It does not seem like microbevels are talked about too often...

[iamerror]

It seems like they are a good way to keep an edge by adding some strength and limiting the amount of steel needed to be removed and still keep good cutting performace. It wasn't until recently that I learned what a microbevel even is. I have a few questions about them, though.

1. Say I have a knife that is completely reprofiled to 12 degrees on each side, if I wanted to add a microbevel of 15 degrees, how long does it take to add the microbevel? (maybe an estimated amount of strokes on whatever surface) How do I tell that it is there?

2.Once I completely have the 12 degree bevel and 15 degree microbevel done, what is the best way to maintain this edge? Do you sharpen at both angles (12 and 15 degrees) an equal number of times, only sharpen the bevel, only sharpen the microbevel, etc...?

 

[Cliff Stamp]

1. Say I have a knife that is completely reprofiled to 12 degrees on each side, if I wanted to add a microbevel of 15 degrees, how long does it take to add the microbevel? (maybe an estimated amount of strokes on whatever surface) How do I tell that it is there?

It is about 0.1 mm wide immediately, meaning 1-2 passes. It grows with a power law decrease after that meaning it takes longer to make each additional increase. You can check it with a 10X mag scope that you can buy at radio shack for a few dollars.

2.Once I completely have the 12 degree bevel and 15 degree microbevel done, what is the best way to maintain this edge? Do you sharpen at both angles (12 and 15 degrees) an equal number of times, only sharpen the bevel, only sharpen the microbevel, etc...?

Sharpen the microbevel until it slows down significantly. You will note it takes longer each time. Then resharpen the 12 degree bevel right to the edge again and then reform the edge at 15.

-Cliff

 

[Dog of War]

I agree with everything Cliff has said, but maybe I can offer a couple additional thoughts.

For the most part, I go no higher than medium grit when finishing the primary bevels and relief. I then go directly to fine ceramic, about 1200 grit, either Sharpmaker or Crock Sticks, to add the microbevel. Because the polish of the microbevel is so much higher, you can easily see it in bright light - just a thin, shiny, even "strip" of polished metal right at the edge you can see with the naked eye. You can tell right away if the microbevel isn't uniform ... usually just a few more strokes on the fine ceramic is all that's needed, but sometimes unevenness can be due to a residual wire edge, or just not enough work being done when sharpening the primary bevel.

I suspect, In part because of the big jump in hone grit between primary bevel and microbevel, I find it works best for me to have the microbevel about 5 degrees greater than the primary, for example if I've reprofiled to 12 deg/side, I use a 17 degree microbevel (this is kind of my bog standard for most any general utility blade, BTW, from EDC folder to big chopper.) Often when I've added a 15 deg. microbevel to a 12 deg primary, getting a uniform, clean edge isn't as quick an easy. If you're putting a higher level of polish on the primary then this won't be the case .... in fact cabinetmakers and pro wood workers usually increase the angle by only about 1 deg. when putting a microbevel on chisels and plane irons.

But I also think the bigger differential between primary and microbevel has another advantage: you can thin the primary out more, and still get good edge stability and durability because of the microbevel. There seem to be quite a few popular blades/steels out there that show much better edge holding with a 17 degree microbevel than with 15 degs. So the easy way to achieve much higher cutting performance and still have decent edge stability is with a thinner primary and more obtuse microbevel.

Also as the microbevel "grows" over time, you can simply thin down the shoulder between the microbevel and primary, for example if using a 12 deg. primary and 17 degree microbevel just do a few swipes at 14-15 degrees - medium Sharpmaker is great for this - if you don't want to do a full resharpening.

 

[Buck268]

I would think the finer the finish on the acuter bevel the better as this surface would directly act to split the material being cut.

On my poor stone selection I always finish both edges with my finest option (see my post: "What stone?").

 

[iamerror]

What is the relief? Also, can you elaborate more on the microbevel "growing" over time--why/how does this happen?

 

[gud4u]

The relief grind is the primary bevel. Metal is 'relieved' from the blade to form narrow (smaller included angle) main bevels. That relief grind aids slicing efficiency by reducing the wedging effect as the blade moves through sliced material.

The microbevel is added to reinforce the cutting edge, since the narrow primary bevel tends to weaken the edge when slicing harder materials.

The microbevel seems to 'grow' due to repeated honing of the microbevel surfaces - material is removed and the surface area of the microbevels increases.

At some point - after many honings of the microbevels - the size of the microbevels is large enough that it becomes a significant contributor to wedging. The knife begins to cut as though the enlarged microbevel is the main bevel. At this point, the main bevels are reground to reduce the area of the microbevels.

Hope this helps!