ASTM F1498-00
(Specification)Standard Specification for Taper Pipe Threads 60° for Thermoplastic Pipe and Fittings
Standard Specification for Taper Pipe Threads 60° for Thermoplastic Pipe and Fittings
SCOPE
1.1 This specification covers dimensions and gaging of taper pipe threads used on threaded plastic pipe and fittings.
1.2 Threads meeting this specification shall only be used on those plastic materials deemed suitable by the manufacturer.
1.3 Specialty threads or threads not requiring a leak-tight joint are not covered in this specification. Note 1-The terms "wrench makeup" and "wrench tight" are standard terminology for tightness and do not imply using a pipe wrench or other tools which would damage plastic pipe and fittings.
1.4 Thread Designations -The type of pipe threads included in this specification are designated by specifying in sequence the nominal pipe size, number of threads per inch, and the thread series symbols as follows in accordance with ANSI/ASME B1.20.1: 3/8-18 NPT. For left-hand threads add LH to the designation, otherwise right-hand threads will be understood. For example: 3/8-18 NPT-LH.
1.4.1 Each of these letters in the symbol has a definite significance as follows: N = National (American Standard) P = Pipe T = Taper
1.5 The values stated in inch-pound units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see 7.2.1 and 8.3.
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An American National Standard
Designation: F 1498 – 00
Standard Specification for
Taper Pipe Threads 60° for Thermoplastic Pipe and Fittings
This standard is issued under the fixed designation F 1498; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.1 This specification establishes requirements fordimen-
F 412 Terminology Relating to Plastic Piping Systems
sions and gaging of taper pipe threads used on threaded plastic
2.2 ANSI/ASME Standards:
pipe and fittings.
B 1.20.1 Pipe Threads, General Purpose (inch)
1.2 Threads meeting this specification shall only be used on
B 1.7M Nomenclature, Definitions and Letter Symbols for
those plastic materials deemed suitable by the manufacturer.
Screw Threads
1.3 Specialty threads or threads not requiring a leak-tight
B 47.1 Gage Blanks
joint are not covered in this specification.
NOTE 1—The terms “wrench makeup” and “wrench tight” are standard 3. Terminology
terminology for tightness and do not imply using a pipe wrench or other
3.1 Terminology is in accordance with Terminology F 412
tools which would damage plastic pipe and fittings. The terms “hand-
and abbreviations are in accordance with Terminology D 1600,
tight” and “hand-tight engagement” refer only to thread gaging (not pipe
unless otherwise indicated.
and fitting connections) and is the definition of the L gage length.
3.2 Nomenclature, definitions, and letter symbols for screw
1.4 Thread Designations—The type of pipe threads in-
threads are in accordance with ANSI/ASME B 1.7M.
cluded in this specification are designated by specifying in
sequence the nominal pipe size, number of threads per inch,
4. American National Standard Taper Pipe Thread Form
and the thread series symbols as follows in accordance with
4.1 Thread Form—The form of thread profile specified in
ANSI/ASME B 1.20.1: ⁄8-18 NPT. For left-hand threads add
this specification shall be known as the American National
LH to the designation, otherwise right-hand threads will be
Standard Taper Pipe Thread Form. The relations as specified
understood. For example: ⁄8-18 NPT-LH.
herein, for form of thread and general notations are shown in
1.4.1 Each of these letters in the symbol has a definite
Fig. 1.
significance as follows:
4.2 Angle of Thread—The angle between the sides of the
N = National (American Standard)
thread is 60° when measured in an axial plane. The line
P = Pipe
bisecting this angle is perpendicular to the axis.
T = Taper
4.3 Truncation and Thread Height—The height of the sharp
1.5 The values stated in inch-pound units are to be regarded
V thread, H, is as follows:
as the standard.
H 5 0.866025p 5 0.866025/n (1)
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
where:
responsibility of the user of this standard to establish appro-
p = pitch of thread, and
priate safety and health practices and determine the applica-
n = threads per inch.
bility of regulatory limitations prior to use. For specific
4.3.1 The basic maximum height of the truncated thread, h
precautionary statements, see 7.2.1 and 8.3.
(see Fig. 1) is based on factors entering into the manufacture of
cutting tools and the making of tight joints.
