)AN AMERICAN NATIONAL STANDARD

PIPE THREADS, GENERAL PURPOSE (INCH)

ANS|/ASME 81.20.1-1g€Xl

12.3 Coated or Plated Threads. The threadedproduct specifications covered in this Standard donot include an allowance for coatings or plating.

1.3 Sealing

1.3.1 Where pressure-tight joints are required, it isintended that taper pipe threads conforming to thisStandard be made up wrench-tight with a sealant"

To prevent galling on certain piping materials such as

stainless steels, the sealant usually contains a lubricant"

1.3.2 Pipe threads designed for pressure-tightjoints that may be used without sealing compounds(Dryseal Threads) are covered in ANSI B1.20.3 (Inch)and ANSI Bl.2O.4 (Metric Transtation)"

1.4 lnspection

A gaging method and tolerances are prescribed inthis Standard to effect a functional inqpection ofthehandtight .L1 engagement threads. However, con-formance to this Standard requires that all basic

design dimensions be met (within applicable toler-ances) including extension of the thread elements toprovide for wrench-tight makeup. Therefore, addi-tional methods of gaglng may be employed toevaluate conformance to the basic design dimensions.When additional melhods of gaging are employed,they shall be agreed upon by the supplier and thepurchaser.

1.5 Appendix

Useful and supplementary information which isnot a part of this Standard is presented in the Appen-dix. Specifically, the Appendix gives Suggested TwistDrill Dameters for Drilled Hole Sizes for PipeThreads"

1.6 Related Standard

Definitions of terms and symbols for thread dimensions are given in ANSI 81.7, Nomenclature,Definitions and Letter Symbols for Screw Threads"

1 INTRODUCTION

1"1 Scope

This American National Standard covers dimen-sions and gaging of pipe threads for general purposeapplications.

'1.2 Thread Designations

1.2.1 The types of pipe threads included in thisStandard are designhtetl by specifying frt sequence

the nominal pipe size,l number of threads per inchand the tluead series symbol as follows:

3/8 - 18 NPTl/8 - 27 NPSC

tl2 -t4 NPTR" rl8 - 27 NPSM

l/8 - 27 NPSL1 - 1I.5 NPSH

For left hand threads add LH to the designation,otherwise right hand threads will be understood" Forexample:

3/8 - 18 NPT - LH

1.2.2 Each of these letters in the rymbols has adefinite significance as follows:

N = National (American) StandardP = PipeT = TaperC = CouplingS = StraightM = Mechanical

L = LocknutH = Hose CouplingR = Railing Fittings

rWhere it is necessary to use decimal notation for the sizedesignation (as when inserting such in a @mputer or elec-

tronic accounting machine) the decimal equivalent of nom-inal pipe size may be substituted for fractional pipe sizer

AN AMERICAN NATIONALPIPE THREADS, GENERAL

STANDARDPURPOSE IINCHI ANSUASME 81.20.'[-19&t

External Thread lnternal Thread

NOTATIONH= o-866025p=heishtof60deg.sharpvthread F = tdeg.47min.=threadtaperangreforr/16taper

q

n-\^/l c

'.( L

t - O.8OOOOQ = heightof threadonproductp G 17, = pitch {measured parallel to axis}n = number of threads per inchC"= 3Odeg. = threadflankangle

f" = depth of truncation at crestf. = depth of truncation at rootF" = width of flat at crestFr = width of flat at root

GENERAL NorE: For a symmetrical straight screw thread, H=cotgJ2n.Forarymmetrical tape-rscrewthread,H= {cotc-tan2 ptanall2n,sothattheexactvalueforanAmericanNationat s."no"rj'r"p"r;;;;;;;"=o.ruuroro".against ll = 0'86602$p, the value given above. For an Spitch thread, which is the coarsest standard taper pipe thread pitch,the corresponding values of H are o-1 o82l 8 and 0.1 08253 respectively, the difference being 0.00oo35 inch. Th is d ifferencebeing too small to be significant. the value of H = 0.866025p conrinues in use for threads of 0.750 in., or less. taper/ft onthe diameter.

FIG" 1 BASIC FORM OF AMERTCAN NATIONAL STANDARD TAPER PIPE THREB.[]

2 e

Tl,-i

9O des.

ttt

AN AMERICAN NATIONAL STANDARDPIPE THREADS, GENERAL PURPOSE (INCHI

Pitch line

ANSUASME 81.20.1-1983

{

E3

I

Taper of thread1 in 16 measuredon diameter

', I

Fo

I

TABLE 2 BASIC DIMENSIONS OF AMERICAN NATIONAL STANDARD TAPER PIPE THREAD, NPTT

NominalPipeSize

1

O.D. ofPipe(Dl

Threads/in.lnl

Pitch ofThrsad

lPl

Pitch Diam.at Beginningof ExternalThread (Fol

Handtight Engagement Effective Thr€ad, ExternalLength2 (Lr I

Diam.3(Erl

Lengrttra (tzlDiam"lEzlinch Threads inch Threads

2 3 4 5 6 7 8 9 10 11th,

kv,7"

v,- ,/o

1

1Y41Y22

14 0.D.l6 0.D"'I 8 0.D.20 0.D"24 0.D.

