Nomenclature, Threads - prime mover smx45 Master Service Manual

F-code Section
PT M1.1
Inch (SAE) and Metric Fasteners
Version no T-code
001 SMX
40
Return
C-code

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 shank of 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 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
1/2 x 13 UNC x 1-1/2
A B
A =Shank diameter
B =Number of threads per unit of length
C =Type of thread
D =Shank length
Master Service Manual
C D
Metric
M12 x 1.75 x 50
A B C
A =Thread size
B =Pitch
C =Length
2004-01-12