The test standard for grinding wheel hardness mainly includes GB/T 2490-2018 "Testing the hardness of bonded abrasive tools", which stipulates two main methods to test the hardness of grinding wheels: sandblasting hardness test and Rockwell hardness test.
The principle of sandblasting hardness test is to use a certain volume of quartz sand, under the action of a certain pressure of high-speed airflow, to spray it onto the surface of the grinding wheel through a nozzle, so that part of the abrasive grains and binders are peeled off, and pits are formed on the surface. The hardness of the grinding tool is expressed by measuring the depth of the pit. This method is suitable for ceramic bond and resin bond grinding wheels with abrasive grain sizes of F36~F1200. Grinding tools with hardness grades of F~L are measured in a 5cm3 sand chamber, and grinding tools with hardness grades of M~Y are measured in a 28cm3 sand chamber.
The principle of Rockwell hardness test is to press a certain mass of standard diamond or steel ball indenter into the surface of the grinding wheel under specified conditions, and determine the hardness of the grinding wheel by measuring the depth of the indentation. This method is suitable for grinding wheels with hardness grades of A~Y.
The hardness of grinding wheels is divided into several levels, including super soft, soft, medium soft, medium, medium hard, hard and super hard, with specific codes ranging from A to Y. The selection of these hardness levels depends on the specific application requirements. For example, softer grinding wheels are suitable for removing large amounts of material, while harder grinding wheels are more suitable for fine processing.
In addition, the inspection items of grinding wheels also include wear inspection, rotation strength inspection, performance inspection, etc. to ensure that the quality and performance of the grinding wheels meet the requirements of use.