Microbevels

Here is the Benchmade 9500 Mini Stryker from a regular camera after applying first the convex bevel (16°-20° per side), then the micro-bevel (20° per side):
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The micro-bevel is barely visible to the naked eye.

Applying the micro-bevel was a very quick matter of a few strokes per side with the 1600 grit ceramic stones. My theory for the bevel geometry is the following:

With thin, polished and convex shoulders, drag should be minimal when cutting and because the shoulders are so close up behind the cutting edge, they'll enter the cut quickly, spreading the cut apart and reducing stress on the apex of the edge. The V-grind mirco-bevel should be a more precise cutter than a convex-to-the-edge bevel, reducing some of the deflection I find with purely convex edges. The extra width of the micro-bevel at 20° per side should make it a little tougher. Now for some testing....
 
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Clay, thanks for the experiment and comments. Could you please expand a little regarding this:

The V-grind micro-bevel should be a more precise cutter than a convex-to-the-edge bevel, reducing some of the deflection I find with purely convex edges.

I guess I don't understand convex-to-the-edge causing deflection.

Thanks,

Andrew
 
AFAustin said:
Clay, thanks for the experiment and comments. Could you please expand a little regarding this:

The V-grind micro-bevel should be a more precise cutter than a convex-to-the-edge bevel, reducing some of the deflection I find with purely convex edges.

I guess I don't understand convex-to-the-edge causing deflection.

Thanks,

Andrew
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Hey Andrew,
The curvature causes the blade to deflect whenever it hits resistance. Imagine cutting something that does not have uniform consistency - the side of the knife that hits something harder will be deflected and this is exaggerated with the curvature. A good model for visualizing it is the keel on the bottom of a boat. Without a keel, the bottom of the boat would be unwieldy and would roll around. A more pronounced keel gives you better steering. Chisel ground blade are the most precise, followed by a V-grind, then a V-grind with a micro-bevel.
 
The deflection of a convex edge is often easily seen in slicing through some light paper, like phone book pages. The path of the cut will be radiused or curved, instead of staying straight, as the edge tends to turn away from the 'thicker' side of an asymmetrical convex. All-the-more noticeable on a very thick convex, if it's not evenly matched up. This is a very easy way to see if the edge symmetry is good, because when it's bad, it's impossible to ignore when watching the path of the cut through the paper.

Asymmetrical v-bevels behave the same way, but sometimes the path of the cut might not be as clearly obvious, if the shoulders of the v-bevel hang/snag in the paper (which they'll often do). The 'slick & smooth' nature of a convex usually makes for a longer and more uniform slice into the paper, which makes the deflection easier to see.
 
Obsessed with Edges said:
The deflection of a convex edge is often easily seen in slicing through some light paper, like phone book pages. The path of the cut will be radiused or curved, instead of staying straight, as the edge tends to turn away from the 'thicker' side of an asymmetrical convex. All-the-more noticeable on a very thick convex, if it's not evenly matched up. This is a very easy way to see if the edge symmetry is good, because when it's bad, it's impossible to ignore when watching the path of the cut through the paper.

Asymmetrical v-bevels behave the same way, but sometimes the path of the cut might not be as clearly obvious, if the shoulders of the v-bevel hang/snag in the paper (which they'll often do). The 'slick & smooth' nature of a convex usually makes for a longer and more uniform slice into the paper, which makes the deflection easier to see.
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Nicely said!
 
Ok. Maybe someone can explain this whole micro bevel thing for me. I usually put a back bevel then a secondary on my knives. I work the acute bevel till I raise a burr then polish. Then I do the same for my secondary. Is this a micro bevel? Because what I'm gathering here is you don't raise a burr on the micro. How can an edge cut well if the grinds don't meet? I'm assuming this is what everyone's talking about as it seems only a few strokes per side is needed and in my experience this will not raise a burr no matter how course or fast cutting a stone is especially a very fine one does basically nothing with a few strokes. I've always been under the assumption and my own experience if you don't raise a burr you don't have a sharp knife. Thanks
 
Vicv said:
Ok. Maybe someone can explain this whole micro bevel thing for me. I usually put a back bevel then a secondary on my knives. I work the acute bevel till I raise a burr then polish. Then I do the same for my secondary. Is this a micro bevel? Because what I'm gathering here is you don't raise a burr on the micro. How can an edge cut well if the grinds don't meet? I'm assuming this is what everyone's talking about as it seems only a few strokes per side is needed and in my experience this will not raise a burr no matter how course or fast cutting a stone is especially a very fine one does basically nothing with a few strokes. I've always been under the assumption and my own experience if you don't raise a burr you don't have a sharp knife. Thanks
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Once you've ensured that the bevels meet (by burr detection) when you create the acute back bevel, you're basically guaranteed that the wider micro-bevels will meet as well because you're working of the very edge from the get go of micro-bevel formation.
 
