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CDU 621.9
IS0
O R GAN I ZATI O N FOR S TA N DAR DI ZATl O N
I N T E R N AT1 O N AL
IS0 RECOMMENDATION
R 237
DIAMETERS OF SHANKS AND SIZES
OF DRIVING SQUARES
FOR ROTATING TOOLS WITH PARALLEL SHANKS
1st EDITION
December 1961
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 237, Diameters of Shanks and Sizes of Driving Squares for Ro-
tating Tools with Parallel Shanks, was drawn up by Technical Committee ISOiTC 29, Small 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 and led in, 1958, to the
adoption of a Draft IS0 Recommendation.
In September 1959, this Draft IS0 Recommendation (No. 303) 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 Hungary Portugal
Belgium India Romania
Burma Italy Sweden
Czechoslovakia Mexico Switzerland
France Net herland s United Kingdom
Germany Pakistan U. S. S. R.
Greece Poland
One Member Body opposed the approval of the Draft: U. S. A.
IS0 Recommendation was then submitted by correspondence to the IS0 Council,
The Draft
which decided, in December 1961, to accept it as an IS0 RECOMMENDATION.
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ISO/R 237 - 1961 (E)
IS0 Recommendation R 237 Decem ber 1961
DIAMETERS OF SHANKS AND SIZES
OF DRIVING SQUARES
FOR ROTATING TOOLS WITH PARALLEL SHANKS
INTRODUCTION
I. SCOPE
'
This IS0 Recommendation relates to shank diameters and driving squares for rotating tools with
parallel shanks, such as reamers, screwing taps, etc.
It comprises two groups of tables :
1. a Principal Series and
2. a Secondary Series,
and gives for each of them
(1) the dimensions in millimetres and
(2) the corresponding dimensions in inches.
In each of the two series, the dimensions of driving squares for a given shank diameter are shown.
The complete range of diameters is divided into a certain number of diameter steps, for each
of which the corresponding standard square is given
- either in the Principal Series,
- or in the Secondqy Series, for use in cases where a finer subdivision is absolutely necessary
in the small diameters.
In the metric tables, the values of the across flats a of the squares and the preferred diameters d
are scaled in accordance with the series of preferred numbers R 20; the limits of the diameter
steps are the intermediate values of the series of preferred numbers R 40.
In the inch tables, the values a and d are exact conversions of the corresponding metric values,
expressed to three decimal places for the squares and to four decimal places for the diameters.
In the Principal Series; the tables give not only the two limits for each diameter step, but in
addition, for each step, the value of the preferred diameter (see list below), which corresponds
to the theoretical optimum ratio a/d = 0.80 between the across flats of the square and the dia-
meter of the shank.
Within any given step, this ratio ald varies between the extreme limits 0.75 and 0.85 for the
Principal Series, and 0.80 and 0.85 for the Secondary Series, taking account of the nominal values
of a and d only. If the tolerances on a and d are taken into account, it never falls below 0.72,
~
even in the worst cases.
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ISO/R 237 - 1961 (E)
Preferred diameters
Inches
Millimetres
0.044 1 0.440 9
1.12 11.2
1
1.25 12.5 0.049 2 0.492
0.055 1 0.551 2
1.40 14.0
0.063 O 0.629 9
1.60 16.0
0.070 9 0.708 7
1.80 18.0
2.00 20.0 0.078 7 0.787 4
0.881 9
2.24 22.4 0.088 2
0.098 4 0.984 2
2.50 25.0
0.110 2 1.102 4
2.80 28.0
1.240 2
0.124 O
3.15 31.5
1.397 6
3.55 35.5 0.139 8
0.157 5 1.574 8
4.00 40.0
0.177 2 1.771 7
4.50 45.0
0.196 9 1.968 5
5.00 50.0
L
2.204 7
5.60 56.0 0.220 5
0.248 O 2.480 3
6.30 63.0
0.279 5 2.795 3
7.10 71.0
0.315 O 3.149 6
8.00 80.0
0.354 3 3.543 3
9.00 90.0
3.937 O
10.00 100.0 0.393 7
II. INTERCHANGEABILITY
The dimensions in millimetres and in inches have been determined in such a way as to ensure
that the squares corresponding to a given diameter step are identical, whether expressed in
millimetres or in inches.
Furthermore, the limits of the diameter steps correspond exactly, so that two diameters, whether
in millimetres or in inches, belonging to the same diameter range have the same driving square.
t
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ISO/R 237 - 1961 (E)
SHANK DIAMETERS AND DRIVING SQUARES
FOR ROTATING TOOLS WITH PARALLEL SHANKS
(alternative form for
small diameters)
1. PRINCIPAL SERIES
1.1 Dimensions in millimetres
Shank diameter I
Shank diameter.
Driving square Preferred Driving square
Preferred 1
d d
shank
diameter
di%% I
over 1 inci.
over 1 inci. a I z4
a I 14
1.06 1 1.18 0.90 I 1.12 10.60 1 11.80 9.00 12
-
-~ -
1.18 1.32 1.00 1 1.25 11.80 ~ 13.20- 10.00 1 13
- ~ --
~- ~ ~
1.32 1 1.50 1
1.12 1.40 13.20 15.00 11.20 i 14 14.00 I
-- ~ ~ --
1.50 -1 1.70- 1.25
1.60 15.00 17.00 12.50 ~ 16- 16.00
~~ -- - ~ ~ -- -~
~
4
1.40 1
1.80 17.00 19.00 14.00 18 18.00
~ ~ ~ - -- ~- ~
1.60 i
2.00 19.00 21.20 16.00 20 20.00
- -~ - -- -~
1.80 ~ 2.24
21.20
...