ISO 11891:2012

Overview

ISO 11891:2012 - Hot formed helical compression springs - Technical specifications defines engineering and quality requirements for hot formed helical compression springs made from quenched-and‑tempered hot‑coiled round steel bar. The standard covers materials, geometry, manufacturing, tolerances and test methods for common compression springs within defined size and performance limits. It is not intended for heavy-duty special‑performance coil springs (for example, railway or automotive suspensions).

Key limits specified

• Free length ≤ 900 mm
• Wire diameter 8 mm to 60 mm
• Mean coil diameter ≤ 460 mm
• Spring index 3 to 12
• Slenderness ratio 0.8 to 4
• Active coils ≥ 3
• Spring pitch < 0.5 D

Key topics and technical requirements

• Materials and bar tolerances: Default material per ISO 683‑14; hot‑rolled and cold‑worked bar diameter tolerances referenced (ISO 1035‑4 and tables in ISO 11891).
• Spring construction: Helix direction, common coil‑end types (closed/ open, ground, tapered) and guidance for nested springs.
• Geometry & characteristics: Free length, solid length, coil diameters, total coils, pitch and limits on irregularity so coils do not contact when compressed to 80% of total deflection.
• Spring rate & measurement: Spring rate is defined as force per unit deflection; rate calculation uses load points at 30–70% of total deflection. Specified lengths/loads should correspond to 20–80% of nominal deflection.
• Tolerances: Three tolerance grades (Grade 1–3) for dimensions (free length, diameter, coils), perpendicularity and parallelism, plus explicit numeric tables for limits.
• Manufacturing requirements & tests: Heat treatment, hardness, decarburization, grain size (ISO 643), surface condition, end machining, shot peening, setting/presetting and surface protection. Test methods are defined for all key properties (sections 9.x).

Applications and users

ISO 11891 is practical for:

• Spring manufacturers producing hot‑formed compression springs for industrial machinery, valves, pressure vessels, actuators and heavy equipment components.
• Design engineers specifying springs for assemblies where hot‑formed steel springs are appropriate.
• Quality and inspection teams verifying tolerances, heat treatment and surface treatments.
• Procurement and contract teams referencing standard requirements in purchase orders.

Keywords: ISO 11891, hot formed helical compression springs, spring tolerances, spring materials, manufacturing requirements, test methods, spring rate.

Related standards

• ISO 683‑14 (steel material grades)
• ISO 26909 (spring vocabulary)
• ISO 643 (grain size)
• ISO 1035‑4 (bar tolerances)
• ISO 7500‑1, ISO 18265 and ISO 80000‑1 (referenced measurement/calculation standards)