Ok. I just tried it on my lansky with a 17o main with a 20o micro. Not quite those exact numbers as I messed with the angles to make it a larger gap. 30 strokes on each side with the 1000 hone. About as good at paper cutting as before. Can see a tiny shine at the very edge. Then deburred with a cork. Hopefully it'll last longer now. Thanks for the explanation
 
I am curious if it possible that there are a couple of additional benefits to microbevels:

(1) To remedy a bevel that is not perfectly apexed. That is, you got close to a perfect apex on your initial bevel, but then would applying a light and quick micro close any gaps?

(2) To improve stropping results. I know that with my compound-on-leather strops, I sometimes round the edge, doing more harm than good. Would the slight additional shoulder close to the very edge that a micro produces absorb the bulk of the stropping stroke, thus making for the slightest and lightest contact with the micro'd edge and improving results?

I didn't state this very well, but I hope my questions make sense. I would appreciate any insight.

Andrew
 
AFAustin said:
I am curious if it possible that there are a couple of additional benefits to microbevels:

(1) To remedy a bevel that is not perfectly apexed. That is, you got close to a perfect apex on your initial bevel, but then would applying a light and quick micro close any gaps?

(2) To improve stropping results. I know that with my compound-on-leather strops, I sometimes round the edge, doing more harm than good. Would the slight additional shoulder close to the very edge that a micro produces absorb the bulk of the stropping stroke, thus making for the slightest and lightest contact with the micro'd edge and improving results?

I didn't state this very well, but I hope my questions make sense. I would appreciate any insight.

Andrew
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I think the micro-bevel would help with the rounding off an edge when stropping problem. However I don't think it's a very good solution. I know I'm stating the obvious but improving the stropping skills would be the correct fix. I wouldn't want to change the edge formation based on a weakness in another area. I'm not saying this to be mean. I always saw a barber strop his razor quickly and figured it was an easy task. I never thought he was just good at it. I've had a time learning to strop and will still round off an edge when stropping while watching TV because I'm not concentrating. I think the most important thing to remember when stropping is light strokes. Even if they are so light they aren't helping the edge, at least they aren't doing harm. :)

I'm not really sure what you are talking about in your first item.

Jack
 
Jack,

Thanks for your thoughts. What I'm trying to get at, and not stating it very well, is that with some knives I manage to get them sharper with a micro than without, and I'm trying to understand why.

The benefits of a micro are usually stated as (1) sturdier edge, and (2) ease of touch-ups. But I actually seem to get a better edge in the first place, with some knives, by doing a micro.

Andrew
 
AFAustin said:
Jack,

Thanks for your thoughts. What I'm trying to get at, and not stating it very well, is that with some knives I manage to get them sharper with a micro than without, and I'm trying to understand why.

The benefits of a micro are usually stated as (1) sturdier edge, and (2) ease of touch-ups. But I actually seem to get a better edge in the first place, with some knives, by doing a micro.

Andrew
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Ok, gotcha. I'm no expert at all but, the first time I actually needed to use a micro-bevel to get a knife sharp was with ZDP-189. It was the first really hard steel I own. When removing steel from a wider bevel it takes longer and also is harder to keep your angle accurate. After asking for and getting a lot of help and suggestions I believe the best advice was to put a micro-bevel on the edge. By doing this we are removing just a tiny bit of steel which makes getting a sharper edge much easier. Or, it was what worked for me. I'm guessing people with more skill and experience than me may not need a micro-bevel just to get the knife super sharp but it helped me.

This brings up another subject. How big is the micro-bevel? Personally, I use the term "micro-bevel" when the bevel is small enough it's hard to see without looking real close. Once I have removed enough steel from the edge that the two bevel angles are easily visible I prefer to use the term "edge-bevel". Just makes it easier for me to distinguish between the two edges. I've found that an almost invisible micro-bevel results in the stupid sharp edge that we love. The bevel is tiny and at first glace makes the edge even "look" dull. It may have a rounded appearance. But when shaving arm hair, the hairs pop off and put the dog's eye out. :)

Jack
 
Thanks again, Jack. I usually set my bevels with a Work Sharp (mini belt sander) at around 30* inclusive, then use a sharpie and a Sharpmaker to confirm the 30* angle. I touch up with the SM UF rods and strops. I get decent results, but am looking to get to the next level. I've experimented with micros a little in the past, but for whatever reason haven't had stellar results.

I re-read this thread again yesterday and gave micros another try on a few knives. As per your terminology, by "micro" I mean just a few passes on the SM UF rods at 40* inclusive. I got noticeably better results this time, which prompted my post on trying to figure out exactly why.

Andrew
 
On my sujihiki I do a microbevel (keeps edge sharp longer).

On my Yanagi I do a extreme light microbevel (maybe 2-3 passes on 8000 grit).

New sebenza will get slight microbevel as well, seems thin enough.

Do you microbevel on strops or stones? I get better results on stone so my belt strops collect dust...
 
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