2th3

,tZ

5

68

10

l2

0.31 250"405

0.s400.67 5

, o.8401.050

1.3151.6601.9002.37s

2.87 S3.5004.0004.500

5.5 636-6258.625

10.750't2.7 50

14.00016.000'18.000

20.00024.000

11.5r 1.51 1.5I t-5

2727

18

l81414

8888

888

88

888

8

8

0.o37040.03704

0.055560.05556; l,'fJ .

o.071430.o7143

0.086960.086860.086960.08696

0. I 25000.1 25000.1 25000. t 2500

0.1 25000. I 25000. I 25000.1 25000.i 2500

0.1 25000.1 25000.'r 25000. I 25000.1 2500

o.27"t180.36351

0.477390.61201

0.758430.96768

1.213631.5571 3

1.796092.26902

2.719533.340623.837s04.33438

5.390736.446098.43359

10.5453112.s3281

1 3.7750015.7 62501 7.750001 9.7375023.712sO

0.1600.1 61 5

o.22780.240'o.320

0.339

0.400o.420o.4200.436

0.6820.7 660.821o.844

0.9370.9581.0631.2101.360

1.s621.8122.0002.1252.37 5

4.484.75

4.604.834.835.01

5.466.136.s76.7 5

7.507.668.509.68

10.88

12.5014.5016.0017.0019.00

4.324.36

4.104.32

0.281180.37360

o-491630.62701r r YY' -|. +. s' \0.77843 '

0.98887

1.238631.s83381.822342,29627

2.762163.388503.888814.38712 l

I

s.44s2s I

6.sose7 I

8.s0003 I

10.620s4 I

12.61781 I

13.87262 I

rs.8757s I

17.87s00 I

t e.87031 I

23.860e4 I

0.2611o.2639

0.40180.4078

0.53370.5457

0.68280.70680.72350.7 565

1.137 5

1.20001.2500,1.3000

1.40531.512st -71251.92502.1250

2.25002.45002.65002.85003.2s00

7.057.12

7.237.34

7.477.64

7.858.138.328.70

9.109.60

10.00t 0.40

11.2s12.1013.7015.40t 7.00

18.0019.6021.2022.8026.00

0.287 s00.38000

0.502500.63750

o.79't791.00179

1.2s6301.601301.841302.3"t630

2.790623.415623.915624.41562

s.478626.540628.54062

r 0.6656212.66562

13.9r56215"915 6217.9156219.9156223.91s62

€

NOTES:(1) The basic dimensions of the American National standard raper Pipe Thread are given in inches to four or five decimal prac€s. whire thisimplies a greater degree of preci5ion than is ordinarily attained. these dimensions are the basis of gage dimensions and are so expressed for thepurpose of eliminating errors in computations.(2) Also length of thin ring gage and rength.from gaging notch ro smat end of prug gage.(3) Also pitch diameter at gaging notch (handtigtrt planel.{4) Also lengrh of plug gage.

e

AN AMERICAN NATIONAL STANDARDPIPE THREADS, GENERAL PURPOSE (INCHI ANSUASME 81.2O.1.1983

TABLE 2 BASIC DTMENSIONS OF AMERICAN NATIONAL STANDARD TAPER PIPE THREAD, NPTI (CONT'D)

{5} The length t5 from the end of the pipe determines the plane beyond which the thread form is incomplete at the crest- The next two ihreadsare complete at the root. At this plane the cone formed by the crests of the thread intersects the cylinder forming the external surface o{ thepipe. L5 = Lz -2p.

(6) Given as information for use in selecting tap drills. (See Appendix).(7) Military Specification MIL-P-7105 gives the wrench makeup as three threads for sizes 3 and smaller. The €t dimensions are as follows:

Nominal pipe size 2rl = 2.696019 and size 3 = 3.31719; sizes 2 ard srnaller same as above, col. 16"

{8} Reference dimension.

Length, L1 Planeto L2 Plans

External ThreadLz - Lrl

Wrenci lt/hkeup Length.fortnternal Thread?

