min.	max.	min.	max.
8	0,203	0,279	0,152	0,203
11,5	0,152	0,229	0,102	0,152
14	0,127	0,178	0,076	0,127
18	0,127	0,178	0,076	0,127
27	0,102	0,152	0,051	0,102

NPTF Threads Used in JIC/ SAE Hydraulic Fittings

Hydraulic Systems
Fuels
Air and Inert Gases
Piping Systems
High Pressure Applications
CO2 and Nitrogen Beverage Gas Lines
Pneumatics
Vacuum

NPTF American Taper Pipe Thread Dimensions

Nominal Diameter	Tapping Drill Sizemm	Major Diameter mm	Pitc hmm	TPI
1/2" - 14	17.40	21.211	1.814	14
1/4" - 18	10.70	13.577	1.411	18
1/8" - 27	8.25	10.217	0.940	27
1/16" - 27	6.00	7.870	0.940	27
3/4" - 14	22.60	26.566	1.814	14
3/8" - 18	14.10	17.016	1.411	18
1" - 11 1/2	28.50	33.195	2.209	11.5
1 1/2" - 11 1/2	43.50	48.021	2.209	11.5
1 1/4" - 11 1/2	37.00	41.952	2.209	11.5
2" - 11 1/2	55.00	60.060	2.209	11.5
2 1/2" - 8	65.50	72.642	3.175	8
4" - 8	107.00	113.913	3.175	8

NPTF Pipe Gages

Gaging Internal Threads

Gaging External Threads

Truncation and Height Tolerances of NPTF Thread

TPI	Head Angle	Thread Height		Root Truncation		Crest Truncation
TPI	2α (60°)	hmin	hmax	fmin	fmax	fmin	fmax
8	+/- 1.5°	0.09185	0.09615	0.0069	0.0095	0.0052	0.0069
11.5	+/- 1.5°	0.06231	0.06661	0.0052	0.0078	0.0035	0.0052
14	+/- 2°	0.0514	0.0549	0.0043	0.0061	0.0026	0.0043
18	+/- 2°	0.03771	0.04121	0.0043	0.0061	0.0026	0.0043
27	+/- 2.5°	0.02338	0.02688	0.0035	0.0052	0.0017	0.0035

Designations of Dryseal Pipe Thread

D: Nominal Diameter
P: Pitch
S: Series
R/L: Direction

National Pipe Thread Fuel Nominal Size

Inch Size	Nominal Thread Size	Male Thread OD	Female Thread ID	Dash Size
1/2	1/2· 14	27/32 (0.84)	25/32 (0.77)	08
1/4	1/4·18	11/32 (0.S4)	1/2(0.49)	04
1/8	1/8-27	12/32 (0.41)	3/8(0.38)	02
3/4	3/4·14	1 1/16( 1.0S)	1 (0.98)	12
3/8	3/8- 18	11/16 (0.68)	5/8 (0.63)	06
1	1 - 11 1/2	15116(1.32)	11/4 (1.24)	16
11/2	1 1/2·11 1/2	1 29/32 (1.90)	113/16(1..82)	24
11/4	1 1/4- 11 1/2	121132 (1.66)	1 19132 (1.58)	20
2	2 - 11 1/2	2 3/8 (2.38)	2 5/l6 (2.30)	32