Proof load of steel nuts, fine thread
Steel nuts (coarse thread)ISO 898-2 (JIS B 1052-2)Unlike bolts, the proof stress rises with nominal diameter within the same property class. Steel nuts (fine thread)ISO 898-6 (JIS B 1052-6)A separate standard from the coarse thread. At the same property class the stress is higher, and the range of nominal diameters is narrower.Stainless steel nuts (coarse thread)ISO 3506-2 (JIS B 1054-2)The proof stress does not change with the nominal diameter; it splits into two according to the nut height.Stainless steel nuts (fine thread)ISO 3506-2 (JIS B 1054-2)The proof stress is the same as for the coarse thread. The larger stress area makes the proof load larger by the same amount.
Notes
- The proof load is the effective sectional area multiplied by the proof stress. The effective sectional area is calculated as given in JIS B 1082. Checked against the table in the source (JIS B 1052-6:2009, Table 6).
- Fine thread nuts are covered by a separate standard (JIS B 1052-6), with a different range of sizes. Nominal diameters start at 8 mm, and There is no property class 9. Only the 19 designations covered by the source appear in the table, three more than the bolt standard (JIS B 1051) covers (
M18×2,M20×2andM22×2). A blank means that that property class is not specified for that size (classes 10 and 12 apply only up to 16 mm). - For the same property class the proof stress is higher than for coarse thread. For class 8 it is 955 to 1090 N/mm2, against 855 to 920 N/mm2 for coarse thread. A fine thread is weaker, so more is asked of the nut.
- The values here are for room temperature. Mechanical properties change at high and low temperatures, so do not apply these values directly.
- Sources: JIS B 1052-6, JIS B 0205-4, JIS B 1082