Stone flattening

stitchawl said:
And that's the facts, Jack!! :thumbup:
Try to visualize what a micro-photo of, say, a 600 grit stone surface would look like after flattening with a 100 grit flattener. The surface would look like a cobblestone street, with high spots and low spots. But a knife blade edge will only contact the high spots, and those will STILL be at 600 grit. Now imagine the surface after flattening with a 1,000 grit stone. Very flat and smooth, but below those very top most flat particles which will be removed after the first stroke of the blade, STILL having a grit size of 600. No matter what you use to flatten a stone you aren't changing its grit size, only its appearance. We are dealing with micro size particles, not cobblestones.


Stitchawl
Click to expand...

What you'll do on a coarse stone lapped with a fine stone (since you want to visualize a micro-photo) is basically "smooth the mountain tops". It may still be a coarse stone, but won't cut as aggressively, and can take quite a while to return to it's aggressive state... often needing to be lapped again before it does. A fine stone lapped with a very coarse stone will create "mountaintops", that will cut more aggressively and leave a rougher scratch pattern... although it will typically smooth out quicker. This is part of the reason you can get different finishes off the same stone, the other being a mud/slurry buildup.

But don't theorize, just go lap two similar stones with two different types of lapping media, and you'll immediately notice a difference, especially on a coarse stone. Most people don't notice it because they don't lap the stone with different media, so they can't tell there is a difference. Since you're an EP fan, you'll really see it on the coarser stones, if for example you lap them with a DMT XC vs. the SiC powder EP provides. The powder will make the stone noticeably more aggressive, and it will cut noticeably better. Take the same SiC powder fresh (not broken down by a coarse stone) and lap the 800 or 1000g stone, and it won't leave near as fine a finish until it's been used for a while. (And it doesn't have anything to do with contaminating the stone).

cbw
 
I find that the flattened stones returns to their best cutting within minutes of use. Doesn't seem to be a problem. Your mileage might vary.


Stitchawl
 
It does... in that same few minutes, I'm done and moving on to the next stone. :)

cbw
 
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