How to measure wire rope diameter

he correct diameter of a wire You should make rope is the diameter of a circum- the T scribed circle that will enclose carefully with all the strands. It’s the largest cross- calipers. The sectional measurement as shown here. illustrations

Metric conversion and equivalents

s we move toward metric measure- A ments, it will become increasingly Nominal wire rope diameter True diameter necessary to convert into Inches Millimeters Inches Millimeters SI – International System of Units – (or metrics), and vice versa. The following 1/4 6.5 2 1/8 54 table and conversion factors are included 5/16 8 2 1/4 58 in this handbook to help you. 3/8 9.5 2 3/8 60 7/16 11.5 2 1/2 64 Rope diameter 1/2 13 2 5/8 67 In measuring rope diameter, the industry 9/16 14.5 2 3/4 71 is leaning toward a “soft” conversion to metric during the transition period. For 5/8 16 2 7/8 74 example, a 1” diameter rope converts 3/4 19 3 77 to 25.4 mm in metrics. Using the soft 7/8 22 3 1/8 80 Correct conversion, this is changed to the whole 1 26 3 1/4 83 metric size that most nearly parallels the 1 1/8 29 3 3/8 87 1” size range, or 26 mm. In sizes smaller 1 1/4 32 3 1/2 90 than 5/8”, the rope diameter is rounded

to the nearest 0.5 mm. 1 3/8 35 3 3/4 96 1 1/2 38 4 103 Strengths and weights 1 5/8 42 4 1/4 109 The following table gives the closest Incorrect equivalent metric diameters for rope 1 3/4 45 4 1/2 115 sizes up through 5 inches. Again, these 1 7/8 48 4 3/4 122 metric sizes are based on the industry’s 2 52 5 128 “soft” conversion.

Since rope minimum breaking force and weight per vary for different > To convert rope minimum breaking types and grade of ropes, the following force in tons (T) to kilograms (kg), conversion factors are given to help you multiply by 907.2. convert the figures you need: Note: The newton (a unit of force) is the > To convert rope weight in pounds per correct unit for measurement of minimum (lb/ft) to kilograms per meter breaking force in the SI system of units. (kg/m), multiply by 1.488. We have included a conversion factor from tons to kilograms because a rope’s > To convert rope minimum breaking minimum breaking force is often referred force in tons (T) to kilonewtons (kN), to in terms of kilograms (a unit of mass). multiply by 8.897; 1 lb equals 4.448 newtons (N).

10 Union A WireCo WorldGroup Brand at left show the correct and incorrect methods of measuring a wire rope’s Nominal rope tolerance diameter Under Over diameter. 0 - 1/8” - 0 + 8% Allowable tolerance Over 1/8 - 3/16” - 0 + 7% in wire rope diameter Over 3/16 - 5/16” - 0 + 6% Wire rope is normally made slightly Over 5/16” - 0 + 5% larger than its catalog (or nominal) size. The following chart lists the size tolerances of standard wire rope.

Design factors

he design factor is defined as the types on the same application may have Tratio of the minimum breaking different design factor requirements. force of a wire rope to the total load it is expected to carry. How to use design factors Standards and regulations require that Use of design factors provides rope design factors be applied to the rope’s installations with reasonable assurance minimum breaking force to determine of adequate capacity for the work to be the maximum working load. To deter- done throughout a rope’s service life. mine the maximum working load for Considerations in establishing design which an operating rope may be used, factors include the type of service, divide the rope’s minimum breaking design of equipment and consequences force by the required design factor. This *Note of failure. is the rope’s maximum working load. There may be other limiting factors in > The rated capacity In most applications, the selection of a an application that make the maximum of a wire rope sling rope based on the proper design factor load the equipment can handle less than incorporates both has been made by the equipment the rope’s maximum working load.* a design factor manufacturer. In an application where and a splicing or a different rope is to be used, or in a Remember, an installation is only at attachment efficiency. new application, check government the prescribed design factor when the and industry regulations for the rope is new. As a rope is used, it loses required design factor. Different rope strength and literally is “used up.”

Union A WireCo WorldGroup Brand 11