Why secondary and micro bevels?

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bladsmth said:
If you resharpen a full convex grind the same way you made it the first time, it is the same blade geometry. I use the slack belt.
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I would say no way. If you don't thin the spine, when the edge is resharpened, the thickness measurement across the blade is bound to widen along the base of the edge, no matter where you take the measurement.

Explain your thinking, Fred
 
I think it comes down to ease of manufacture, maintenance, and slicing ability.

A secondary bevel is easier to maintain, repair, and manufacture.

Slicing ability is better with a thinner cross section.
You are pushing less metal through your object being cut, though friction plays a role too.

I always think of cheese.
A dull, thin flat ground knife is going to slice thin pieces of cheese better than a razor sharp Scandi.
 
BMK said:
Interesting:
[video=youtube;rKCT5wGV9xA]http://www.youtube.com/watch?v=rKCT5wGV9xA&feature=youtu.be[/video][/URL]
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Interesting is right.... interesting that he is working off of theory(poor theory) and not actual practical application. He is wrong about the angle of the edges all being the same. Yes, from the back of the spine to the absolute edge is the same for all three but the approach angle is different in each case. This is a classic example of booksmart vs. streetsmart. All the little nuances he thinks are so important really amount to jack-squat when used in the field. "My knife is 2 HRC points harder than yours, therefore, it will hold an edge longer." Not really.

That video was painful to watch... his building block grain structure is especially entertaining.:confused: We are all dumber for having watched that... just what I needed... thanks Monkeyman:grumpy::D:thumbup:


Rick
 
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That’s a good point Stacy, and I know it works. You can also hand hone the entire full convex blade (spine included) with a course stone, but both ways seem somewhat impractical if you’re out in the field and your blade needs re-sharpening. In that scenario, chances are they’ll all wind up with some degree of micro bevel, secondary bevel, modulated finishing angle or arch at the leading edge anyway… That’s been my experience.
 
not from a maker's perspective;
all my edges end up being convexed since I sharpen by hand, whether they start off as a perfectly flat machine ground bevel or as a slack belted convex. I simply do not have the control to keep the exact same angle every time I sharpen. Depends on what kind of day I'm having, the lighting or even the shoes I'm wearing. Varying the angle even 1/2 a degree makes a difference over time to a flat surface. The other thing is, I don't use a super aggressive hone to keep my blades sharp. I use a fine ceramic most of the time which removes very little material, but over time, polishes that edge bevel into a more rounded and less flat geometry. I have found that the angle increases over time, but that my knives also cut the kind of things they're made to cut better, even if I don't get them to shaving sharpness, and that's especially true for the big knives. I'll generally be more fastidious about the sharpness of the smaller knives, since they really more on cut to get thru something than brute force
 
Tai Goo said:
That’s a good point Stacy, and I know it works. You can also hand hone the entire full convex blade (spine included) with a course stone, but both ways seem somewhat impractical if you’re out in the field and your blade needs re-sharpening. In that scenario, chances are they’ll all wind up with some degree of micro bevel, secondary bevel, modulated finishing angle or arch at the leading edge anyway… That’s been my experience.
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If you grind along the spine this is reasonable thinking. But without narrowing the spine and shortening the blade a bit at each sharpening, I don't see how it is accomplished.

If the blade was continually sharpened in this manner the spine should disappear about time the blade is not worth sharpening anymore due to lack of material.

Are you doing any forging with this heat, Fred
 
Sharpening a blade is a lot like licking a lollipop,… any angle you go at it.
 
Rick Marchand said:
Asking which grind is better is like asking what the best tasting fruit is...

The answer is "beer", BTW.

Rick
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Hey Rick!

Out of all the guys on this thread,... I'm thinking, you would be the most fun to drink beer with. We need to make a point of doing that sometime! LOL

Cheers. :)
 
Tai Goo said:
Hey Rick!

Out of all the guys on this thread,... I'm thinking, you would be the most fun to drink beer with. We need to make a point of doing that sometime! LOL

Cheers. :)
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That may be true, but I would think the more relative question is; who on this thread has the most, and greatest beer. That, would be me. I brew my own and there are twelve cases in the brewery. I have awards?

What beer do you have Rick?:D



:thumbup: Fred
 
Rick,... since Fred has the most and the greatest beer on this thread,... let's meet over at his place!
 
This is the medium at my local pub. The large is twice the size. This is where that Apple engineer got so drunk he forgot his iphone prototype. :P
beer-1-2.jpg
 
Let's try beer as a new fast quenching medium for 1095! Hey!... if it doesn't work, you can always just drink it...

Seriously though,… every time we sharpen a blade through abrasion, we change the geometry a little,… even with a scandi,… In the long run, it gets narrower and narrower and eventually wears back to the point that it’s too flimsy to be any good, except maybe for a fish filet knife or to pick your teeth with. Scandi grinds on thin flat stock have the disadvantage of wearing away faster as opposed to some of the other types of grinds.

I like a hollow grind on straight razors.

Nice pic Carl!... kind of early in the day, but it's making me thirsty. :)
 
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I have 20 gallons of Applewine aging, 10 galons of mead, about 15 different country wines going, a few corny kegs of beer... 2 freezers full of aging beer and wine... 11% Belgian Dark Strong Ale in the fridge... I'm the best knifemaker. Hah.

I only drink a couple of beers a night usually so I had to chill on the brewing for now but I seriously have that many batches going right now.
 
I gotta get in on this. Once a year I brew up a batch of my special "Nacho Daddy" IPA that will knock you on your butt for a couple of days. It's fermenting as we speak!
 
Fred,
If you meanempiricallyy, then ,yes, you are correct.
However, if you mean practically, I think most folks would consider a change in blade geometry of a one hundredth of a percent or less as unaltered. You would have to carry the decimal out to four places to calculate the angular difference in any single sharpening. Even with the spine unchanged, in slack belt sharpening of a full convex grind, the edge geometry would be unchanged. By a laboratory standard, the geometry is changed every time the knife cuts something.
 
Daniel Fairly Knives said:
I have 20 gallons of Applewine aging, 10 galons of mead, about 15 different country wines going, a few corny kegs of beer... 2 freezers full of aging beer and wine... 11% Belgian Dark Strong Ale in the fridge... I'm the best knifemaker. Hah.

I only drink a couple of beers a night usually so I had to chill on the brewing for now but I seriously have that many batches going right now.
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Friendship request incoming:eek::D
 
bladsmth said:
Fred,
If you meanempiricallyy, then ,yes, you are correct.
However, if you mean practically, I think most folks would consider a change in blade geometry of a one hundredth of a percent or less as unaltered. You would have to carry the decimal out to four places to calculate the angular difference in any single sharpening. Even with the spine unchanged, in slack belt sharpening of a full convex grind, the edge geometry would be unchanged. By a laboratory standard, the geometry is changed every time the knife cuts something.
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Absolutely; I new what you meant I was just messing with you.:D

I spent a lot of years running long hand closures on surveys; I loved it when
they tallied 1 part in 30,000.

How are you holding up in the heat; wearing your kilt to forge in?
 
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