M1.1
001
Version no T-code
F-code Section C-code
Inch (SAE) and Metric Fasteners
24
Service Manual 1997-09-24
2. Nomenclature, Threads
The thread design is specified by a series of numbers and
letters for inch and metric fasteners (see figure below). The
diameter of the shank of the fastener is shown first in the
series, e.g. M12=12 mm, M20=20 mm (1/2=1/2 inch, 3/4=3/4
inch).
The number of threads per inch is normally not shown for inch
nomenclature and only the UNC (Unified National Coarse) or
UNF (Unified National Fine) is shown. This number of threads
per inch is not shown because a UNC or UNF fastener has a
standard number of threads per inch for a specific diameter.
The length of a shank is often indicated as part of the
description of a fastener. This length is shown in inches for
inch fasteners and in millimeters for metric fasteners.
A cap screw will have the following description:
INCH METRIC
1/2 x 13 UNC x 1-1/2
A B C D
M12 x 1.75 x 50
A B C
A = SHANK DIAMETER
B = NUMBER OF THREADS PER UNIT
OF LENGTH
C = TYPE OF THREAD
D = SHANK LENGTH
A = THREAD SIZE
B = PITCH
C = LENGTH
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