Overview
EN ISO 16047:2005 - Fasteners: Torque/clamp force testing (ISO 16047:2005) defines conditions and procedures for measuring the tightening behaviour of threaded fasteners. The standard covers bolts, screws, studs and nuts (carbon and alloy steel) with ISO metric threads M3 to M39, referencing mechanical property standards ISO 898‑1, ISO 898‑2 and ISO 898‑6. It establishes how to determine relationships between applied tightening torque and resulting clamp force, and how to measure related parameters such as torque coefficients and friction.
Key topics and requirements
- Scope and exclusions
- Applicable to ISO metric threaded fasteners and compatible internal/external threads to ISO 68‑1.
- Not applicable to set screws, thread-forming screws or fasteners with additional self‑locking features.
- Measured characteristics
- Torque coefficient (K‑factor) and ratio T/F (torque to clamp force).
- Coefficients of friction: total (µ_tot), thread friction (µ_th) and bearing‑surface friction (µ_b).
- Yield and ultimate clamp force (F_y, F_u) and corresponding tightening torques (T_y, T_u).
- Rotation angle during tightening.
- Test conditions
- Tests normally at room temperature; standard testing range 10 °C to 35 °C (unless otherwise agreed).
- Two test modes: standard conditions (using specified test‑bearing plates, washers, test nuts/bolts) and specific conditions (custom fixtures, coatings, lubrication, temperatures).
- Apparatus and test parts
- Requires controlled testing machine, test fixture, standard test‑bearing plates or washers, and appropriately specified test nuts/bolts.
- Evaluation and reporting
- Defines calculations and reporting requirements for torque/clamp force relationships and friction coefficients, plus full test‑report content.
Practical applications and users
- Who uses EN ISO 16047:2005
- Fastener and component manufacturers, test laboratories, OEM assembly engineers, quality assurance and R&D teams in automotive, aerospace, heavy machinery and construction.
- Why it’s used
- To validate assembly torque specifications and K‑factors used in joint design.
- To evaluate effects of coatings, lubricants and surface finishes on tightening behaviour.
- For quality control, material qualification, failure analysis and setting production torque tools.
- Benefits
- Provides repeatable, comparable torque‑tension data for safer and more reliable bolted joints and optimized assembly processes.
Related standards
Keywords: EN ISO 16047:2005, torque/clamp force testing, fastener testing, torque coefficient, clamp force, K‑factor, thread friction, M3–M39.
