The “Volvo STD 5511-719 Screw fastening technology - Determination of friction characteristics of threaded fasteners - Test methods” standard, developed by Volvo, describes the test methods used to measure and evaluate the friction characteristics (coefficient of friction / torque-stress relationship) of threaded fasteners such as bolts, screws, and nuts. These characteristics are critical in automotive and heavy vehicle assembly because they directly affect:
This standard is part of the broader family of Volvo mechanical coupling/connection standards (5511 standard series).
This standard does not have an international or national equivalent. However, there are a number of national and international standards that cover this subject, such as DIN 946 and ISO 16047.
The Volvo STD 5511-719 standard specifies test methods and strategies and replaces the following standards: STD 5511.71, STD 5511.711, STD 5511.73, STD 7121.41, STD 7121.45, and STD 5511.72.
The equipment used in the tests consists of three main parts:
The accuracy of the complete unit should be such that the total measurement error is a maximum of plus/minus 5 percent. The test equipment should be able to apply tightening torque automatically or manually per nut, screw, or bolt without creating lateral forces per nut or screw. The tightening speed should be adjustable. The test equipment should be fitted with a device for measuring the total torque. The accuracy of the measuring device should be such that the total measurement error is a maximum of plus/minus 2 percent. Clearance holes should be usable in accordance with ISO 273 standard. It should be possible to secure the mating parts to prevent rotation relative to the part being tightened. The measuring instrument section should allow continuous recording of the entire tightening sequence and may be of analog or digital type.
The test is performed at an ambient temperature of 10-35 degrees Celsius using a compression force measuring device as described above. Unless otherwise specified, each determination of the friction characteristics of the connection type involves 20 test setups. A new screw, threaded hole, and base are used for each setup. The compression process is performed continuously at the recommended constant speed of 10 rpm. The compression speed should not exceed 25 rpm. The actual compression speed is recorded in the test report. The measured quantities are continuously recorded throughout the entire compression process. Normally, the process is stopped when the desired pre-tensioning force is reached.
When a bolt is tightened using torque, the most common method in automated production lines, only 10-20% of the applied torque stretches the bolt and creates a compressive load. The remaining 80-90% is used to overcome friction. The main reasons for this are as follows:
Small changes in the coefficient of friction cause dramatic changes in the compressive load obtained for the same torque:
In safety-critical automotive applications, even a small variation in friction can lead to inconsistencies in connection performance; this is unacceptable for a company like Volvo, which prioritizes durability and zero-defect quality.
In short, the Volvo STD 5511-719 standard is a corporate technical standard that includes a test method for determining the friction characteristics of threaded fasteners such as bolts, screws, and nuts used in automotive assembly. This standard is important in the automotive industry because consistent and predictable friction behavior in threaded connections is critical for:
This standard defines procedures for measuring the coefficient of friction (total, gear and under-head) under controlled conditions, typically using specialized equipment such as torque/tension test benches. It belongs to the VCS/STD 5511 series of standards, which generally covers test methods related to mechanical connections and couplings. This standard is part of a broader set of Volvo corporate standards (STDs) that are legally binding on suppliers when used as a reference in contracts. These standards ensure quality, interchangeability and performance across Volvo Group companies (including trucks, buses, construction equipment and cars).
Suppliers of fasteners to Volvo must demonstrate compliance with the Volvo STD 5511-719 standard when specific coefficients of friction (typically accompanied by surface treatments such as zinc flake coating, phosphating, or lubricants) are required in drawings, specifications, or purchase orders. This is particularly important for high-strength bolts in chassis, engine, and body applications where precise torque-tension relationships are necessary.
The Volvo STD 5511-719 standard is extremely important because it directly addresses the coefficient of friction, one of the most fundamental and highly variable aspects of the performance of threaded fasteners in automotive vehicles. In modern vehicle assembly (cars, trucks, buses, construction equipment), bolted connections are found everywhere, from engine blocks to chassis, suspension, brakes, and body structures. These connections must provide a precise and reliable compressive load (preloading) to ensure structural integrity, vibration resistance, fatigue life, and overall safety.
In conclusion, this standard reflects Volvo’s strong emphasis on reliable connection technology, a cornerstone of vehicle safety and durability in its engineering philosophy. This is one of the most important friction-related characteristics a supplier, engineer, or researcher working with Volvo fasteners will likely encounter.
For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the Volvo STD 5511-719 standard.
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