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IS0
INTERN AT1 ON AL ORGAN I Z AT I ON FOR STA N DARD I Z AT1 O N
IS0 RECOMMENDATION
R 263
IS0 INCH SCREW THREADS
GENERAL PLAN AND SELECTION FOR SCREWS, BOLTS AND NUTS
(diameter range 0.06 to 6 in)
1st EDITION
July 1962
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 263, IS0 Inch Screw Threads. General Plan and Selection
for Screws, Bolts and Nuts. (diameter range 0.06 to 6 in), was drawn up by Technical Committee
ISO/TC 1, Screw Threads, the Secretariat of which is held by the Sveriges Standardiseringskommis-
sion (SIS).
Work on this question by the Technical Committee began in 1957 and led, in 1959, to the
adoption of a Draft IS0 Recommendation.
In May 1960, this Draft IS0 Recommendation (No. 362) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature,
by the following Member Bodies :
Argentina France New Zealand
Germany Norway
Australia
Austria Greece Poland
Canada Hung a r y Spain
Chile India Switzerland
Israel United Kingdom
Colombia
Czechoslovakia Italy U.S.A.
Denmark Japan
Finland Netherlands
Three Member Bodies opposed the approval of the Draft:
Bulgaria Sweden U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in July 1962, to accept it as an IS0 RECOMMENDATION.
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FOREWORD
This IS0 Recommendation is one of a number of IS0 Recommendations determining inter-
nationally interchangeable triangular screw threads.
It is intended that the complete set of these IS0 Recommendations will cover the following speci-
fications :
Basic Profile for IS0 Triangular Screw Threads
(except for pipe threads)
and design profiles for nut and bolt (IS0 Recommendation R 68, section 2)
IS0 Metric Screw Threads. General Plan
(diameter range 0.25 to 300 mm) (IS0 Recommendation R 261)
IS0 Metric Screw Threads for screws, bolts and nuts
(IS0 Recommendation R 68, section 3)
(a) diameter range 0.25 to 5 mm
(b) diameter range 6 to 39 mm (IS0 Recommendation R 262)
IS0 Inch Screw Threads. General Plan
(diameter range 0.06 to 6 in)
and selection for screws, bolts and nuts (IS0 Recommendation R 263)
IS0 Selected Screw Threads for screws, bolts and nuts (Under study)
All these IS0 Recommendations on screw threads will utilize the Basic Profile for IS0 Trian-
gular Screw Threads set out in IS0 Recommendation R 68, Screw Threads.
CONTENTS
Page
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1. Introduction . 4
2. Thread series . 4
3. Designations . 4
4. Screw Threads (Table 1) . 5-6
Appendix . 7
Al. Usage of thread series. . 7
8
A2. Corresponding inch-millimetre values .
8
(a) Basic major diameters (Table 2). .
(b) Pitches (Table 3). . 8
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ISOlR 263 - 1962 (E)
IS0 Recommendation July 1962
IS0 INCH SCREW THREADS
GENERAL PLAN AND SELECTION FOR SCREWS, BOLTS AND NUTS
(diameter range 0.06 to 6 in)
1. INTRODUCTION
This IS0 Recommendation tabulates IS0 Inch Screw Threads (except for pipe threads) having
the Basic Profile for IS0 Triangular Screw Threads.
It comprises both a General Plan of the IS0 Inch Screw Threads and the IS0 Inch Screw Threads
for screws, bolts and nuts, the latter being a selection from the former.
The IS0 Recommendation contains sizes in the diameter range 0.06 to 6 in, comprising a number
of series of diameter-pitch combinations, together with a system of thread designations.
It remains for each industry to choose for itself, by means of selection among the screw threads
of this IS0 Recommendation, the diameter-pitch combinations appropriate to its own needs.
2.THREAD SERIES
The General Plan is characterized by a number of thread series, i. e. groups of diameter-pitch
combinations distinguished from each other by the number of threads per inch associated with
specific diameters of threads. These thread series are shown in Table 1.
2.1 Diameters
Columns 1 and 2 of Table 1 give primary and secondary sizes which should suffice to meet the
common needs of design. Column 3 gives the decimal equivalents of these sizes
2.2 Number of threads per inch
Columns 4 to 14 (inclusive) of Table 1 give the number of threads per inch which are recom-
mended for association with the sizes in columns 1 and 2. These columns of threads per inch
are divided into two groups :
Series with graded pitches
: columns 4, 5 and 6,
Series with constant (uniform) pitches: columns 7 to 14.
2.2.1. Series with graded pitches
There are three series with graded pitches. They are headed “coarse”, “fine” and “extra-
fine”, in compliance with present practice.
These terms denote tht! relative magnitudes of the pitches of the three series for any
given diameter of thread and do not imply any difference in the quality of the threads
in the series.
The coarse and fine thread series should be the ht choice for general engineering appii-
cations, and they form the selected series for the commercial production of screws, bolts
and nuts.
2.2.2. Series with constant (unvorm) pitches
In addition to the three series of graded pitches, Table 1 includes columns of constant
pitches which have been selected from the range 4 to 32 threads per inch. Each of these
series is limited to an appropriate range of diameters.
3. DESIGNATIONS
The screw threads in this General Plan are designated as shown in the column headings of Table 1,
i. e. as follows:
3.1 Series with graded pitches
Coarse thread series Designation UNC; e. g. i/4-20 UNC; No. 4-40 UNC;
Fine thread series Designation UNF; e. g. i/4-28 UNF; No. 4-48 UNF;
Extra-fine thread series Designation UNEF; e. g. i/4-32 UNEF.
3.2 Series with constant (dom) pitches
Ail of the diameter-pitch combinations of the threads in these constant-pitch series are desig-
nated UN; e. g. 1-16 UN.
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ISOlR 283 - 1962 (E)
4. SCREW THREADS
TABLE 1.
Number of thread8 per inch
Series with
Series with constant (uniform) pitches
Sizes
Major MC I graded pitches
-- -
Extra- &thread 6-thread 8-thread 16-
12- 20- 28- 32-
fine series series series thread thread thread thread thread
thread
series senes series series series
series
Secon-
UNEF UN UN UN
UN UN UN UN UN
dary
~
2
10 11
...