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üDC 621.882.082.1 (100)
IS0
I N T E RN AT I O N A L O R G A N I Z AT I O N FOR STAND AR D 1 ZAT I O N
IS0 RECOMMENDATION
R 261
IS0 GENERAL PURPOSE METRIC SCREW THREADS
GENERAL PLAN
2nd EDITION
r' September 1969
This second edition supersedes the first edition.
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 261, IS0 metric screw threads - General pbn (diameter range 0.25 to 300 mm), was drawn
up by Technical Committee ISO/TC 1, Screw threads, the Secretariat of which is held by the Svenges Standardiseringskommission (SIS).
Work on this question led to the adoption of a Dràft IS0 Recommendation.
In May 1960, this Draft IS0 Recommendation (No. 297) was circulated to all the IS0 Member Bodies for enquiry. It was
approved by 30 Member Bodies. One Member Body opposed the approval of the Draft.
This Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided, in July 1962,
to accept it as an IS0 RECOMMENDATION.
L
BRIEF HISTORY RELATING TO THE 2nd EDITION
In 1967, Technical Committee ISO/TC 1 decided to revise the IS0 Recommendation R 261-1962, deleting
the sizes below 1 mm, and a Draft IS0 Recommendation was adopted to this effect.
In May 1968, this Draft IS0 Recommendation (No. 1499) 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 :
Austria Israel South Africa, Rep. of
Belgium Italy Spain
Canada Japan Sweden
Chile Korea, Rep. of Switzerland
Czechoslovakia Net herlands Thailand
Cuba New Zealand Turkey
Denmark Norway U.A.R.
France r' Peru United Kingdom
Germany Poland U. S.S. R.
Hungary Portugal
India Romania
Two Member Bodies opposed the approval of the Draft :
Australia
U.S.A.
This Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided,
in September 1969, to accept it as a revision of IS0 Recommendation R 261-1962, the title of which is modified
as follows ; IS0 general purpose metric screw threads - General plan.
This edition (2nd edition) cancels and replaces the first edition of IS0 Recommendation R 261-1962.
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-4- ISO/R 261-1969 (E)
FOREWORD
Thi
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