2. Referenced Documents
h 5 0.800p 5 0.800/n (2)
2.1 ASTM Standards:
The crest and root of pipe threads are truncated a minimum
D 1600 Terminology for Abbreviated Terms Relating to
of 0.033p. Maximum truncation for the crest and root of these
Plastics
pipe threads is in Table 1. The crests and roots of the external
This specification is under the jurisdiction of ASTM Committee F-17 on Plastic
Piping Systems and is the direct responsibility of Subcommittee F17.10 on Fittings. Annual Book of ASTM Standards, Vol 14.02.
Current edition approved April 10, 2000. Published July 2000. Originally Annual Book of ASTM Standards, Vol 08.04.
published as F 1498 – 94. Last previous edition F 1498 – 94. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 08.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1498 – 00
H = 0.866025p = height of 60° sharp V thread b = 1° 47 in. = thread taper angle for 1 16 taper
/
h = 0.800000p = height of thread on product f = depth of truncation at crest
c
p =1/n = pitch (measured parallel to axis) f = depth of truncation at root
r
n = number of threads per inch F = width of flat at crest
c
a = 30° = thread flank angle F = width of flat at root
r
NOTE 1—For a symmetrical straight screw thread, H = cot a/2n. For a symmetrical taper screw thread, H = (cot a − tan b tan a)/2n, so that the exact
value for an American National Standard Taper Pipe Thread is H = 0.865743p as against H = 0.866025p, the value given above. For an 8-pitch thread,
which is the coarsest standard taper pipe thread pitch, the corresponding values of H are 0.108218 and 0.108253 respectively, the difference being
0.000035 in. This difference being too small to be significant, the value of H = 0.866025p continues in use for threads of 0.750 in., or less, taper/ft on
the diameter.
FIG. 1 Basic Form of American National Standard Taper Pipe Thread
and internal threads may be truncated either parallel to the 4.4 Thread Starts—Machined—Feathered starts are pro-
pitch line or parallel to the axis. The sketches in Tables 2-6 give duced by a 45° chamfer on the first thread when the thread is
a sectional view of this standard thread form, which represents
cut with a tap or die. The depth of chamfer shall be from ⁄4 to
the truncated thread form by a straight line. However, when
1 ⁄4 thread deep (see Fig. 2(a)). Feathered starts are prone to
closely examined, the crests and roots of molded pipe threads
crossing and mutilation and shall not be molded.
appear slightly rounded.
F 1498 – 00
A
TABLE 1 Limits on Crest and Root Truncation of American National Standard External and Internal Taper Pipe Threads, NPT
Threads/ Height of
Truncation (f) Equivalent Width of Flat (F)
Height of Thread
in. Sharp V
(h)
Min Max Tolerance Min Max Tolerance
(n) Thread (H)
Max Min Formula Inch Formula Inch Formula Inch Formula Inch
123456789 10 11 12 13 14
27 0.03208 0.02963 0.02496 0.033p 0.0012 0.096p 0.0036 0.0024 0.038p 0.0014 0.111p 0.0041 0.0027
18 0.04811 0.04444 0.03833 0.033p 0.0018 0.088p 0.0049 0.0031 0.038p 0.0021 0.102p 0.0057 0.0036
14 0.06186 0.05714 0.05071 0.033p 0.0024 0.078p 0.0056 0.0032 0.038p 0.0027 0.090p 0.0064 0.0037
11.5 0.07531 0.06957 0.06261 0.033p 0.0029 0.073p 0.0063 0.0034 0.038p 0.0033 0.084p 0.0073 0.0040
8 0.10825 0.10000 0.09275 0.033p 0.0041 0.062p 0.0078 0.0037 0.038p 0.0048 0.072p 0.0090 0.0042
A
The basic dimensions of the American National Standard Taper Pipe Thread are given in inches to four and five decimal places. While this implies a greater degree
of precision than is ordinarily attained, these dimensions are so expressed for the purpose of eliminating errors in computations.
TABLE 2 ABS, CPVC, and PVC Reference Information
turn; see Fig. 2(b) and Fig. 2(c).) The pilot shall be included in
Nominal Pipe Minimum Wall-Thickness, in. Minimum Hub-Diameter, in.
the measurement of the thread length.
Size, in.
Schedule 80 DWV Schedule 40 Schedule 80
4.5.1 Taper starts on the first thread are formed by the thread
Pipe and DWV
rising from the minimum to maximum diameter while main-
⁄8 0.095 . . . 0.526 0.645
taining the 60° thread profile (see Fig. 2(b)). The length of rise
⁄4 0.119 . . . 0.672 0.840
shall not exceed ⁄8 turn (45°).
