True Grit: Understanding Sharpening Grits

Once you get serious about sharpening, two things happen. Your edges get keener but you get more confused about the “grits” used in the process. A #1,000-grit waterstone isn’t the same grit as #1,000-grit sandpaper. (Heck, #1,000-grit sandpaper in the United States isn’t the same as #1,000-grit sandpaper in Europe.)

The reason is that sandpaper, waterstones, oilstones, diamond stones and silicon carbide stones all use different systems to tell you how coarse or how fine the material is. If you stick with one system and one brand (say, you use Norton waterstones exclusively), this isn’t a problem. Just start with the coarse media and proceed to the fine one.

But if you start mixing brands or systems, you can get in trouble. Here’s an example: Say you want to use a soft Arkansas oilstone as your coarse stone and an extra-fine India (aluminum oxide) stone to finish things up. Well good luck , both of these stones are the same grit (22 micron). Your edge won’t improve when you move to the extra-fine stone.

The good news is that you can convert all sharpening media to microns and get a better picture of where your sharpening stone or paper is in the continuum from cinderblock (coarse) up to baby’s behind (very fine). Now I don’t want to bore you with a discussion of microns, but here’s the short explanation. A micron is a measurement of the diameter of each particle of grit in your stone and paper. Micron is sort for micrometer. One micron is one-millionth of a meter (hey, I just used the metric system). So the smaller the number in microns, the finer the grit.

So with the help of readers and published statistics, I’ve put together a spreadsheet of common sharpening media and converted them to microns for you. The chart covers:

– Man-made stones (silicon carbide and aluminum oxide)
– Oilstones
– Diamond stones
– Waterstones
– Sandpaper (both CAMI and FEPA)
– Other stuff (diamond paste, green compound, ceramic diamond media)

Please keep in mind that these are published statistics; I have no way (or desire) to measure the actual particle size or consistency of the media. I’ll be adding to this chart as I get more statistics, but this chart is a good first stab.

Below you can download an Excel spreadsheet (and modify it if you please) and a pdf of the chart for those readers who aren’t chartered accountants.

– Christopher Schwarz