Uneven Bevel == Slightly Warped Blade?

S

Shamshir

Joined
Mar 19, 2015
Messages
22
Hello,

I sometimes see this when sharpening some knives. At one section, the bevel is wider. I immediately think that I had wobbled. But, when I look at the opposite side of the blade, that section is actually narrower. Please notice my fantastic diagram showing the (exaggerated) uneven sections.

So, am I doing something wrong in how I go about this? Or is it minor deformations in the blade that cause this?

Thanks in advance,
Shahriar.

46454062405_88a996275e_k.jpg
 
Warp is common. In fact, I'm finding it pretty rare when there actually isn't any noticeable warp, bend, kink or waviness in a knife blade. It's usually AFTER I notice such unevenness in the bevels, that I then notice some bend or warp, looking down the length of the blade from the heel end, with the edge UP and the tip pointed away from me. Then it just seems too obvious, all of a sudden...

In some blades, it's even easy to see which ones were shaped or finished on belt grinders, with visible parallel-sided depressions in the primary grind, running perpendicular to the spine and matching the width of commonly-used grinder belts. All kinds of ways for the finished blade to be asymmetrical in some fashion.
 
Obsessed with Edges said:
Warp is common. In fact, I'm finding it pretty rare when there actually isn't any noticeable warp, bend, kink or waviness in a knife blade. It's usually AFTER I notice such unevenness in the bevels, that I then notice some bend or warp, looking down the length of the blade from the heel end, with the edge UP and the tip pointed away from me. Then it just seems too obvious, all of a sudden...

In some blades, it's even easy to see which ones were shaped or finished on belt grinders, with visible parallel-sided depressions in the primary grind, running perpendicular to the spine and matching the width of commonly-used grinder belts. All kinds of ways for the finished blade to be asymmetrical in some fashion.
Click to expand...
I noticed on my ZT 0393 when closed, the middle of the blade is closer to one side of the scale but then the tip is centered.
 
When I got home I looked again at the blade. Yeah, I can see a slight "wave". But it's so slight it's hard to trust what I see... could be some sort of reverse placebo.
 
When my technique was worse, I would inadvertently sharpen flat while it should follow the curve of the belly. It resulted in wider bevel. This was before I really pay attention to lifting the handle ( HeavyHanded HeavyHanded technique) or follow the curve of the belly. Imagine a straight line across the face / primary bevel from middle of straight portions to middle of belly curvature. It happens on my right hand side but not on my left.

Most likely the issue that blade is warped prevails, but in rare cases it’s the technique. How do I know? More than one knife has this, so it must be me. :o
 
I've also created some issues on my own, with too much pressure exerted on blades that flex easily, and spending too much time grinding a small portion of the bevel, resulting in flat-spotting portions of what should be a more curved or 'bellied' profile. These issues will also be magnified by any blade grind/warp issues present.
 
Shamshir said:
When I got home I looked again at the blade. Yeah, I can see a slight "wave". But it's so slight it's hard to trust what I see... could be some sort of reverse placebo.
Click to expand...


Nearly all blades have some amount of warping, and it only becomes more and more obvious the more precise your angle control becomes.

Some knives do not have any visible warpage but most do. This hearkens back to the Murray Carter method that begins with a comprehensive visual inspection. I should do this every time, but these days I just assume the blade is warped from the get go and where/how much will become obvious as I work.

Many factory grinds have this hidden to some extent as they have been sharpened on relatively narrow belts or wheels, once you put it to a stone you'll see all.
 
When I use a guided system I try to use the narrowest stone I have. my Kansbol has a very pronounced warp and I use 15-20 mm wide stones to mitigate the problem. It's slower to do the job and while not perfect, I get more even bevels.
 
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