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IS0
I N T E R NAT1 O N AL O R GAN I Z AT1 O N F O R S TAN DAR DI ZAT I O N
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IS0 RECOMMENDATION
R 296
SELF-HOLDING TAPERS FOR TOOL SHANKS
1st EDITION
March 1963
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 296, Serf-holding Tapers for Tool Shanks, was drawn up by
Technical Committee ISO/TC 39, Machine Tools, the Secretariat of which is held by the
Association Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1950, taking into account the
studies which had been made by the former International Federation of the National Standard-
izing Associations (ISA), and led, in 1955, to the adoption of a Draft IS0 Recommendation.
In July 1960, this Draft IS0 Recommendation (No. 388) 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 Hungary Portugal
Belgium
India Romania
Chile Israel Spain
Colombia Italy Sweden
Czechoslovakia Japan Switzerland
Denmark Netherlands United Kingdom
France New Zealand U.S.A.
Germany Poland U.S.S.R.
One Member Body opposed the approval of the Draft:
Australia.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Coun-
cil, which decided, in March 1963, to accept it as an IS0 RECOMMENDATION.
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ISOIR 296 - 1963 (E) W
IS0 Recommendation R 296 March 1963
SELF-HOLDING TAPERS FOR TOOL SHANKS
1. INTRODUCTION
Tapers for tool shanks with a small taper of about 4 to 5 per cent may be classified into three
categories according to their use :
(1) tapers for general use,
(2) smaller tapers,
(3) larger tapers.
For the first category, tapers recommended by IS0 are No. 1 to 6 Morse tapers. Their standard
sizes in millimetres are given in Table 1, pages 5-6, and the corresponding sizes in inches are
given in Table 2, pages 7-8.
For smaller and larger tapers, those recommended by IS0 are, on the one hand, No. 4 and 6 me-
tric 5 per cent tapers and No. O Morse taper, on the other hand, No. 80 to 200 metric 5 per
cent tapers. Their sizes, in millimetres only, are given for the Morse taper in Table 1, pages
5-6, and for the metric tapers, in Table 2, pages 7-8.
However, it was agreed to include, in the category of small tapers No. 1 to 3 Brown & Sharpe
tapers in parallel. Their sizes, in inches only, are given in Table 2, pages 7-8.
Consequently, as shown in the table below, self-holding tapers dealt with in this IS0 Recommend-
ation include :
(1) for general use, only No. 1 to 6 Morse tapers;
(2) for sizes above No. 6 Morse taper, only No. 80 to 200 metric tapers (without corresponding
tapers in the inch tables);
(3) for sizes below No. 1 Morse taper, two solutions: either, No. 4 and 6 metric tapers and No. O
Morse taper (without corresponding tapers in the inch Table 2) or, alternatively, No. 1
to 3 Brown & Sharpe tapers (without corresponding tapers in the metric Table 1).
No. 4 and 6 metric and
Small tapers No. 1 to 3 Brown & Sharpe
1
I 1 No. O Morse I
Lastly, this IS0 Recommendation provides, for those elements which are threaded, two entirely
distinct types of products, according to the type of thread, M or UNC.
In order to distinguish between these two types, it is important that the element itself be marked
with the corresponding thread symbol, each national standards body being free to adopt, in its
national standard, either of the two threads.
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ISOlR 296 - 1963 (E)
2. INTERCHANGEABILITY
2.1 Due to the fact that each national standards body is left free to adopt in its national standard,
for small tapers below No. 1 Morse taper, either the solution “Metric tapers and No. O Morse
taper” or the alternative “Brown & Sharpe”, in this limited field of small tapers interchange-
ability will be possible only between countries that have adopted the same one of those two
solutions.
2.2 Due to the fact that each national standards body is also left free to adopt in its national
standard, for external tapers with tapped holes, either the M thread or the UNC thread,
interchangeability will be possible, with this type of external taper, only between countries
that have adopted the same one of those two types of thread.
2.3 On the other hand, for all sizes other than for threads, the No. 1 to 6 Morse tapers, manu-
factured either to metric values or to inch values, are strictly interchangeable, though not
absolutely identical. Acceptance conditions, if provided for in national standards, should
therefore be such that they should allow the acceptance of either the tapers specified in metric
units or the tapers specified in inch units.
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I I
lSOlR 296 - 1963
4. SIZES M INCHES*
* For sizes of No. O Morse taper and 5 per cent metric tapers, see Table 1.
1516
: 12 0.631 51 : 12 0.625 65 : 12
254 ~ = 1:19.002 1 = 1:19.180
94 , = 0.05263 = 0.052 14
- (l) Di and d or dz - approximate values given for guidance.
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