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1/8 Inch Wire Rope Breaking Strength and SWL
A 1/8" wire rope is 3.2 mm nominal. At that size our minimum breaking load runs from 5 kN to 9.26 kN depending on construction and grade - 7x19 1570 MPa at 5 kN, against 1x19 1960 MPa at 9.26 kN. At a 5:1 safety factor the working load is 1 kN to 1.9 kN.
Breaking strength of a 1/8" 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 | 3 mm | 1570 MPa: 5 kN / 509 kg | 0.03 / 0.02 |
| 1x19 | 3 mm | 1770 MPa: 8.36 kN / 853 kg 1960 MPa: 9.26 kN / 944 kg | 0.05 / 0.03 |
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 | 3 mm | 1570 MPa | 5 | 1 | 0.8 | 0.6 |
| 1x19 | 3 mm | 1770 MPa | 8.36 | 1.7 | 1.4 | 1 |
| 1x19 | 3 mm | 1960 MPa | 9.26 | 1.9 | 1.5 | 1.2 |
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.
1/8" on the order
At 3 mm this is the smallest diameter in the range, and the only one where 7x19 is the default rather than the alternative: a rope this thin has to run round small sheaves and thimbles, and the flexible 7x19 does that where the stiff 1x19 does not. The cost is strength - 5 kN against 8.36 kN at the same diameter, so choose the construction against the duty, not the size alone.
The inch size is nominal and the stock diameter is what ships, so both belong on the enquiry - “1/8" (3 mm) 1x19, 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:
3/16" · 1/4" · 5/16" · 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.