⁄8 0.126 . . . 0.821 1.000
⁄2 0.147 . . . 0.998 1.280
4.5.2 Blunt starts on the first thread are formed by the thread
⁄4 0.154 . . . 1.221 1.450
rising from the minimum to maximum diameter while main-
1 0.179 . . . 1.504 1.810
1 ⁄4 0.191 0.100 1.871 2.200 taining the 60° thread profile (see Fig. 2(c)). The length of rise
1 ⁄2 0.200 0.088 2.127 2.450
shall not be greater than twice the thread height. The blunt start
2 0.218 0.066 2.634 3.000
is the preferred thread start.
2 ⁄2 0.276 . . . 3.170 3.560
3 0.300 0.086 3.841 4.250
4.6 Plastic Threads—General—The minimum wall thick-
3 ⁄2 0.318 . . . 4.374 . . .
ness (see Table 2) for the threaded portion of a plastic pipe or
4 0.337 0.104 4.907 5.350
fitting depends upon the material and the application. If the
5 0.375 . . . 6.039 . . .
6 0.432 . . . 7.203 7.625
wall thickness is not specified in a pipe or fitting standard, the
8 0.500 . . . 9.320 . . .
manufacturer must determine the appropriate wall thickness.
10 0.593 . . . 11.614 . . .
12 0.687 . . . 13.786 . . .
4.7 Sealing—Where pressure-tight or leak-tight non-
pressure joints are required, it is intended that taper pipe
threads conforming to this specification be made up with a
sealant-lubricant. Conventional pipe-thread compounds, putty,
4.5 Thread Starts—Molded—Internal and external molded
linseed oil-base products, and unknown mixtures shall not be
threads shall begin with a taper or blunt start. A pilot shall be
used.
provided from the face of the fitting and at the entering end of
the external threads; it shall have a length to the start (flank) of
NOTE 2—Some TFE-fluorocarbon-paste compounds, even though they
1 3
the first thread, equal to ⁄2 to ⁄4 the width of the thread pitch,
are recommended by the manufacturer, may not be compatible with some
1to1 ⁄4 thread pitch to the centerline. (Thread pitch equals one plastics.
F 1498 – 00
A
TABLE 3 Basic Dimensions of American National Standard Taper Thread, NPT
NOTE 1—Wrench makeup modified for plastic.
Hand-tight Gage Engagement Effective Thread, External
Nominal Outside Pitch Diameter at
Threads/in. Pitch of Thread
B D
C
Pipe Size, Diameter of Beginning of Ex- Length (L ) Length (L )
1 2
Diameter Diameter
(n) (P)
in. Pipe (D) ternal Thread (E )
(E ) (E )
1 2
Inch Threads Inch Threads
1 2 3 4 5 6789 10 11
⁄16 0.3125 27 0.03704 0.27118 0.160 4.32 0.28118 0.2611 7.05 0.28750
⁄8 0.405 27 0.03704 0.36351 0.1615 4.36 0.37360 0.2639 7.12 0.38000
⁄4 0.540 18 0.05556 0.47739 0.2278 4.10 0.49163 0.4018 7.23 0.50250
⁄8 0.675 18 0.05556 0.61201 0.240 4.32 0.62701 0.4078 7.34 0.63750
⁄2 0.840 14 0.07143 0.75843 0.320 4.48 0.77843 0.5337 7.47 0.79179
⁄4 1.050 14 0.07143 0.96768 0.339 4.75 0.98887 0.5457 7.64 1.00179
1 1.315 11.5 0.08696 1.21363 0.400 4.60 1.23863 0.6828 7.85 1.25630
1 ⁄4 1.660 11.5 0.08696 1.55713 0.420 4.83 1.58338 0.7068 8.13 1.60130
1 ⁄2 1.900 11.5 0.08696 1.79609 0.420 4.83 1.82234 0.7235 8.32 1.84130
2 2.375 11.5 0.08696 2.26902 0.436 5.01 2.29627 0.7565 8.70 2.31630
2 ⁄2 2.875 8 0.12500 2.71953 0.682 5.46 2.76216 1.1375 9.10 2.79062
3 3.500 8 0.12500 3.34062 0.766 6.13 3.38850 1.2000 9.60 3.41562
3 ⁄2 4.000 8 0.12500 3.83750 0.821 6.57 3.88881 1.2500 10.00 3.91562
4 4.500 8 0.12500 4.33438 0.844 6.75 4.38712 1.3000 10.40 4.41562
5 5.563 8 0.12500 5.39073 0.937 7.50 5.44929 1.4063 11.25 5.47862
6 6.625 8 0.12500 6.44609 0.958 7.66 6.50597 1.5125 12.10 6.54062
8 8.625 8 0.12500 8.43359 1.063 8.50 8.50003 1.7125 13.70 8.54062
10 10.750 8 0.12500 10.54531 1.210 9.68 10.62094 1.9250 15.40 10.66562
12 12.750 8 0.12500 12.53281 1.360 10.88 12.61781 2.1250 17.00 12.66562
A
The basic dimensions of the American National Standard Taper Pipe Thread are given in inches to four or five decimal places. While this implies a greater degree of
precision than is ordinarily attained, these dimensions are the basis of gage dimensions and are so expressed for the purpose of eliminating errors in computations.
