There may be various types of unqualified grinding wheels, and we have also learned some about them, as well as some that we have not yet understood. Today, we will learn about some unqualified contents of grinding wheels, such as unqualified hardness, unqualified end face runout, radial runout, and unqualified aperture. Let's take a closer look!
1) Unqualified hardness
Grinding wheel hardness refers to the resistance of the binder to the detachment of abrasive particles from the surface of the grinding wheel under external forces, or is understood as the difficulty of abrasive particles detachment from the surface of the grinding wheel. Hardness can accurately reflect the grinding performance of grinding wheels and is one of the important indicators to measure the quality of grinding wheels. There are two requirements for assessing the hardness of grinding wheels:
The uniformity of hardness (the difference between the maximum and minimum hardness values of each measured point) should comply with the provisions of the standard The compliance requirement for hardness is that the average hardness value (arithmetic mean of hardness values measured at each measuring point) should be within the allowable range specified in the standard. The proportion of hardness failures is also quite high, for example, the hardness failure of flat grinding wheels exceeds 20% of the total number of failures.
2) Unqualified end face and radial runout
Unqualified end face and radial runout can cause deviation and affect the balance performance of the grinding wheel during rotation, which can have adverse effects on the machine tool and workpiece. Therefore, it should be controlled within the allowable range.
3) Unqualified aperture
The inner hole of the grinding wheel is the installation reference, and the unqualified diameter of the grinding wheel is listed as a "serious defect" in the standard. The larger the aperture, the eccentricity of the grinding wheel will occur after installation, causing the grinding wheel to be unbalanced. When rotating at high speed, it will intensify vibration, affect the grinding quality, and even cause the grinding wheel to break and equipment damage. If the aperture is too small and the grinding wheel cannot be installed, it cannot be used. If it is forcibly installed, it can scratch the spindle and may also cause dark damage to the grinding wheel, causing it to break during operation and easily leading to accidents. The situation of unqualified aperture is the most serious in spot checks. 16.7% of the total unqualified flat grinding wheels and 58.2% of the total unqualified cymbal grinding wheels.