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The company reserves the right to vary models and dimensions without notice.
These products are designed for industrial applications and are not suitable for sale to the general public.
TECHNICAL DATA
Technical Data
10
NORTH AMERICAN FITTINGS & FLOW CONTROL VALVE CATALOG
>
Release 8.6
Preferred sizes
International standard ISO 261 defines a detailed list of preferred combinations of outer diameter D and pitch P for
ISO metric screw threads. ISO 262 defines the following shorter list of thread dimensions – a subset of the combi-
nations listed in ISO 261 – which are selected sizes for screws, bolts and nuts:
Nominal Diameter (D/
mm)
Pitch (P/mm)
Nominal Diameter
(D/mm)
Pitch (P/mm)
1st Choice 2nd Choice Coarse
Fine
1st Choice 2nd Choice Coarse
Fine
1
0.25
16
2
1.5
1.2
0.25
18
2.5
2
1.5
1.4
0.3
20
2.5
2
1.5
1.6
0.35
22
2.5
2
1.5
1.8
0.35
24
3
2
2
0.4
27
3
2
2.5
0.45
30
3.5
2
3
0.5
33
3.5
2
3.5
0.6
36
4
3
4
0.7
39
4
3
5
0.8
42
4.5
3
6
1
45
4.5
3
7
1
48
5
3
8
1.25
1
52
5
4
10
1.5
1.25 1
56
5.5
4
12
1.75
1.5 1.25
60
5.5
4
14
2
1.5
64
6
4
The ISO metric screw threads are the worldwide most commonly used type of general-purpose screw thread. They
were one of the first international standards agreed when the International Organization for Standardization was set
ISO Metric Screw Thread
References
International standards:
• ISO 68-1: ISO general-purpose screw threads — Basic profile — Metric screw threads.
• ISO 261: ISO general-purpose metric screw threads — General plan.
• ISO 262: ISO general-purpose metric screw threads — Selected sizes for screws, bolts
and nuts.
• ISO 965-1: ISO general-purpose metric screw threads — Tolerances — Part 1:
Principles and basic data.
Equivalent national standards:
• BS 3643: ISO metric screw threads
• ANSI/ASME B1.13M: Metric Screw Threads: M Profile
The “coarse“ pitch is
the commonly used
default pitch for a
given diameter. In
addition, one or two
smaller “fine“ pitches
are defined, for use in
applications where the
height of the normal
“coarse“ pitch would
be unsuitable (e.g.,
threads in thin-walled
pipes). The terms
“coarse” and “fine“
have in this context no
relation to the manu-
facturing quality of the
thread.
up in 1947.
Designation
A metric ISO screw thread is designated
by the letter M followed by the value of the
nominal diameter D (Dmaj in the diagram
above) and the pitch P, both expressed in
millimeters and separated by
the multiplication sign “×”.
Example:
M8×1.25
If the pitch is the normally used
“coarse” pitch listed in ISO 261
or ISO 262, it is omitted.
Example:
M8 Tolerance classes
defined in ISO 965-1 can be
appended to these designations,
if required.
Example:
M10 – 6g in external
threads.