I realize that the thread title seems like clickbait. Who would ever hone a razor on a 200-400 grit stone?
My answer: someone who had spent 3000 passes on a Shapton Glass 500 in order to get a ding out of a kamisori.
It's not just that kamisori. I've been buying messed-up Japanese razors on eBay, and trying to reshape them according to my standard, which is: the bevel is entirely flat. If you put the razor on a flattened fine stone, the scratches go all the way to the edge along the entire bevel. This can be a surprisingly hard thing to achieve.
I do know about the tricks, the pressing and the X-strokes and the windshield wiper and the tape and all that. I don't want to use them. I want perfectly flat bevels, and I am willing to pay the price for them.
That price is high, especially for the steels used in Japanese razors. So naturally I started to wonder about coarse stones, and that has opened up a whole new world for me. I'd like to report what I've discovered, and invite the advice of anyone who has swum in these waters.
Discovery 1: Slurry is the enemy
Slurry is a wonderful thing when honing on a fine stone. It speeds things up, and seems to aid in polishing. Yes, you can get some more refinement by doing some final passes with just water, and you should. But there's no harm in riding the slurry train as far as it will take you.
On a coarse stone, that is completely untrue. Kick up any slurry at all, and you are inviting edge dings. Tons of edge dings. It's just awful. You can feel the horrible rocks rolling around under your delicate edge, and the microscope will show just what a mistake you made in persisting at all, once you feel that.
So now I hone on coarse stones under a stream of running water. Exception: vitrified diamond stones. I'm not sure they even know what slurry is.
Discovery 2: Pressure is the enemy
Pressure makes slurry. It also invites unevenness. On coarse diamond stones, it makes scratches so deep that you're not really saving any time, because you're going to do even more work, later, to get rid of those scratches. Every one you don't deal with becomes a ding in the edge at the end of the process.
Discovery 3: Add those two together, and coarse stones aren't that fast.
A 300 grit resin-bonded diamond stone turns out to be a pussycat under light-moderate pressure and running water.
The Shapton Glass 220 turns into a barber hone. Really. The normal word on this stone is that if you don't use it with a lot of pressure, it glazes really fast. True. The interesting thing is that once it glazes, it puts quite fine scratches on the edge. Maybe 800-1000 grit? It's the same principal as a barber hone, and I think it comes from the combination of coarseness and a hard binder. It's a useful quality, because you can judge whether the bevel is truly flat without going up to finer stones, discovering a lack of flatness that was not apparent at the coarser grit, then falling back.
Another observation: running your finger over a stone, and judging its smoothness, is not proportional to grit if you are comparing two different lines of stones. The ones that feel smoother are more likely to make good coarse razor hones. Shapton Glass is tops in this area, above the 220, which is why I have ordered a 320 to complement my 500.
This is all still a work in progress, but it seemed like enough to relate, and to solicit your thoughts.
My answer: someone who had spent 3000 passes on a Shapton Glass 500 in order to get a ding out of a kamisori.
It's not just that kamisori. I've been buying messed-up Japanese razors on eBay, and trying to reshape them according to my standard, which is: the bevel is entirely flat. If you put the razor on a flattened fine stone, the scratches go all the way to the edge along the entire bevel. This can be a surprisingly hard thing to achieve.
I do know about the tricks, the pressing and the X-strokes and the windshield wiper and the tape and all that. I don't want to use them. I want perfectly flat bevels, and I am willing to pay the price for them.
That price is high, especially for the steels used in Japanese razors. So naturally I started to wonder about coarse stones, and that has opened up a whole new world for me. I'd like to report what I've discovered, and invite the advice of anyone who has swum in these waters.
Discovery 1: Slurry is the enemy
Slurry is a wonderful thing when honing on a fine stone. It speeds things up, and seems to aid in polishing. Yes, you can get some more refinement by doing some final passes with just water, and you should. But there's no harm in riding the slurry train as far as it will take you.
On a coarse stone, that is completely untrue. Kick up any slurry at all, and you are inviting edge dings. Tons of edge dings. It's just awful. You can feel the horrible rocks rolling around under your delicate edge, and the microscope will show just what a mistake you made in persisting at all, once you feel that.
So now I hone on coarse stones under a stream of running water. Exception: vitrified diamond stones. I'm not sure they even know what slurry is.
Discovery 2: Pressure is the enemy
Pressure makes slurry. It also invites unevenness. On coarse diamond stones, it makes scratches so deep that you're not really saving any time, because you're going to do even more work, later, to get rid of those scratches. Every one you don't deal with becomes a ding in the edge at the end of the process.
Discovery 3: Add those two together, and coarse stones aren't that fast.
A 300 grit resin-bonded diamond stone turns out to be a pussycat under light-moderate pressure and running water.
The Shapton Glass 220 turns into a barber hone. Really. The normal word on this stone is that if you don't use it with a lot of pressure, it glazes really fast. True. The interesting thing is that once it glazes, it puts quite fine scratches on the edge. Maybe 800-1000 grit? It's the same principal as a barber hone, and I think it comes from the combination of coarseness and a hard binder. It's a useful quality, because you can judge whether the bevel is truly flat without going up to finer stones, discovering a lack of flatness that was not apparent at the coarser grit, then falling back.
Another observation: running your finger over a stone, and judging its smoothness, is not proportional to grit if you are comparing two different lines of stones. The ones that feel smoother are more likely to make good coarse razor hones. Shapton Glass is tops in this area, above the 220, which is why I have ordered a 320 to complement my 500.
This is all still a work in progress, but it seemed like enough to relate, and to solicit your thoughts.
