How polished does a primary bevel have to be if I'm going to put on a microbevel?

[brancron]

What does it matter if the primary bevel is rough if a microbevel is going to be put on? Could you get a primary bevel with the Sharpmaker's diamond stones and then go straight to a microbevel with the fine ones?

Another question: in the Sharpmaker video, Sal says that the 30 degree setting is for working on the primary bevel, and he recommends sticking with the 40 degree setting. This presumably means that he's saying only work on the microbevel. But why then does he recommend 20 strokes per side on the brown and white stones? Isn't this way more than is needed for a microbevel?

I'm confused about these things. Sorry if my questions are hard to make sense of!

 

[BellaBlades]

I just did this on my sebbie. Reprofiled to 15dps with diamond rods. Then I worked the medium gray stones corners to flats, then the whites. Only 40 strokes each. This made for a good edge that would cut news print, just not fully refined. I stripped the edge with both black then green compound. All it took after that was 4 very gentle strokes per side on the white flats. Sharpest edge I ever made. It really payed off refining the main edge 95% of the way first. Making the micro bevel minimal but so easy to obtain a fast perfect final edge. I have done it directly from diamonds on other knives. But the extra work goes a long way.
Matt

 

[Obsessed with Edges]

User preference, adapted to one's own needs & uses, basically.

If the primary bevels are very wide, such as with a Scandi grind, a more polished finish on the primary bevels can make cutting much smoother/slicker in thick & tough materials (cardboard, leather, wood, etc). It'll help to prevent or minimize binding* of the blade in the material, as can happen if the primary (& sometimes the whole blade) is finished very coarsely. The larger the surface area in direct contact with material being cut, the more difference it makes.

For the microbevel itself, whatever works best for your needs is what is 'best'. Sometimes a polished primary (a.k.a. 'back bevel', as defined by the Sharpmaker), and a very toothy microbevel can be very useful for immediate 'bite' when cutting into the surface, combined with smoother slicing in thicker material.

* = I've repeatedly noticed that slicing something as simple as an apple can be very difficult with a coarsely-finished blade, because the rough finish really binds it up; an apple has a tendency to clamp against the blade like a vise, when the blade gets fully into the cut. A more polished finish makes a big difference.


David

 

[Jamesh Bond]

What does it matter if the primary bevel is rough if a microbevel is going to be put on? Could you get a primary bevel with the Sharpmaker's diamond stones and then go straight to a microbevel with the fine ones?

Another question: in the Sharpmaker video, Sal says that the 30 degree setting is for working on the primary bevel, and he recommends sticking with the 40 degree setting. This presumably means that he's saying only work on the microbevel. But why then does he recommend 20 strokes per side on the brown and white stones? Isn't this way more than is needed for a microbevel?

I'm confused about these things. Sorry if my questions are hard to make sense of!

What they said.

As to the sharpmaker instruction question, dont overthink it. The excessive amount of strokes is nothing more than a number to guarantee clueless people an edge without getting into theory. To someone more educated in sharpening theory, such as a knife knut, use your knowledge.