ISO 7042:2025

Overview - ISO 7042:2025 (Prevailing torque hexagon high nuts)

ISO 7042:2025 specifies the characteristics of prevailing torque (all metal) hexagon high nuts for metric coarse pitch threads M5 to M39, in steel and stainless steel, with product grades A and B. The standard defines dimensions, material and mechanical requirements, marking and labelling, and designation rules for high nuts that include an all‑metal prevailing torque feature (no polymer inserts).

Key topics and technical requirements

• Thread range and materials: Metric coarse pitch threads M5–M39; allowable materials include carbon/alloy steel and stainless steel (select grades and property classes from ISO 898‑2 and ISO 3506‑2).
• Product grades: Product A (typically D ≤ M16) and B (D > M16) as specified in the standard.
• Dimensional rules: Overall nut height is based on the high‑nut style (hmin = mmin per ISO 898‑2 / ISO 4033 style 2) with hmax established as a function of hmin (tolerance (hmax − hmin) does not follow the ISO IT tolerance system). Detailed dimensions are provided in the standard’s tables and figure.
• Thread tolerances: Default thread tolerance class 6H; 6G may be specified for coated nuts where applicable.
• Functional/quality requirements: Functional properties reference ISO 2320 for prevailing torque steel nuts; for stainless steel, functional test methods may require national standards (e.g., NF E 25‑035‑2) or purchaser/supplier agreement.
• Surface, coatings and finish: As‑processed, clean/bright, electroplated (ISO 4042), zinc‑flake (ISO 10683) and other finishes are addressed; acceptance and surface discontinuity limits reference ISO 6157‑2 and ISO 3269.
• Marking and labelling: Product marking follows ISO 898‑2 (steel) or ISO 3506‑2 (stainless); package labelling must include ISO 7042 reference, thread size, property class/grade, surface condition, manufacturer ID, lot number and quantity.

Applications and who uses ISO 7042

• Used by fastener manufacturers, mechanical design and fastening engineers, procurement/specification writers, quality inspectors and suppliers who require standardization of prevailing torque hexagon high nuts.
• Typical use cases: applications needing reliable self‑locking metal hexagon high nuts where polymer inserts are unsuitable (high temperature, chemical exposure, longevity requirements).
• Beneficial for industries and projects that demand interchangeability, traceability and verified functional performance of locking nuts.

Related standards

• ISO 898‑2 (mechanical properties of nuts), ISO 3506‑2 (stainless steel nuts), ISO 2320 (prevailing torque steel nuts), ISO 965‑1 (thread tolerances), ISO 4759‑1 (tolerances/product grades), ISO 3269 (acceptance inspection), ISO 4033 (hexagon high nuts style 2).

Keywords: ISO 7042, prevailing torque hexagon nuts, high nuts (all metal), metric M5–M39, fasteners, ISO 898‑2, ISO 3506‑2.