Abrasives in Micron Scale: Grand Logarithmic Grit Chart (version rv.13) printed in A4 size (11 x 8.5") on cardstock paper with UV coating. Copyright "Mr.Wizard".
It is the intent to display a broad range of abrasive particle size information as compactly and intelligibly as possible. Since these cover several orders of magnitude a logarithmic scale is most appropriate. A logarithmic scale also has the property of equidistant spacing for any geometric progression, meaning that a theoretically ideal abrasive series will be uniformly spaced in the chart. Stated another way, two grits that differ by a specific ratio will be a fixed distance apart on the vertical axis of the chart whether they are 1.0 and 1.5 micron or 200 and 300 micron.
The chart started out as a table of conversions from grit number to microns but grew in scope to include products that are directly specified in microns. It is therefore also to a degree a record of availability of products that may be of interest in certain markets. The logarithmic visual representation is intended to be easier to internalize than numbers simply read from a list.
More info in the official README.
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