Stone Grading - How's it work?

[Indymac]

I have just started using my new Tormek.  I was a confirmed Scarry Sharp (cheap) user but decided to bite the bullet at the recent Indy WW show.  When using the Scarry Sharp system I had to be carefull not to drag the larger grit over to the next finer grit sandpaper.  With the Tormek I use this magic gradinig stone to "change grits" and it works pretty well.  The engineer in me want's to know how the grader works. If it fractures the coarse grit particles making them smaller (1000 grit?) what makes them stay on the stone?  I would think the water bath would wash them off.

Somehow the finer grit stays on the stone.  How long does it stay "fine"? Does the amount of time you grade the stone improve the quality of the fine grind? (I have noticed that I get a few coarse scratches on the tool, not enough to effect the sharpness of the tool but not something I'd get with my old scarry sharp system and going up to 2000 grit).

Haven't used the system to sharpen my turning tools yet which is the main reason I got the system.  Scary sharp does great for flat edge tools but does nothing for gouges and the like.  Good machine and well built.  I just need to get further up the learning curve where it's not so steep.

Mac

[Jeff Farris]

When the stone grader fractures the aluminum oxide crystals, it does not pull them out of the binder that holds the stone together.  You will notice that the smooth side of the stone grader will wear.  In fact, it works better once it has the curve of the stone cut into it.  If you are still seeing heavier scratches after using the grader, there are two possibilities.  One is that you need to spend a bit more time using a bit more pressure with the grader.  The second is that you need to spend a bit more time with the fine cut on your tool.  

As for how long the graded surface will last, it depends on the tools you are sharpening.  On flat surfaces (chisels, plane irons, skews, etc) the surface will stay smooth until you use the opposite side of the grader to open the surface up again.  On gouges, you have a couple of minutes of light pressure grinding before you push through the polished surface and reach the more aggressive, larger crystals.