Home / News & Blog / Abrasive Blog / Abrasive Grain Size Selection under Different Grinding Conditions
The selection of abrasive grit size mainly considers grinding efficiency and the requirements for the workpiece’s surface roughness. We can select the appropriate abrasive grains based on the following points:
① When the workpiece machining accuracy requirements are high and the surface roughness value is low, abrasives with finer abrasive grit sizes should be selected. The smaller the abrasive grain size, the more abrasive grains are involved in cutting, resulting in smaller cutting marks left on the workpiece surface. This leads to a lower surface roughness value. However, the selection of abrasive grit size must also be considered in conjunction with the grinding conditions. If the grinding amount is small and the wheel dressing is fine, selecting coarser abrasive grit sizes can still achieve a lower surface roughness value on the workpiece.
② When the contact area between the grinding tool and the workpiece surface is relatively large, or the grinding depth is also large, coarser abrasive grit should be used. Coarser abrasive grains have less friction with the workpiece surface and generate less heat. Therefore, when grinding a flat surface with the end of the grinding wheel, the abrasive grain size can be coarser than when grinding a flat surface with the periphery of the grinding wheel.
Usually, surface grinding uses a grinding wheel with a grit of 36#～46#, and the workpiece surface roughness value Ra can reach 0.8～0.4μm. If the grinding wheel speed vs is increased and the grinding depth ap is reduced, the workpiece surface roughness value Ra can reach 0.4～0.2μm. When fine grinding, abrasives with a grit of 150#～240# are used, and the workpiece surface roughness value Ra reaches 0.2μm or lower. When mirror grinding, a graphite grinding wheel with a resin bond of micro powder W10～W7 abrasive grit is selected, and the workpiece surface roughness Ra can reach 0.012μm.
③ During rough grinding, the material removal and grinding depth are relatively large, so the abrasive grit size should be coarser than in fine grinding to improve production efficiency.
④ For cutting and slotting processes, abrasives with coarser abrasive grit, loose structure, and higher hardness should be used.
⑤ When grinding ductile metals and soft metals, such as brass, copper, and soft bronze, the surface of the grinding tool is easily blocked by chips, so coarser abrasive grains should be used.
⑥ For grinding materials with high hardness, such as quenched steel and alloy steel, coarser abrasive grains should be selected. When grinding hard metals, such as cemented carbide, due to the material’s poor thermal conductivity, which can lead to burning and cracking, it is advisable to use coarser abrasive grit. For grinding thin or thin-walled workpieces, which are prone to heat deformation, coarser abrasive grains should also be used.
⑦ For workpieces with small cutting allowances or where the contact area between the abrasive tool and the workpiece is small, finer abrasive grit can be selected. Compared to abrasives used for dry grinding, those used for wet grinding can have a finer abrasive grain size.
⑧ When machining on a rigid grinding machine, coarser abrasive grains can be selected.
⑨ During profile grinding, the wheel surface should maintain its shape well, so finer abrasive grit should be selected.
⑩ During high-speed grinding, to improve grinding efficiency, the abrasive grit size should be finer by 1 to 2 grit numbers compared to normal grinding. This is because finer abrasive grains are sharper and can more easily cut into the workpiece. Additionally, there are more cutting abrasive grains per unit area of the wheel, and the force on each abrasive grain is smaller, making it less likely for the abrasives to become dull. However, the abrasive grit size during high-speed grinding should not be too fine, as this would worsen chip removal conditions and reduce grinding efficiency.
In general, medium-grit abrasives are the most commonly used. Fine-grit abrasives are usually only used for fine grinding, lapping, and polishing. In mass production, abrasives with coarser abrasive grit sizes should be selected, as long as the surface roughness requirements of the workpiece are met, to improve production efficiency. However, in small-batch or single-piece production, where the focus is generally on the machining quality of the workpiece, selecting finer abrasive grains is more beneficial. The application range of abrasives with different grit sizes is shown in Table 2-9.
Table 2-9: Application Range of Abrasives with Different Grain Sizes
| Abrasive Grain Size | Application Range |
| Before 14# | Used for rough grinding or heavy-duty grinding of steel billets, polishing leather, grinding salt, grinding floors, and sandblasting rust removal. |
| 14#～30# | Used for grinding steel billets, deburring castings, cutting steel billets and steel pipes, coarse grinding of surfaces, and grinding marble and refractory materials. |
| 30#～60# | Generally used for coarse grinding of quenched or non-quenched steel parts, brass, and hard metals such as cemented carbide on surface grinders, cylindrical grinders, centerless grinders, tool grinders, and other grinding machines. |
| 60#～100# | Used for fine grinding, tool sharpening, gear grinding, etc. |
| 100#～240# | Used for sharpening various tools, rough grinding, fine grinding, honing, and thread grinding. |
| 150#～W20# | Used for fine grinding, honing, thread grinding, instrument parts, and gear fine grinding. |
| W28 and Finer | Used for super-fine grinding, mirror polishing, fine grinding, and polishing. |
Conclusion
The selection of the appropriate abrasive grit size is crucial for achieving the desired balance between grinding efficiency, surface quality, and overall production goals. Finer abrasive grains are ideal for high-precision work, where a smooth surface finish and low surface roughness are required. Coarser abrasives, on the other hand, excel in rough grinding, cutting, and material removal, particularly in high-production environments where efficiency is prioritized.
Understanding the factors influencing abrasive grit size selection, such as the workpiece material, grinding depth, machine rigidity, and whether the grinding process is wet or dry, allows for more informed and effective decision-making. By considering these parameters, manufacturers can optimize the grinding process, enhance product quality, and improve overall operational efficiency.
In summary, selecting the right abrasive grit size is not only essential for achieving optimal results but also plays a significant role in streamlining the grinding process to meet specific production and quality requirements.
