Derek Cohen (in Perth, Australia)
Hi Roger

This post is more one of adding to Davids' comments rather than challenging anything he wrote. I bow to his wider experience with waterstones.

The 5000 - or something in that range - is a necessary medium once the "micro" bevel becomes a "macro" bevel. That is, as you are getting close to regrinding the hollow as the microbevel has begun to take too long to hone.

As a parallel, when we were testing out the diamond mesh grits, the goal was to find a spacing that reduced the next grit up to the minimum number of strokes to remove scratches. The balance was that we also needed to keep the number of grits to 3 or 4. (Of course, going down to .01 micron does add a little extra complication! ).

The other factor is the steel you are using - just how abrasive-resistant is it? O1 and A2 are not in the same league as HSS (M2) and the PM steels. I would be looking at reducing the "gap" under those circumstances as well.

Does the higher grit (e.g. 30K Shapton) offer any value? Is there a plateau where further sharpening no longer offers anything to woodworking?

I have not used a 30K Shapton. I have used 0.5 micron green compound (from LV), 0.5 micron 3M micro-abrasive sheets. and the 0.1 micron diamond film. I think that the latter is rated about 200K micron.

The simple answer is that the difference can be felt and seen. That it may not last as long as some would consider to be cost-effective is another issue altogether. There is a law of diminishing returns on everything, as we know. My opinion is, that if the work involved requires the extra control needed (not everything does), then the higher grits are just another tool to get the job done properly.

It is not necessary to go out and purchase a 30K stone. There are the alternatives such as green compound and, recently, the diamond mesh.

Regards from Perth

Derek