Stroke Direction

Interesting. Is it worth also trying a scrubbing motion rather than pure upstokes or pure downstrokes? Or would that be futile?

After you’d finished the progression and did the final grit, how many strokes did you do with the final stone?

And 34 complete progression sharpenings on the 600 grit stones alone? Wow, this must have taken you ages.

I was also wondering about testing the scrubbing though I’m not sure it would work well. I say that because whenever I’m finishing a knife, I find that anything beyond alternating from side to side, one stroke at a time, raises a burr and I think that would decrease the sharpness. Still, it’s a great question and definitely worth testing. I think we’d need to establish exactly how long one scrubs or uses a circular motion per side. Another thing I’d like to test is what effect sharpening parallel to the edge has.

That’s a very interesting observation! I normally use sweeping passes up and away from me until I get to the final stone and then use edge leading passes from the heel to the tip. Maybe I have been getting the optimal edges all along! 🙂

I know that it makes a HUGE huge difference in cutting ability if you maximize the direction of your grind for the way the knife is used.

I’ve been using the exact same technique for a long time and it has always appeared to work best. It’s nice to see it quantitatively as well.

I took the previous test a step further and completed an additional 5 Edge Leading strokes per side and then took another 10 measurements. Here are my results:

Edge Leading AVG = 223g (Averaged from 10 measurements)

The additional 5 strokes per side brought us to a 19.4% improvement from the original blade that was prepared using only Edge Trailing strokes.

Could the edge trailing be leaving a bit of a burr?

I was curious about this as well so took both blades under the microscope at 2000x. In the back of my mind I had an alternate theory and what I saw under the scope may confirm it:

100# Diamond Plates – Edge Trailing Strokes 2000x Magnification

100# Diamond Plates – Edge Leading Strokes 2000x Magnification

I was fascinated to see the toothy appearance of the edge sharpened with leading strokes.

* Please disregard the legend at the bottom of the pictures. I’d forgotten to switch the magnification in the scope software so it’s reading lengths as though they were at 800x instead of 2000x.

Very interesting, I would have thought that edge trailing would have given more teeth. For some reason my natural assumption was that edge leading would flatten the peaks (teeth) more but I guess it doesn’t.

But teeth only help with slicing, not push cutting. How does your sharpness testing Jig work? Does it press down flat (no slicing) or does it move the knife in a sawing motion? Sorry if that’s been answered elsewhere, I did look at the specs for the sharpness tester but to be honest it was a bit above my head so I gave up 🙂

I was assuming more teeth from edge trailing as well which is why the images surprised me. The sharpness testing jig works by applying downward force on the blade. There is no slicing motion. I’m thinking that the force is being concentrated on the tallest of the teeth, resulting in a much greater force per distance of blade on the peaks and rupturing the tape more easily. With the smoother blade from the trailing strokes, the force would be more evenly distributed requiring greater force to rupture the tape. I can definitely see the need for additional tests for cutting ability with each grit/stroke direction i.e. does one shave better than another, push cut paper etc…?