With the continuous improvement of metallographic sample preparation technology, more and more metallographic samples are using automatic grinding and polishing methods. However, manual grinding technology, as the foundation of sample preparation technology, is still widely used in teaching and is still being used under special working conditions, and has been using the program established many years ago. One of the main processes is to use metallographic sandpaper as the grinding medium to remove scratches and damaged layers from the sample cutting section. So, how to use metallographic sandpaper for manual grinding and polishing of metallographic samples? Below is a brief introduction.

1、 Sample movement:
Using manual grinding, the general metallographic polishing machine is a single or double disc, which can be operated by one person or two people at the same time.
As shown in the figure above, there is no uniform regulation on grasping the sample with one hand or both hands. It is mainly based on the operation habits of the metallographic engineer that the sample should move in a relative Circular motion motion in the opposite direction of rotation to the grinding plate for grinding and polishing. In addition, the sample should be moved back and forth along the direction of the radius to ensure that the grinding medium on the metallographic sandpaper can be used uniformly, so as not to waste the metallographic sandpaper due to grinding along a fixed trajectory.
As the sample moves back and forth along the radius direction, slightly rotate the wrist. After each step is completed, the sample is rotated 45-90 °?, In this way, the grinding of the sample will not proceed in one direction, making the grinding surface of the sample more evenly stressed.
2、 Grinding and polishing pressure:
How to grasp the pressure during the grinding and polishing process of the sample on metallographic sandpaper? This is indeed a problem. Different operators, different levels of proficiency, and the habits of the operators are all factors that exert pressure on the sample. Quantitative standards cannot be provided here, and only based on experience can appropriate pressure be applied to the ground sample. Generally, regardless of whether the pressure is high or low, the basic principle is to maintain a fixed pressure.

3、 Sample cleaning:
To ensure that the sample is not affected by the coarser grinding particles remaining in the previous metallographic sandpaper during the next grinding and polishing process, it is necessary to clean the sample and grinding disc.
The cleaning of the sample involves first washing the sample in a detergent aqueous solution, followed by rinsing in flowing warm water, followed by rinsing with alcohol, and then drying with warm flowing air.
Before replacing the next layer of metallographic sandpaper, it is necessary to rinse the grinding disc and the iron disc with metallographic sandpaper. Simply use a spray device to rinse with clean water. After thoroughly rinsing the iron disc with metallographic sandpaper, stand on a drainage bracket and let it air dry naturally. Then, the next iron plate with metallographic sandpaper is clamped onto the grinding plate for the next process of grinding and polishing. And so on, until all grinding and polishing are completed.
The above is the traditional operating procedure and method of manually grinding and polishing metallographic samples using metallographic sandpaper. Due to the different materials used for manual grinding and polishing, the purpose of metallographic analysis may vary in the actual sample preparation process. Therefore, the above methods are only for the reference of metallographic engineers.