INTERNATIONAL Is0
STANDARD 7-1
Third edition
1994-05-I 5
Pipe threads where pressure-tight joints
are made on the threads -
Part 1:
Dimensions, tolerances and designation
Filetages de tuyauterie pour raccordement avec Gtanchbitb dans le
filet -
Partie 1: Dimensions, tokrances et d&ignation
Reference number
IS0 7-l :I 994(E)
IS0 7=1:1994(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 7-l was prepared by Technical Committee
lSO/lC 5, Ferrous metal pipes and metallic fittings, Subcommittee SC 5,
Threaded or plain end butt-welding fittings, threads, gauging of threads.
This third edition cancels and replaces the second edition (IS0 7-1:1982),
which has been technically revised.
IS0 7 consists of the following parts, under the general title Pipe threads
where pressure-tight joints are made on the threads:
- Part 1: Dimensions, tolerances and designation
- Part 2: Verification by means of limit gauges
Annex A of this part of IS0 7 is for information only.
0 IS0 1994
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
INTERNATIONAL STANDARD 0 IS0 IS0 7=1:1994(E)
Pipe threads where pressure-tight joints are made on
the threads -
Part 1:
Dimensions, tolerances and designation
1 Scope maintain registers of currently valid International
Standards.
This part of IS0 7 specifies the requirements for
thread form, dimensions, tolerances and designation IS0 7-2: 1982, Pipe threads where pressure-tight
for jointing pipe threads, sizes 1 /I6 to 6 inclusive, for joints are made on the threads - Part 2: Verification
joints made pressure-tight by the mating of the by means of limit gauges.
threads. These threads are taper external, parallel
internal or taper internal and are intended for use with
pipes suitable for threading and for valves, fittings or 3 Definitions
other pipeline equipment interconnected by threaded
joints. For the purposes of this part of IS0 7, the following
definitions apply (see also figures 3 and 5).
An appropriate jointing medium should be used on the
thread to ensure pressure-tight joints. 3.1 gauge diameter: Major diameter of the thread,
whether external or internal.
NOTES
1 Parallel external pipe threads are not suitable as jointing 3.2 major cone: Imaginary cone which just touches
threads. the crests of a taper external thread or the roots of a
taper internal thread.
2 For pipe threads where pressure-tight joints are not
made on the threads, see IS0 228-l. 3.3 gauge plane: Plane, perpendicular to the axis
of the taper thread, at which the major cone has the
3 IS0 7-2 gives details of methods of verification of joint-
ing thread dimensions and form and recommended gauging gauge diameter.
systems.
NOTE 4 For external threads the gauge plane is located
at a distance equal to the nominal gauge length from the
small end of the thread. For internal threads the gauge plane
2 Normative reference is located at a distance of half-pitch behind the face of the
threaded part. This is in order to give consideration to the
The following standard contains provisions which, start of the thread that has been removed by chamfering.
through reference in this text, constitute provisions
of this part of IS0 7. At the time of publication, the 3.4 gauge length: On an external thread, the dis-
edition indicated was valid. All standards are subject tance from the gauge plane to the small end of the
to revision, and parties to agreements based on this thread.
part of IS0 7 are encouraged to investigate the pos-
sibility of applying the most recent edition of the 3.5 reference plane: Visible surface of each of the
standard indicated below. Members of IEC and IS0 internally and externally threaded parts, which facili-
1
IS0 7-1:1994(E) 0 IS0
tates the reading of the gauge when the thread is in- P Pitch
spected.
H Height of the triangle of the thread profile per-
For internal threads it is the face of the internally pendicular to the thread axis
threaded part, for external threads it is the small end
of the externally threaded part. h = 0,640 327 P; height of the thread profile be-
tween rounded crests and roots perpendicular
3.6 complete thread: That part of the thread which to the thread axis
is fully formed at both crest and root.
