Chris "Anagarika";15612716 said:
Martin,
Question: why is the edge trailing move at final/deburr phase on the stone?
I recalled Jason sometimes do that too, and if not mistaken, Murray Carter as well.
In my own way, my left hand is more consistent & flat than my right hand (I switch hand when switching sides), although I'm right handed. I always sharpen edge facing away as to see the spine distance from stone.
Chris, not a simple answer to that. It all depends on the stone composition.
If I'm working with a hard, durable stone - India, Arkansas, diamond plate, ceramic - I'll finish with a leading pass and any backhoning will be done on paper over a stone or Washboard.
Most of the time I'm working with some sort of waterstone or SiC wet/dry over a Washboard - in that case the abrasive has some mobility. If so, (and I admit not being able to prove this microscopically...yet) a few backhone passes will result in the abrasive not biting as deep across the apex and not catching deep enough in the steel to draw out a burr. My theory is the apex becomes thinner across yet still has the same amount of up and down variation at a given grit compared to finishing with a push stroke. This makes a catchier edge and allows some nice and fairly long-lasting cutting qualities in terms of push and draw efficiency.
If the abrasive has essentially zero mobility, finishing with a backhone pass is liable to create small burring. When working off a diamond plate (my third most common abrasive) I don't bother trying to finish with a trailing pass.
I have to wonder if your better results using the left hand aren't because the right hand fingertips are better at modulating pressure or maybe just by chance have better finger placement. Perhaps the left hand fingertips are interferring with the process a bit by chance. This is the sort of stuff that really had me studying my hands and finally approaching the issue as one of mechnical advantage. If certain ways of holding the tool are more advantageous, then why? And what can I do to eliminate some of my problem areas.
I also have those hours of looking at edges under the microscope and that can be merciless - it doesn't lie, so any areas of the edge that are not homogenous compared to the rest are due to technique failure or inattention. Doesn't matter if there's variation in the stone composition (per a waterstone or mineral fracturing on a SiC stone) as long as it is a distribution within a range, any variation in edge appearance will likewise fall within that range. Anything outside that is operator error and can be corrected. It might not make the edge cut any better overall, but is a big help in eliminating problem areas.
The last real holdout for me was the heel on the left side (downside when edge facing away). That's when I realized my offhand fingertips were fighting the process by pushing too far up the bevel and making more variation than should be there. Sooo, get the index finger out of the mix, bend the fingers to direct the stabilizing force more down, lower the palm when possible.
Of course, I'm still working on all of this...
