1. Confirm the nominal thread diameter: Measure the major diameter of the nut's internal thread using calipers. Compare this to the standard to determine the core specification. Common markings include M3, M4, M5, M6, M8, and M10, which are the core basis for determining the specification.
2. Measure the width across flats: Measure the distance between the two parallel sides of the nut using calipers. Nuts of the same specification from different standards have different widths across flats. For example, an M8 nut in GB6170 has 13mm across flats, while the older standard GB52 has 14mm. This can be used to distinguish nuts from different standards.
3. Check the nut thickness: Measure the overall height of the nut to distinguish between Type 1 standard nuts, Type 2 thick nuts, and thin nuts. Different thicknesses correspond to different usage scenarios and standard numbers.
4. Confirm the thread pitch and type: Distinguish between coarse and fine threads, and determine whether it is a metric, imperial, or American thread to avoid incompatible nuts and bolts.
5. Check the markings. Qualified nuts will have markings indicating their specifications and performance grades, such as grade 8 or A2-70, which can be read directly to confirm their specifications and strength properties.
