This is a national standard method for the precise measurement of transverse bending (or curvature) of thermostatic bimetals and strips (which can also be extended to other materials). The method aims to evaluate the natural bending deformation of materials in the width direction, which is crucial for the product quality and performance of precision functional materials such as thermostatic bimetals. To perform the measurement, the standard specifies a specialized "transverse bending measuring instrument" (or measurement devices based on the same principle). The core of the method involves freely placing the sample on the instrument platform under specific test conditions (such as a temperature of 24±2°C). The deflection value of its center point from the platform is measured using a precision measurement device, and then the "transverse bending radius of curvature calculation formula" explicitly provided in the standard is used to convert the deflection data into the final result characterizing the degree of bending, thereby achieving objective and consistent evaluation.