Blade geometry question.

M

modernbeast

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Jul 18, 2015
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I want to ask about a specific knife but I know I can't so...

The kitchen knife in question is made from ASU-8 high carbon stainless with a rockwell of 58/59 and has a 15 degree 50/50 symetrical edge.

I am sure that means something to some of you but mostly I am just copying the text.

I think a sharper angle means sharper but sharpening more often and higher hardness means better angles can be accheived but it is more susceptible to chipping.

My question is will this be signifigantly harder to sharpen than a 25 degree knife(for a rookie). I think the symtry deal means both side need to ne done evenly, is that correct?

And how hard is is to chip a high hardness knife?
 
Once the edge bevel is established, you should notice no real difference between sharpening at 15 and 25 degrees. Thinner edges actually tend to hold their edge longer (or at least feel like they stay sharper longer) than a thicker one, the lower angle of 15 degrees should yield a thinner edge.

Taking a step back, an AUS-8 blade at 58-59 is not really that hard to begin with, and can be sharpened easily especially with the right stones. As far as chipping, AUS-8 is pretty tough stuff and run at the given hardness, shouldn't be a problem.
 
"I think a sharper angle means sharper but sharpening more often and higher hardness means better angles can be accheived but it is more susceptible to chipping."

Not really, the width of the apex determines sharpness. With something like AUS-8 15 degrees is pretty appropriate. Chipping isn't a byproduct of being thin, it's a byproduct of being too hard without adequate toughness for a given task.

"My question is will this be signifigantly harder to sharpen than a 25 degree knife(for a rookie). I think the symtry deal means both side need to ne done evenly, is that correct?"

50/50 just means the edge is a true V instead of something like 60/40 where the edge is offset a little. AUS8 shouldn't be very difficult to sharpen. Pretty much any knife made of decent steel sharpens the same, some take longer than others. AUS8 isn't very wear resistant compared to some steels while being more wear resistant than others. A rookie shouldn't be scared of it. I am far away from being an expert and have dealt with much higher hardness and higher wear resistant steels. I haven't fallen over from a heart attack yet.

"And how hard is is to chip a high hardness knife?"
58-59 isn't that hard but it really just depends on how it was hardened and if the maker did it right. There are axes out there at the same hardness and there are knives that are softer and there are knives much harder. 58-59 rc is pretty normal though.
 
AUS-8 is a medium quality stainless steel.

The 58-59 Rc is the hardness of the steel at that temper. Most knives range from the mid 50s to the mid 60s in terms of hardness.

The 15 degrees per side (30 degrees inclusive) is moderately acute, but nothing too acute, especially for a kitchen knife. I'd guess that most people here sharpen their EDC knives at 20 dps. Less than 15 dps gets into acute territory where you need to know what your doing. You shouldn't have trouble with your knife chipping.

The things that affect sharpening are the steel alloy (high-wear resistant steels with lots of hard carbides like vanadium are the most difficult), the hardness of the steel (you're kind of in the middle) and the width of the edge shoulders (narrower is better).

Basically, your knife should be easy to keep sharp. I'd keep the same 15 dps angle. If you do experience chipping, you can add a microbevel of 20 dps.
 
I totally agree with Knifebro.

Maybe practice sharpening on a junk knife before going for the nice one.
Don't be bashful about using a sharpening jig you can set the angle on either.
One thing, changing from a shallow angle, say 15°, to a wider angle e.g., 25° is fast and easy
but
changing back to the shallower angle takes more time and effort. I'd be sure you can't make the 15° work for you before going wider.
I love thin edges with shallow angles . . . but I would never try to chop through a small bone or other hard thing with a delicate edge geometry. That is one reason to have more than one of the larger kitchen knives.
 
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Hey thanks for all the info. From the sound of it this is more intermediary rather than advanced knife, probably a good fit.

For the record I try to avoid cutting bone but read some nasty stuff about chipping. I am glad this steel is decently tough.

I think, thanks to your help, I can go ahead and pledge.
Thanks.
 
I wouldn't worry about chipping--especially not at that angles and (presumably a gyuto cross section rather than a nakiri) the grind of the knife.

I use a 63 - 65 HRC Blue #1 nakiri with a ~8 degree per side edge. It is so resistant to chips that I got over-confident and used it to break down a turkey last Thanksgiving. It took pounding the edge through some small leg bones to actually get it to chip.
 
I was thinking this knife is more a cross between a gyuto and a Wüsthof. Then after looking again (and googling cross sections) I realize your not talking about the knife shape but the blade it self.

What's the difference between the gyuto and the nakiri blades? When is one preferable to the other?
 
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