The "ideal" angle.

[Critikill]

Pretty new here still and I'm trying to soak up as much information as I can. I've been working on my BK16 recently and I've gotten it hair popping sharp with shallow convex grind (maybe 10-15 degrees a side) using sandpaper, a mousepad, and a strope I made out of leather from a local shoe repair shop (guy gave me some compound for it too!)

I've been watching some videos online to improve my techniques and I found this one.

When I look up edge geometry, I find a lot of basic information but not many specifics. From what I've been reading, and correct me if I'm wrong, a more shallow grind will slice better, but will also retain an edge for a shorter time?

I plan on using my BK16 for bushcraft and food prep, not too much batoning (I have a hatchet for that). Have I made my edge to shallow?

What would be the best angle for general wood work? Is there a "best" angle?

For future reference, how can I figure out the "best" angle for a given knife? Is it based on the slope of the blade face? The thickness of the blade right before the edge? Or is the angle based only on the work I plan to do with the knife?

BTW: still loving the BK16 and can't wait to take it camping in the next couple months (one it cools down a bit... not trying to fry).

PS: My left arm and legs are missing large patches of hair. It looks like I have leprosy now.

 

[Moosez45]

I been using a 40 degree inclusive edge on mine. I prefer a V edge over a convex, but that is each persons choice to make.

Thin cuts. It doesn't take to over the top hard use though. The "wider" the edge, the more surface area you have dragging on the media you are cutting, thus, wearing more of the metal, but with a thinner edge, you also get less separation of the material, i.e. "wedge" so you might feel more drag.

I personally like the thinner edge on cutting knives, and a thicker on on the beaters.

A 30 degree inclusive edge on a crafter and food prepper should be awesome. Just be careful, thinner edges roll a little more often.

Moose

 

[Critikill]

Thin cuts. It doesn't take to over the top hard use though. The "wider" the edge, the more surface area you have dragging on the media you are cutting, thus, wearing more of the metal, but with a thinner edge, you also get less separation of the material, i.e. "wedge" so you might feel more drag.

I personally like the thinner edge on cutting knives, and a thicker on on the beaters.
Moose

So you'd say the angle is based more on the work the knife will be put up to than the rest of the knife's geometry?

 

[parbajtor]

=I plan on using my BK16 for bushcraft and food prep, not too much batoning (I have a hatchet for that). Have I made my edge to shallow?

What would be the best angle for general wood work? Is there a "best" angle?

For future reference, how can I figure out the "best" angle for a given knife? Is it based on the slope of the blade face? The thickness of the blade right before the edge? Or is the angle based only on the work I plan to do with the knife?
.

The angle should be matched to the type of work, but there are also physical limitations imposed by the type of steel and the hardness of the blade.
Woodworking/whittling knives usually have harder steel and shallower angles, but you might need a different slightly wider angle for a knife used on hard or seasoned woods compared to soft or green woods.
Japanese kitchen knives tend to be harder steels and shallower angles which suits slicing rather than chopping when it comes to food prep. You probably need to experiment to find the shallowest angle where the edge chips/rolls with woodworking chores and then widen it by a degree.

 

[Moosez45]

So you'd say the angle is based more on the work the knife will be put up to than the rest of the knife's geometry?

Somewhat. Thicker grinds with thinner edges, put alot of "meat" behind a thinner edge, giving the appearance of a "tough" blade, but will roll or chip easy. Thinner grinds with thin edges, are gonna be a slicing beast.

On my BK16, I went with 20 degrees on both sides, I still baton, beat and work it like I would any other knife of its size. My BK9 has a 25 degrees angle and still works just fine.

My daughters Izula, sharpened at a 25 degree angle, just wouldn't work well for her. SO, I dropped it down, and thinned that edge out, and she can use it much more effectively now. Remember, she's not strong, and can't power through like a grown man can, so the thinner edge helps her out.

Moose

 

[Critikill]

You probably need to experiment to find the shallowest angle where the edge chips/rolls with woodworking chores and then widen it by a degree.

Is there any mathematical way to do this based off blade hardness, thickness, and type of work or is it simple a play by ear and correct as you go type of thing? I feel like finding the idea edge may lose me quite a bit of steal off my knife if I can't find a "formula."

 

[daizee]

The thickness of the primary grind before the edge bevel was applied matters too - if the grind leaves a lot of meat at the edge you may want a shallower angle if finer cutting ability is your goal. This will make the edge bevel 'taller'.

Soo... all of the geometry matters to some degree. The thickness of the original stock along with the height of the blade and the angle of the primary bevel determines how much meat there is at that edge, and how quickly it tapers...

 

[Critikill]

I prefer a V edge over a convex, but that is each persons choice to make.

