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    Ultimate Guide: Diamond Wheel Grit Sizes & Surface Finishes

    Updated: June 20, 2024 Published: April 17, 2024

    Discover the impact of diamond wheel grit sizes on surface finishes and learn how to achieve the perfect finish for your material.

    Aerospace industry (1)

    Understanding Diamond Wheel Grit Sizes

    Diamond wheel grit sizes refer to the size of the abrasive particles on the wheel's surface. These particles determine the aggressiveness of the wheel and its ability to remove material. 

    The smaller the grit size, the finer the abrasive particles and the smoother the finish it can achieve. On the other hand, larger grit sizes have coarser particles that result in a rougher finish. It's important to choose the right grit size based on the desired surface finish for your material.

    Impact of Grit Size on Surface Finishes

    The grit size of a diamond wheel has a significant impact on the surface finish of the material being worked on. As mentioned earlier, smaller grit sizes produce finer finishes, while larger grit sizes result in rougher finishes.

    When using a smaller grit size, the abrasive particles remove material more gently and evenly, resulting in a smoother and more polished finish. On the other hand, larger grit sizes tend to remove material more aggressively, leaving behind larger lines or pits on the surface.

    The choice of grit size depends on the specific requirements of the application. For example, if you need a high-quality, mirror-like finish, you would opt for a smaller grit size. However, if surface imperfections are acceptable or if you need to remove a significant amount of material quickly, a larger grit size might be more suitable.

    Factors Affecting Surface Finish

    While grit size plays a crucial role in determining surface finish, it is not the only factor that affects the final result. Several other factors can influence the surface finish achieved with diamond wheels, including:

    - Type of material: Different materials have different hardness levels, which can affect the interaction between the abrasive particles and the surface. Softer materials may require a different grit size compared to harder materials to achieve the same finish.

    - Wet or dry grinding: The presence of coolant or lubricant during grinding can impact the surface finish. Wet grinding tends to produce a smoother finish compared to dry grinding.

    - RPMs: The speed at which the wheel rotates can affect the aggressiveness of the cutting action and, consequently, the surface finish. Higher RPMs may result in a smoother finish.

    - Depth of cut: The depth to which the wheel cuts into the material can also impact the surface finish. Deeper cuts may result in a rougher finish.

    Considering these factors along with the appropriate grit size is essential for achieving the desired surface finish.

    Chart of Expected RMS Finishes Based on Grit Sizes

    The expected surface finishes based on grit sizes can vary depending on the specific application and material. Here is a general chart that illustrates the relationship between grit size and surface finish: Note: RMS is an industry standard for measuring the roughness of a finish. Typically either RA or RMS is used when measuring the surface finish of a workpiece.

    Eagle Grit Size FEPA Grit Size Expected RMS
    Finish Resin
    Expected RMS
    Finish Plated
    60 251 35-50 -
    80 181 20-30 90-125
    100 151 16-24 64-90
    120 126 14-20 48-64
    150 107 12-17 32-48
    180 91 10-15 24-32
    220 76 8-12 20-24
    240 64 7-11 16-20
    320 54 6-10 14-16
    400 46 5-9 13-14
    600 30 3-8 12-13

    This chart provides a rough guideline, but it's important to note that actual results may vary based on the factors mentioned earlier. 

    Tips for Achieving Optimal Surface Finishes

    To achieve the optimal surface finish with diamond wheels, consider the following tips:

    - Select the appropriate grit size based on the desired finish and the material being worked on. Refer to the chart provided earlier as a starting point.

    - Take into account the other factors that can influence surface finish, such as the type of material, wet or dry grinding, RPMs, and depth of cut.

    - Regularly inspect the condition of the diamond wheel and replace it if necessary. Worn-out or damaged wheels can negatively impact the surface finish.

    - Ensure you are using fresh coolant with a filter to remove particulates.

    - Use proper grinding techniques, ensuring consistent pressure and movement across the workpiece.

    - Clean the workpiece thoroughly after grinding to remove any residual abrasive particles that could affect the final finish.

    By following these tips and considering the various factors involved, you can achieve the optimal surface finish for your specific application.


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