Uniform Realization of the Unit of Torque in the US

Torque measurements are used heavily during product assembly and testing throughout the aerospace, automotive, and manufacturing sectors. Uncertainty evaluations surrounding the measurements are based upon current best efforts by private and independent organizations. The lack of a singular national torque standards laboratory in the U.S. requires time-consuming and costly maneuvers by each of multiple individual users throughout the supply chain to justify their own systems to even a basic level of uncertainty acceptance by other users. For example recalling a single jet engine due to any problem including poor assembly of torqued components can trigger costs to the manufacturer that begin at $500,000. The human and capital costs can be far higher, of course, when improper torque values are not identified and component failure occurs.

In response to the US industry needs, this project will provide the tools and measurement methods required to assist the secondary calibration laboratories to identify and resolve the technical causes for the current measurement disagreements. The project approach is to improve the secondary calibration system in the U.S. by improving NIST torque measurement capabilities to decrease the measurement uncertainty and provide a reference torque value at a single targeted range, contributing to planning and execution of a torque measurement comparison among U.S. secondary laboratories, analyzing comparison results and identifying areas for improvement in the secondary system, and supporting development of torque metrology standards within the ASTM Mechanical Testing committee.

It is expected that this project will result in a more uniform and reliable realization and dissemination system for the SI derived unit of torque in the United States. The benefit to the government will be that NIST is positioned to guide U.S. industrial torque metrology practices, requirements, and standards. U.S. industry will benefit from validation of the U.S. torque measurement system and will achieve comparability of industrial torque measurements through uniform practices and SI traceability.

• Designed and fabricated specialty components and adapters for torque load cell installation to the NIST torque machine.
• Performed the first torque calibration using the complete setup of the NIST torque machine and a commercial torque load cell.
• Evaluated the integrity of the torque machine setup which resulted in a redesign of the adapter parts for improved durability.
• Developed a unique supported torque arm methodology that will decrease torque measurement uncertainties.