ACTUAL DIAMETER
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U
A
The actual rope diameter is the diameter
of
the circumscribing firc1e, i.e., its
largest cross-sectional dimension.
To
insure accuracy this measurement should be
made with a wire rope caliper using the
correct method (b) shown in Fig. 17.
Special techniques and equipment must be employed for measuring ropes with an
odd number
of
outer strands (e.g. Circumferential tapes, calipers and plates).
Tolerance for wire rope diameter pennit the diameter to be slightly larger than the
nominal size, according to the limits shown
in Table 3.
TABLE 3
OVERSIZE
LIMITS
OF
WIRE
ROPE
DIAMETERS*
Nominal Rope Diameter
Allowable Limits
Thru
1/8" (3.2 mm)
-0
Over 1/8" (3.2 mm) thm 3/16" (4.S mm)
-0
Over 3/16" (4.Smm) thm
5/16"
(8.0 mm)
-0
Over 5/16" (S.omm) and larger -0
* These limits have been adopted
by
the Wire Rope Technical
Board (WRTB). In the case
of
certain special purpose ropes,
such
as
aircraft cables and elevator ropes, each has specific
requirements.
If a question should arise regarding compliance
with oversize tolerances the rope may be measured under
tension not exceeding
20%
of
the minimum breaking force.
If
the actual
diameter determined by this measurement is within the specified
tolerance the rope is considered to meet the required diameter.
+8%
+7%
+6%
+5%
C.
INCORRECT
Figure 17. How to measure (or caliper) a wire rope correctly. Since the "true" diameter (A) lies
within the circumscribed circle, always measure the larger dimension (B).
26 • Wire Rope Technical Board - Wire Rope Users Manual, Fourth Edition
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