B
Also length of thin ring gage and length from gaging notch to small end of plug gage.
C
Also pitch diameter at gaging notch (hand-tight plane).
D
Also length of plug gage.
4.8 Thread Tightness—Wrench Makeup—Some lubricants the hand-tight L engagement threads. However, conformance
(PTFE pastes, silicones, etc.) may result in more finger-tight
to this specification requires that all basic design dimensions be
thread engagement than with sealants. The maximum recom-
met (within applicable tolerances) including extension of the
mended tightness is two turns past finger tight. Over tightening
thread elements (L − L ) to provide for wrench-tight makeup.
2 1
will produce hoop stresses greater than plastic can withstand,
Therefore, additional methods of gaging may be employed to
resulting in split fittings.
evaluate conformance to the basic design dimensions. When
additional methods of gaging are employed, they shall be
NOTE 3—When assembling metal and plastic threads, the preferred
method is plastic male threads to metal female threads. Cyclic heating and
agreed upon between the supplier and the purchaser. Because it
cooling may result in dripping leaks.
is known that injection molded threads that are removed from
4.9 Inspection—A gaging method of tolerances is pre- the mold before they are completely cooled will distort in form
scribed in this specification to effect a functional inspection of so that they will not gage properly, threads suspected of being
F 1498 – 00
TABLE 3 Basic Dimensions of American National Standard Taper Thread, NPT (continued)
Wrench Makeup Length for
Basic
Length, L Plane to L A B
1 2 Internal Thread
Overall
Increase in Minor
Plane External Thread Nominal Complete
Nominal Length
Diameter C Height of Diameter Diameter
(L −L ) Vanish Thread (V) External Thread
2 1
Pipe Size, Length (L ) External
(E ) Thread (h) per Thread at Small
in. Thread
(0.0625/n) End of
(L ) Length (L )Diameter
4 5
Inch Thread Inch Thread Inch Thread Pipe (K )
(E )
1 12131415161718192021222324
⁄16 0.1011 2.73 0.0741 2 0.26656 0.1285 3.47 0.3896 0.1870 0.28287 0.02963 0.00231 0.2416
⁄8 0.1024 2.76 0.0741 2 0.35889 0.1285 3.47 0.3924 0.1898 0.37537 0.02963 0.00231 0.3339
⁄4 0.1740 3.13 0.1111 2 0.47045 0.1928 3.47 0.5946 0.2907 0.49556 0.04444 0.00347 0.4329
⁄8 0.1678 3.02 0.1111 2 0.60507 0.1928 3.47 0.6006 0.2967 0.63056 0.04444 0.00347 0.5676
⁄2 0.2137 2.99 0.1429 2 0.74951 0.2478 3.47 0.7815 0.3909 0.78286 0.05714 0.00446 0.7013
⁄4 0.2067 2.89 0.1429 2 0.95876 0.2478 3.47 0.7935 0.4029 0.99286 0.05714 0.00446 0.9105
1 0.2828 3.25 0.1739 2 1.20277 0.3017 3.47 0.9845 0.5089 1.24543 0.06957 0.00543 1.1441
1 ⁄4 0.2868 3.30 0.1739 2 1.54627 0.3017 3.47 1.0085 0.5329 1.59043 0.06957 0.005
...
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