Y Radius of rounded crests and roots
NOTE 5 When there is a chamfer at the start of the
D Major diameter of the internal thread at the
thread not exceeding one pitch in length, this is included in
the length of complete thread. gauge plane (gauge diameter - see 3.1)
Dl D - 1,280 654 P; minor diameter of the internal
3.7 incomplete thread: That part of the thread
thread at the gauge plane
which is fully formed at the root, but truncated at the
crest by its intersection with the cylindrical surface of D - 0,640 327 P; pitch diameter of the internal
the product. thread at the gauge plane
38 washout thread; vanish thread: That part of d Major diameter of the external thread at the
the t hread which is not fully formed at the root. gauge plane (gauge diameter - see 3.1)
NOTE 6 The washout thread is produced by the bevel at 4 = d - 1,280 654 P; minor diameter of the ex-
the start of the threading tool. ternal thread at the gauge plane
3.9 useful thread: Complete thread plus incomplete d2 = d - 0,640 327 P; pitch diameter of the ex-
thread, excluding the washout thread. ternal thread at the gauge plane
3.10 fitting allowance: Length of useful thread be- Tl Tolerance on the gauge length of an external
yond the gauge plane of an external thread required thread
to provide for assembly with an internal thread at the
upper limit of the tolerance. T2 Tolerance for the position of the gauge plane on
an internal thread
NOTE 7 Internally threaded parts will have a sufficient
length to accommodate the fitting allowance, except when
5 Dimensions
they have a free run-out. See 7.2.2.
Pipe thread dimensions, in millimetres, are given in
3.11 wrenching allowance: Length of useful thread
table 1.
which is provided to accommodate the relative
movement between the end of the externally
threaded part and the internally threaded part required
for wrenching beyond the position of handtight en- 6 Designation
gagement.
The designation of threads according to this part of
IS0 7 shall consist of the following elements in the
sequence given:
4 Symbols
6.1 The description block shall be:
Rp Parallel internal pipe thread where pressure-tight
joints are made on the threads Pipe thread
Rc Taper internal pipe thread where pressure-tight
joints are made on the threads 6.2 The International Standard number block shall
be ..
R Taper external pipe thread where pressure-tight
joints are made on the threads IS0 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Tolerance on
Length of useful
position of
Diameters at gauge plane Gauge length (external thread) external thread not
gauge plane on
less than
internal thread
z
CE z .E zg i$ f$ Diametral
.I0 ‘; Height Major *- c tolerance1 1
54 EE E 2 9~ 2 gE 2 Fitting
ti;u $ 9 T Pitch of Pitch Minor Nominal Tolerance max. min. Tolerance on parallel
&zl
(gauge Es E& ‘gg allowance
Z 2 72% thread diameter) I!I 7-42 3~ &I2 5= internal
‘Q)w z* 5 ii 5s
n Lz LUJ Lo3 threads
Turns Turns Turns -I
P h d 4. 4 2) of 2) of 2) of
thread thread thread
&
(D
l/16 28 0,907 0,581 7,723 7,142 6,561 4 089 1 4,9 3,l I,1 1 l/4 6,5 7,4 5,6 2,5 2 314 + 0,071 a
l/8 28 0,907 0,581 9,728 9,147 8,566 4 019 1 4,9 3,l ItI 1 l/4 6,5 7,4 5,6 2,5 2 314 + 0,071
w 19 1,337 0,856 13,157 12,301 11,445 6 L3 1 7,3 4,7 L7 1 l/4 9,7 11 8,4 3,7 2 314 + 0,104 I
3/8 19 1,337 0,856 16,662 15,806 14,950 6,4 I,3 1 7,7 5,l 187 1 l/4 IO,1 11,4 8,8 3,7 2 314 * 0,104
-I=r
112 14 1,814 1,162 20,955 19,793 18,631 82 13 1 10,O 6,4 23 1 l/4 13,2 15 11,4 5,0 2 314 + 0,142 is
314 14 1,814 1,162 26,441 25,279 24,117 93 13 1 11,3 7,7 23 1 l/4 14,5 16,3 12,7 5,0 2 314 + 0,142
E
1 11 2,309 1,479 33,249 31,770 30,291 IO,4 1 12,7 8,l 289 1 l/4 16,8 19,l 14,5 6,4 2 314 f 0,180
23 e-.
II/4 11 2,309 1,479 41,910 40,43 1 38,952 12,7 23 1 15,0 IO,4 2,9 1 l/4 19,l 21,4 16,8 6,4 2 314 + 0,180 3
II/2 11 2,309 1,479 47,803 46,324 44,845 12,7 23 1 15,0 IO,4 2,9 1 l/4 19,l 21,4 16,8 6,4 2 314 + 0,180 !!w
I.
