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5/16 Inch Wire Rope Breaking Strength and SWL
A 5/16" wire rope is 7.9 mm nominal. At that size our minimum breaking load runs from 35.6 kN to 65.9 kN depending on construction and grade - 7x19 1570 MPa at 35.6 kN, against 1x19 1960 MPa at 65.9 kN. At a 5:1 safety factor the working load is 7.1 kN to 13.2 kN.
Breaking strength of a 5/16" wire rope by construction
Each row is a construction we stock at this size, with the stock diameter matching the inch size and the minimum breaking load published on that product table. Where a construction is made in both grades, both are given.
| Construction | Stock diameter | Minimum breaking load (kN / kg) | Weight (kg/m / lb/ft) |
|---|---|---|---|
| 7x19 | 8 mm | 1570 MPa: 35.6 kN / 3,630 kg | 0.24 / 0.16 |
| 6x36 IWRC | 8 mm | 1770 MPa: 40.3 kN / 4,113 kg 1960 MPa: 44.7 kN / 4,555 kg | 0.26 / 0.17 |
| 1x19 | 8 mm | 1770 MPa: 59.5 kN / 6,062 kg 1960 MPa: 65.9 kN / 6,713 kg | 0.32 / 0.22 |
MBL is the minimum breaking load - the load at which the rope is required to break. It is never a working load. The kg figure is the product table’s own kilogram column (1 kN = 101.97 kg).
Working load at 5:1, 6:1 and 8:1
Working load is the breaking load divided by a safety factor. The factor comes from the application and the standard that governs it - lifting gear is treated differently from a static guy. The columns below are arithmetic on the published MBL, not a recommendation for any particular duty.
| Construction | Stock diameter | Grade | MBL (kN) | 5:1 working load (kN) | 6:1 working load (kN) | 8:1 working load (kN) |
|---|---|---|---|---|---|---|
| 7x19 | 8 mm | 1570 MPa | 35.6 | 7.1 | 5.9 | 4.5 |
| 6x36 IWRC | 8 mm | 1770 MPa | 40.3 | 8.1 | 6.7 | 5 |
| 6x36 IWRC | 8 mm | 1960 MPa | 44.7 | 8.9 | 7.5 | 5.6 |
| 1x19 | 8 mm | 1770 MPa | 59.5 | 11.9 | 9.9 | 7.4 |
| 1x19 | 8 mm | 1960 MPa | 65.9 | 13.2 | 11 | 8.2 |
Conversion: 1 kN = 101.97 kg = 0.102 tonnes. The highest breaking load in the table above, divided by 5, is the figure in the first column of this one.
5/16" on the order
0.3125 in is 7.94 mm, and 8 mm is the first diameter where 6x36 IWRC exists - below it, only the two small constructions are made. Three options now run in parallel at the same nominal size: 35.6 kN, 40.3 kN and 59.5 kN. The 6x36 is the usual compromise, flexible enough to run over sheaves and stronger than 7x19 at the same diameter.
The inch size is nominal and the stock diameter is what ships, so both belong on the enquiry - “5/16" (8 mm) 6x36 IWRC, 1770 MPa” - together with the length, the end fittings and the duty. That lets the quotation answer the installation rather than the size alone.
Other wire rope sizes
Every size in the range has its own page, built from the same product tables:
1/8" · 3/16" · 1/4" · 3/8" · 1/2" · 5/8" · 1" · breaking strength chart
For where these figures come from see the wire rope breaking strength chart, the construction guide and the core types guide; for everything stocked at this size, the wire rope range.