The two scales are about equally linear in the 400-600 range. ![]() This chart shows (Grit number * Particle diameter) for both scales:Īs we can see, there is no clear conclusion - the ISO scale is more linear for grits below 400, while the CAMI scale is more linear for grits above 600. Some extra data - I wanted to see whether the ISO scale or the CAMI scale are more linear when comparing grit number and particle diameter. Here is the same data in tabular format: Grit No You can even mix and match sandpaper from the two scales without issue. In other words, for woodworking, it does not matter which scale you use until you get to grits 360 and above. As you can see, the difference between the two scales is <25% up to 320 grit. The left axis indicates the grit diameter in um, and the right axis indicates the percentage ratio between CAMI and ISO grits. Here is a chart showing the grit size and the ration of grit sizes for numbers from 24 to 1000: ![]() The tricky part is that the two grit numbers are not equivalent - for example, P360 is rougher than 360. “220”), while the ISO grit size is designated by the letter “P” followed by a number, e.g. The CAMI grit size is designated by a number (e.g. One approach to Surface Finish is to use abrasives or sand the surface. You will then be ready to purchase the correct sandpaper and tools for your project to go smoothly.There are two main classifications of sandpaper: the American CAMI/ANSI standard, and the international ISO/FEPA standard that is replacing it. Here is a chart table showing how Roughness Grade Numbers convert to Ra numbers: Roughness Grade Numbers and Ra Measures Surface Roughness of Abrasive Grits and Sandpaper. This sandpaper is often used for final sanding before a project is completed.Įxtra-fine Sandpaper, including paper with 240-grit to 600-grit, is used between paintings or varnishing and is best suited for polishing jobs.įamiliarize yourself with these sandpaper grits before hitting the hardware aisle. Medium Sandpaper ranges from 60- to 100-grit paper and is used with final shaping, primary sanding, and removing of planning marks on wood.įine Sandpaper, ranging from 120- to 220-grit, is used in most home workshops. This sandpaper runs typically in the 40- to 50-grit range. It ranges from 24- to 36-grit sandpaper.Ĭoarse Sandpaper works best on shaping rough wood or removing previous finishes like polyurethane. Remember these characteristics of the various levels of coarseness.Įxtra-coarse Sandpaper is used primarily for tough jobs like removing paint and varnish or sanding old floors. They’re different from flap wheels, which are meant for harder-to-access areas like the insides of pipes or tubes. They’re great tools for removing rust and polishing and shaping metal. Flap discs are grinding wheels that use layered flaps of coated abrasive to sand down surfaces. Some projects may call for a certain coarseness of sandpaper instead of a specific grit. Sandpaper grit can be divided into 4 groups: coarse, medium, fine, and extra fine. Flap Disc Sandpaper Grit Chart For Auto Body Work. The lower the grit number, the larger the grain and coarseness of the sandpaper. The higher the grit number, the smaller the grain and the finer the sandpaper. The size is determined by a gradation scale established by the Coated Abrasive Manufactures Institute (CAMI). Review these recommendations for the best choice for your project.ĭifferent projects require different grit sizes. Selecting the correct grit of sandpaper can be confusing. Use the chart below to find the right mineral, grit coarseness and finish for your application including light-duty cleaning, heavy-duty blending and finishing, and every surface prep task in-between. ![]() These particles are sifted and sorted by size before being applied to paper with adhesive, thus creating the abrasive and handy helper. Despite its name, sandpaper is not actually made of sand instead, it consists of grains or grits from natural or synthetic sources.
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