2 11 2,309 1,479 59,614 58,135 56,656 15,9 2,s 1 18,2 13,6 2,9 1 l/4 23,4 25,7 21,l 7,5 3 l/4 + 0,180
21/z 11 2,309 1,479 75,184 73,705 72,226 17,5 3,5 1 l/2 21,0 14,0 3,5 1 l/2 26,7 30,2 23,2 9,2 4 &- 0,216 2w
3 11 2,309 1,479 87,884 86,405 84,926 20,6 3,5 1 l/2 24,l 17,l 3,5 1 l/2 29,8 33,3 26,3 9,2 4 + 0,216
4 11 2,309 1,479 113,030 111,551 110,072 25,4 3,5 1 l/2 28,9 21,9 3,5 1 l/2 35,8 39,3 32,3 IO,4 4 l/2 + 0,216
5 11 2,309 1,479 138,430 136,951 135,472 28,6 3,5 1 l/2 32,l 25,l 3,5 1 l/2 40,l 43,6 36,6 11,5 5 + 0,216
6 11 2,309 1,479 163,830 162,351 160,872 28,6 3,5 1 l/2 32,l 25,l 3,5 1 l/2 40,l 43,6 36,6 11,5 5 + 0,216 CJ
-.
3
NOTE - The main dimensions were converted into millimetres on the basis of 1 inch = 25,4 mm, beginning with the number of threads per inch, which determines the pitch P, the formula h (the height CD
of thread) = 0,640 327 P and the major diameter at the gauge plane. Pitch diameter and minor diameter were then compiled by subtracting once or twice respectively the height of thread h from the major 2-.
diameter 0
5
-.
The nominal gauge length, the tolerances and the fitting allowance were directly computed. The remaining lengths given in table 1 were obtained by subtracting or adding the tolerances or fitting allowance
respectively to the nominal gauge length. Tolerances and fitting allowance are expressed in millimetres and in number of turns of thread. ;-.
-
=:
1) For parallel internally threaded parts the diametral tolerances are derived from the tolerances in column 14 by multiplying with the corresponding pitch in column 3 and with I/16, the amount of taper. 3
CD
r:
2) Informative tolerances, in millimetres, are obtained from the mandatory values in turns of thread by multiplying with the corresponding pitch in column 3 and rounding to the nearest 0,l mm.
2:
0 IS0 IS0 7=1:1994(E)
7.1.3 Direction of thread helix threads with free run-out shall be not less than 80 %
of the values given in column 17 of table 1. (See
Unless otherwise specified, the IS0 7-l thread shall figure 4.)
be a right-hand thread. (See also 6.4.)
8 Gauging
7.2 Thread lengths
For the verification of pipe threads, the plug and ring
7.2.1 External thread gauges used shall conform to IS0 7-2. The gauging
always relates to a reference plane of the threaded
The terms relating to the external taper pipe thread part to be verified (see figure5).
are given in figure3.
The length of the useful thread, allowable in practice,
9 Combination with fastening thread
is the sum of the lengths of the complete and in-
The combination of an external parallel thread G, tol-
complete threads, excluding the washout thread. The
erance class A or B in accordance with IS0 228-1,
minimum length of the useful thread must be not less
with an internal parallel thread Rp in accordance with
than the minimum gauge length plus the fitting al-
IS0 7-l needs special consideration.
lowance.
When it is necessary to have this combination, the
7.2.2 lnterna I thread positive or negative tolerance of the internal thread to
IS0 7-l shall be considered in the relevant product
The design of nternally threaded parts shall be such standards, where external parallel threads G are used.
that they can receive external threads up to the
lengths given in column 16 of table 1. The minimum Such a combination of threads may not necessarily
lengths Lmin of useful thread in the case of internal achieve a leak-tight joint.
r Reference plane
Complete
Useful
thread
thread
Incomplete thread
- Washout
thread
E
d
“a
-v------P
&
ii
L!J
- (T,/Z)/ ~
Gauge length
L- Major cone
I Allowanceequivalentto positive
-tolerance on-internal thread
Figure 3 - Terms relating to external threads
IS0 7-1:1994(E) Q IS0
Free run-out Freerun-out-
qrlj L min
Figure 4 - Internal threads with free run-out
Useful thread '
Reference plane
4 ’ 4 0,SP
Gauge plane
Internal parallel thread
Chamfer
Reference plane
i‘\-- Gauge plane
Tolerance for position of
- (T2’2’+ ‘: I_+ (T2/2)
gauge plane on internal
threads
External taper thread
Reference plane
Useful thread
Figure 5 - Illustration of internal and external pipe threads (position of gauge plane, reference plane
useful thread)
IS0 7=1:1994(E)
Annex A
(informative)
Bibliography
[I] IS0 228-l : 1994, Pipe threads where pressure-tight joints are not made on the threads - Part 1: Dimen-
sions, tolerances and designa bon.
