Which edge lasts longer - 600# or 6000#?

[derekcohen]

Russell, the 600 is already more rounded.

Regards from Perth

Derek

[Robson Valley]

I think that the 600 edge will still be, say, 28 degrees. However, the grit particle size will leave many "run-out" scratches which go all the way to the edge. Those make the edge highly variable in thickness = lots of little, flat teeth, side by side.
I don't see that I encounter any uniform blunting of the entire edge at all. Over time in use, what I do see is an increasing number of "light-sparks" as bits of the edge crumple to reflect a very strong incident light. I have been using a 20X magnifier to observe this in one spoke shave blade when compared with the other, unused blade. Discouraging, but I can follow the progress. A few swipes on 600, then the same or more on 1500 makes a smoother edge with smaller run-out scratches. Honing the edge (chrome green, 0.5 micron) only changes the scale of the scratching.

This is why I think the refined edge last longer. There's more uniformity.

Remember that the reported grit sizes are "nominal" particle size. Although the standard deviation may be small, I suspect that there's a (statistically) 'normal' distribution of particle sizes. Some bigger, some smaller. Quality control can only narrow down, never eliminate that distribution.