Can I ask why? From what I've been reading, it seems like a convex edge would be superior in most ways as long as you can learn to sharpen it properly in the field.

The thickness of the primary grind before the edge bevel was applied matters too - if the grind leaves a lot of meat at the edge you may want a shallower angle if finer cutting ability is your goal. This will make the edge bevel 'taller'.

Soo... all of the geometry matters to some degree. The thickness of the original stock along with the height of the blade and the angle of the primary bevel determines how much meat there is at that edge, and how quickly it tapers...

So it sounds like this is something I will have to learn from trial, error, and experience more than something I can read and learn. I can understand that, I just worry it will be an expensive set of "lessons."

 

[Moosez45]

Can I ask why? From what I've been reading, it seems like a convex edge would be superior in most ways as long as you can learn to sharpen it properly in the field.

This is my opinion and only my opinion, take as just that.

Sharp is all determined by symmetry, always has been. Its difficult to get a perfect convex on both sides, since there is no point of reference to begin with. I'm sure someone can make a jig, or some folks can make a symmetric convex, I ain't one of them.

And for me, field sharpening can be an issue, unless you have the skill to sharpen a knife on feral stone and get your convex right on the money.

A V edge is a little more forgiving, IMO.

Plus, if you look at the profile, a v edge will cut the media, then force it apart at the shoulders, creating separation on the shoulder. A convex, will cause the media to follow the edge and up the steel. Jerry Fisk explained the use of the swedge on a BK5 once, and it makes perfect sense. What dulls a blade, is media wearing the edge, and there is just more surface area on a convex edge than a v edge,

These are just my thought, and the reason why I prefer it, easier to sharpen, stays sharper longer, and can be made symmetric and repeated.

But a knife edge is as individual as the person wielding it.

Moose

 

[daizee]

Yes, it takes some experience and some mental visualization to get to the point where you have reached your own ideal - and that's the thing, there is no 'THE' ideal, just yours. Several of the variables depend on how YOU will use the knife.

I like a V-edge because it's easier to tell what's going on, but I strop my v-edges. Stropping is essentially a convex sharpening technique, but when used with only very very fine grits, it just polishes the edge (and shoulder), rather than noticeably removing material.

 

[parbajtor]

Bevels for bushcrafters usually range from 18 degrees through to 25 on each side, depending on the range of likely tasks.
If you're not likely to baton with it, 18 or 19 degrees is a good slightly slicey angle to start with.
As you've already sharpened it to around 15 degrees, I'd put it through it's paces doing some feathersticks and trigger making etc.
on some dry wood and then inspect the edge for chipping or rolling.

 

[Critikill]

These are just my thought, and the reason why I prefer it, easier to sharpen, stays sharper longer, and can be made symmetric and repeated.

From what I've read, a convex blade "stays sharper longer." The theory is that there is more "meat" directly behind the finest part of the edge. Also, even if a convex gets a little dull, the geometry is supposed to allow for easier slicing on convex.

I would assume that the ABS promotes the convex edge because most of us (ABS Smiths) have found that the convex edge provides nearly every aspect you could want in an edge. With a very fine convex edge you get that "scary" sharpness that folks speak of, and because of the extra couple of thousandths thickness just behind/above the edge you achieve much greater durability. The real key to the quality of edge that the convex provides is just that....its shape. A smooth radius means much less cutting resistance than something like the semi-hollow grind you see on many blades. (many of these blades have very obtuse bevels between the "hollow" and the edge, creating much greater cutting resistance) Most of us have also "tweaked" our heat treatment to compliment the particular grind we apply, which is another key element in producing a quality edge.

I can't speak for other ABS Smiths, but I do not apply a full convex to my knives. About 80%-90% of the blade is flat ground to reduce weight, and the last 1/8" to 1/4" of the blade's edge is convexed (the amount of convex depends on the specific blade/knife) I believe that if you look closely at many of the ABS MS knives, you will find they are similar. They will all have some degree of edge bevels, but in most cases those bevels are also radisued rather than flat. It's the transition between an edge bevel and the main blade bevel that makes all the difference.

I personally think that not enough attention is paid to cutting resistance in a blade. A dull blade that is setup/ground to reduce cutting resistance (as in one with a convex edge) will seem to cut as well as a different type of edge configuration that is freshly sharpened. In all actuality, that is why the convex edge shines in the cutting competitions....its not that it stays sharper any longer, its just that the cutting resistance is so low that even after many abusive tasks it still keeps going.
And finally, if the Bladesmith/Knifemaker has done their job correctly, the convex edge will be simple and easy to resharpen once its dull. The convex edge, correctly applied, will be sharp, durable, and easy to resharpen..... Thats probably why most ABS smiths choose to employ it on their knives.

