Thread: The science of grit numbers

If you start searching for the meaning behind the grit and micron numbers on man made stones you'll end up with the impression we have on natural stones. Pretty much, they don't mean anything.
For Norton, 1 micron is 24k grit, as their 8k is 3 micron but not really, for Naniwa 10-12k is about 1 micron, for Sigma and Suehiro, 10k is 1 micron, and for lapping film and Shapton 15k is 1 micron.
Each company has its own scale, but the grit is closer to the finishing capabilities than the micron scale. It doesn't make sense since both describe the size of particles, but it's true. And you'll see some difference between the 8k from one company to the 8k of another, but they are not too far apart. In the end, what matters is if you are satisfied from the stones of a brand that you have. If not, follow the general advise here; Naniwa chocera 1k, and either 4/8 norton, or 3/8 naniwa superstone. For finishers, use a pasted strop or go for naturals is my opinion. Most of the man made finisher stones can be quite harsh for the skin.

i suck at math. i just use this chart as i only have to match the grid with the company style. Norton uses American standard. Naniwa uses JIS. Not sure about other stones but if you know the micron then you will have an idea of what it may be considered.