General; Threaded Fasteners; Nomenclature, Threads - Yale 524150797 Maintenance Manual

8000 YRM 0231

THREADED FASTENERS

Threaded fasteners, like bolts, nuts, capscrews, and
studs, are made to specifications that describe the
mechanical strength and hardness of the fastener. A
fastener used in a design application is selected
according to its specifications. Yale
parts from many countries. Parts that are purchased
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must be to Yale Company standards. There are
several standards used by these countries in the
manufacture of threaded fasteners. Many of these
fasteners are similar, but cannot be used as a direct
replacement. To make sure that you have the correct
fastener, order fasteners and parts through the Yale
Parts Depot.
Service persons must use replacement fasteners that
have the same specifications. Fasteners made to each
specification have identification marks for that
specification. This specification is commonly called
"Grade" for SAE standards and "property class" for
metric standards. This section describes the
identification of some common fasteners.
The metric system used by Yale
described as SI (Le Systeme d'Unites or the
International System of units, also called SI in all
languages). The SI System of measurement is
described in ISO Standard 1000, 1973. A conversion
table of common measurements is shown in Table 7.

NOMENCLATURE, THREADS

The thread design is specified by a series of numbers
and letters for inch and metric fasteners. See Figure 1.

General

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The diameter of the shank of the fastener is shown
first in the series [M12 = 12 mm, M20 = 20 mm (1/2 =
1/2 in., 3/4 = 3/4 in.)].
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.
Metric fasteners show the number of threads per
millimeter.
The length of the 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 capscrew will have the following description:
Metric
M12 × 1.75 × 50
A B C
A = Thread Size
B = Pitch
C = Length
General
Inch
1/2 × 13 UNC × 1-1/2
A B C D
A = Shank Diameter
B = Number of Threads Per
Unit of Length
C = type of Thread
D = Shank Length
1