Source

This is again, just one of the many posts I've read, and not something I've had a lot of personal experience with however. I would love to do a side-by-side comparison of the same knife with different edges some day and determine which I like better.

Thanks for the advice from those that gave it. The answers make sense, even if they aren't the answers I want:

But a knife edge is as individual as the person wielding it.

I wish there was a more simple "sharpen it to XX degrees and enjoy your new lightsaber." That would let me know I reached "perfection."

On the plus side, this makes it more of a hobby and I get to try out lots of knives, grinds, metals, shapes, handles, etc.

Take pitty on my wallet...

 

[Critikill]

As you've already sharpened it to around 15 degrees, I'd put it through it's paces doing some feathersticks and trigger making etc. on some dry wood and then inspect the edge for chipping or rolling.

Can you recommend a good way to do this?

 

[Moosez45]

From what I've read, a convex blade "stays sharper longer." The theory is that there is more "meat" directly behind the finest part of the edge. Also, even if a convex gets a little dull, the geometry is supposed to allow for easier slicing on convex.

That hasn't been my experience. I've tried to like a convex edge for years, it just ain't happening. I've got a few custom knives, that sport the convex edge, even one that Jerry Fisk put an edge on for me, I can make a V edge scary sharp, everytime.

Most of the convex edges I've felt, don't come close. Not to say there isn't any good sharp convex edges out there, they seem to to take too long to make and maintain.

Moose

 

[Critikill]

That hasn't been my experience. I've tried to like a convex edge for years, it just ain't happening. I've got a few custom knives, that sport the convex edge, even one that Jerry Fisk put an edge on for me, I can make a V edge scary sharp, everytime.

Most of the convex edges I've felt, don't come close. Not to say there isn't any good sharp convex edges out there, they seem to to take too long to make and maintain.

Moose

Well maybe if I get the edge right you could field test it against a BK16 with a V edge of your angle choice? I'd love to see the results if you'd be willing to write up a comparison Moose.

 

[Moosez45]

Well maybe if I get the edge right you could field test it against a BK16 with a V edge of your angle choice? I'd love to see the results if you'd be willing to write up a comparison Moose.

Either that, or I could send you my BK16, and you could. Either way, if you want to, it can be done.

Moose

 

[Critikill]

Either that, or I could send you my BK16, and you could. Either way, if you want to, it can be done.

Moose

I'd be fine with that too. I figured 1) you may know a bit more about field testing than I do and 2) you probably have more experience/knowledge at determining what makes a good edge and 3)you may not trust the new guy (me). I've been reading enough of this forum to see that there are a lot of guys here that hold you in pretty high regards Moose so I think I could trust you to give my knife back when you're done... thought I could be reading them wrong

Of course this will have to be after I figure out the angle I really like convexed!

 

[Moosez45]

I'd be fine with that too. I figured 1) you may know a bit more about field testing than I do and 2) you probably have more experience/knowledge at determining what makes a good edge and 3)you may not trust the new guy (me). I've been reading enough of this forum to see that there are a lot of guys here that hold you in pretty high regards Moose so I think I could trust you to give my knife back when you're done... thought I could be reading them wrong

Of course this will have to be after I figure out the angle I really like convexed!

I'm just a knife user. Use it, if it works, it works, if it don't, it don't.

Anybody holding me in high regard will get tired fast. I ain't no light weight.

The offer stands, and I'll be honest, I'm a little behind on my knife testing, soccer has been taking much of my time lately.

Moose

 

[parbajtor]

Can you recommend a good way to do this?

The feathersticks or inspecting the edge?

These days I need reading glasses and I have a pair of 3x magnification clip ons that I use.
A jewellers loupe or a fabric tester can also be useful. If you have good eyes, you should be able to angle the blade so the edge reflects light.
This will show any imperfections that you might have added during cutting.
It doesnt for me because the edge stays out of focus at that distance, hence the need for magnification. I still use the light reflecting off the edge.
It should be a very thin straight unbroken line (thinner than a hair). Chips will show as sparkles or a raggedy edge, rolls will show as a kink in the line. It's useful to know which part of the edge did the cutting to avoid having to inspect the entire length.

PS: I prefer convex because all you need in the field is a strop. Rehoning can be done at home, afterwards.

 

[Critikill]

I'm just a knife user. Use it, if it works, it works, if it don't, it don't.

Anybody holding me in high regard will get tired fast. I ain't no light weight.

The offer stands, and I'll be honest, I'm a little behind on my knife testing, soccer has been taking much of my time lately.

Moose

Lol. I appreciate it. Let me get my knife to where I want it, then we can figure out if you and/or I should do a write up on it, or if we should possibly find a trustworthy 3ed party to do it for us. Again, I'm pretty new on the forums so I don't know who would be trustworthy/capable of doing a good comparison between the different grinds on the BK16s.