Vanish Threadtn

OvErall8Length

ExternalThread

lLq)

Nominhl CompleteExtornal Threads5

Heightof

Thread(n)

I ncreasein Diam./

Thread(0.062s/n)

Basic6Minor Diam"

.t SmallEnd of

Pipa (Ko)PipeSize

Lengtl lLrl Diam.(Frl

Length(Ls )

Diam.{€s Itn. Thread ln. Thread tn- Thread

1 12 13 14 t5 16 17 18 19 20 21 22 23 24

lo7"

t,ln

I

rltl/z2

2th

,y2

5

6

8

1012

It/t6Y"

14 0.D.16 0.D.i 8 0.D.20 0.D.24 0.D.

0.10.1 1

0"1 024

0.1 7400.r 678

o.21370.2067

0.28280.28680.30350.3205

0.4s550.43400.42900.4s60

0.46930.55450.64950.71500.7650

0.68800.6 3800.65000.72500.8750

2.732.76

3.t 33.02

2.992.89

3.643-473.433.65

3.253.303.493.69

3.7 S

4.44s.205.726-12

5-505.105.205.807.00

0.1 111

0.1 It10"r 6670.1 667:1,--i6.21430-2143

o.26090.26090.26090.2609

0.25000.25000.25000.2s00

0.25000.25000.25000.25000.2500

0.25000.25000-25000.25000.2500

3

3

3

3

3

3

3

3

3

3

2

2

2

2

'2

2

2

2

?

2

2

2

2

2

o.264240.35656

o.466970.601 60

o-7 45040.95429

1.r 97331.540831.779782.25272

2.703913.325003.82r 884.3 I 875

5.3751 1

6.430478.4179't

10-5296912.51719

r 3.759381 5.74688't7.73438

19.7218823.69688

0.12850.1 285

0.1 9280.1 928

0.24780.2478

0.30 r 7

0.30r 7

0.30170.301 7

0.43370.43370.43310.4337

0.43370.43310.43370.43370.4331

0.4337o.43370.43370.43370.4337

3.473.47

3.473.47

3.473-47

3.413.473.413.47

3.473.473.473.47

3.473.473-473.473.47

3.473-473.473.473.47

0.3896o.3924

0.59460.6006

0.78r s0.7935

0.98451.00851.02521.0582

1.sl121.6337r.68371.1337

1.84001.94622.146?2.3s812.5587

2-68372.88313.08373-28373.6837

0.1 8700.1 898

0.39090.4029

0.5089o.53290:54960.5826

0.88750-95001.00001.0500'l<l 5631.26251.46251.67501.8750

2.00002.20002.40002.60003.0000

o.2907o.2967

0.282810.37 537

0.495560.63056

0.78286

.0.99286

1.245431.590431.830432-30543

2.775003.400003.900004.40000

5.463006.525008.5 2500

r 0-550001 2.65000

13.900001 5.90000I 7.9000019.9000023.90000

0.029630,02963

o.o4444o.04444

0.057140.057't 4

0.069570.069570.0695 7

0.06957

0.1 000000.1 000000.r 000000.1 00000

0.1 000000.1 000000.1 000000.r 000000.1 00000

0.1 000000.1 000000.r 000000.1 000000.1 00000

0.002310.00231

0.0034;0.0034;

0.0044(0.0044(

0.0054:0.0054:0.0054:0.0054:

0.0078'0.0078'0.0078'0.o078'

0.00780.0078'0.00780.00780.0078

0.00780.00780.00780_0078

0.0078

0.24'.t60.3339

o.43290.s676

0.70130.91 05

't.14411.487 61.72652.1995

2.61953.24063.737 5

4"2344

5"29076.34618.33 36

10.445312.4128

13.675015.66251 7.650019.637 5

23-6125

AN AMER ICAN NATIONAL STANDARDPIPE THREADS, GENERAL PURPOSE (INCHI

The illustrbtion shows standard designfor sizes 2'inch and smaller. Largersizes are of slightly diflerent designs.

ANS|/ASME 81.20.r-1983

Basic Size Max. Size Min. Size

Pluggage

Taper of I

thread 1 in 16measured ondiametet

L1eo-__!

FIG" 4 NPT STANDARD TAPER PIPE THREADPLUG AND RING GAGES

Basic Size Max. Size

FIG.7 GAGING INTERNAL TAPER

FIG.6 GAGING EXTERNAL TAPER THREADSWITH RING GAGE

(0,

0.1 16p

Roots sharpor undercut(form optional)

Roors must clear O.O3glp flat i

FIG" 5 SUGGESTED FORM OF GAGE THREADMin. Size

THREADS

One turn large

Flush

Crests rruncateO pdr Z.t.t

l4

tI