Need some help from the pros...

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Jason H
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Need some help from the pros...

Post by Jason H » Wed May 16, 2018 11:38 pm

I occasionally have this strange occurrence and I can’t detect a pattern. I get a certain “grinding” sound that turn the outer edges of my stones black. Interesting thing is that I have rounded the edges and the stone is flat. Any idea on what I am doing wrong? Here is a pic of my SG.

https://imgur.com/gallery/TANN8Wd

cedarhouse
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Re: Need some help from the pros...

Post by cedarhouse » Thu May 17, 2018 7:45 am

Have you lapped this stone? It could be that the stone is no longer flat and the edge of the knife is making contact on the edge and is spanning the middle like a bridge. The SG tend to stay flatter for longer than most stones but they still need to be kept flat.

The other most likely culprit is rocking the knife left to right and making contact on the edges. It could be as subtle too much pressure on one side or the other....the knife does not necessarily have to be "lifted up" for this to be an issue.


nevrknow
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Re: Need some help from the pros...

Post by nevrknow » Thu May 17, 2018 4:37 pm

Jason H wrote:
Wed May 16, 2018 11:38 pm
I occasionally have this strange occurrence and I can’t detect a pattern. I get a certain “grinding” sound that turn the outer edges of my stones black. Interesting thing is that I have rounded the edges and the stone is flat. Any idea on what I am doing wrong? Here is a pic of my SG.

https://imgur.com/gallery/TANN8Wd
Stone is flat or looks flat? Pencil grid it yet? Echoing the above ( correct answers ) :D

Radar53
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Re: Need some help from the pros...

Post by Radar53 » Thu May 17, 2018 6:53 pm

If the stone is flat then the "certain “grinding” sound" and the resulting marks on the edges of the stone indicate uneven pressure across the knife that rocks it ever so slightly to one side or the other.

It might be worth cleaning the stone up and start sharpening, just on one side for a while, until you hear that noise and see the stone marking. Note which side the stone marks, right or left, and this is the hand which is putting slightly more pressure on the knife. Change to the other side of the knife & repeat.

If this results in both sides of the stone becoming marked then it will tell you that it is related to the orientation of the knife on the stone. So it's either the hand holding the knife or the hand (fingers) on the blade itself, and you can adjust accordingly.

If the stone marks on the same side of the stone again then either your right hand OR you left hand is exerting more pressure regardless of whether it's holding the knife or putting pressure directly onto the blade. Again you can then adjust accordingly.

I hate that certain grinding sound!! :cry:
Cheers Grant

Just because you're not paranoid doesn't mean they're not going to get you!!

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Jeff B
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Re: Need some help from the pros...

Post by Jeff B » Thu May 17, 2018 7:16 pm

Ryan and Grant are all over this. :ugeek:
If God wanted me to be a vegetarian he wouldn't have made animals taste so good.

Jason H
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Re: Need some help from the pros...

Post by Jason H » Fri May 18, 2018 12:01 am

Thanks y’all. This one is a mystery. I flattened the SG and tried again with this old thin carbon blade. Very light pressure and immediately got that “grinding” on the the outer edge of the stone. I am at loss here.

https://imgur.com/gallery/pQlyMgM

cedarhouse
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Re: Need some help from the pros...

Post by cedarhouse » Fri May 18, 2018 12:21 am

Are you using sectional sharpening, where you work one section of the edge at a time, or sweeps, where you sweep through the full length of the edge on each pass?

The area on the lower right looks pretty good, the pronounced dark on the edge toward the top is a less ideal.

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Jeff B
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Re: Need some help from the pros...

Post by Jeff B » Fri May 18, 2018 12:29 am

Looks like your not keeping the pressure over the stone. Applying too much pressure using the handle or letting your hand that you have on the blade move off the edge of the stone causing the knife to tip to the edge of the stone. The hand on the blade should stay over the stone.
Last edited by Jeff B on Fri May 18, 2018 1:05 am, edited 1 time in total.
If God wanted me to be a vegetarian he wouldn't have made animals taste so good.

jmcnelly85
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Re: Need some help from the pros...

Post by jmcnelly85 » Fri May 18, 2018 1:04 am

Try putting the stone on a flat surface and put a level on it, it could be possible you have flattened at an angle.

Jason H
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Re: Need some help from the pros...

Post by Jason H » Fri May 18, 2018 9:28 am

I appreciate all the feedback here. So I tried two other knives on this SG and had no problems at all; the issue is with this blade. Yes, it is hard to manage because it is 10 inches, flexible, and has a wide sweeping curved tip. When I get home tonight l will have to put the same blade on a different stone to see what happens.

salemj
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Re: Need some help from the pros...

Post by salemj » Fri May 18, 2018 9:55 am

For what it is worth, I have to fight this kind of tendency all the time, and my stones also dish disproportionately out from the centre toward the edge in particular spots on each side. From just about every worn stone I've seen in any video (including Japanese masters), this is totally normal.

However, this also comes from where the primary point of contact is on the stone, AND, perhaps most importantly, where the point of acceleration is.

I find that I feel more or less "balanced" across the stone with different knives, too. I also find that sharpening in sections, making sure that one hand is directly over the centre of the stone, provides a clear sense of flat contact, regardless of how flexible the knife is, in part because it adjusts the point of acceleration and how it is achieved. In fact, I often make it a point to try to accelerate the stroke using my "control" hand rather than my "handle" hand—this makes a big difference, too.

For all of these reasons, trailing strokes also seem to wear differently: again, different point of acceleration, and different vector of acceleration, too (based on body movements).

I know it may sound weird, but since you've already gotten the good advice above about what is going on, I thought I might give you a more body-mechanical way of thinking about it. There's lots of talk about "consistency" in sharpening, but the fact of the matter is, there is NO WAY around the reality that sharpening involves a constant change in acceleration and vector of one object using another object (your body) that is not in alignment with the knife. With these kinds of mechanics, every single stroke introduces numerous changes in angle, pressure, and where the pressure/friction is maximally applied across the knife and stone, NONE of which can be avoided with freehand sharpening—they can only be minimized (it would be different if the motions were constant, but they are not...it is nearly impossible to accelerate/change the direction of one object using another without introducing all sorts of erratic forces). So, one way I've found of minimizing them is - again - to start by trying to focus on my "control" hand and having it directly above the stone, while using my "handle" hand as little as possible to accelerate or slow the stroke. It is mostly a mental exercises, but it does affect the physics on the stone face, at least for me!
~Joe

Comments: I'm short, a home cook, prefer lighter, thinner blades, and own mostly Konosukes but have used over a dozen brands.

jmcnelly85
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Re: Need some help from the pros...

Post by jmcnelly85 » Fri May 18, 2018 10:18 am

Long and flexible can be tough, I’ve found using as little pressure as possible to be the easiest way to go about sharpening to keep the flex from causing problems.

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Jeff B
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Re: Need some help from the pros...

Post by Jeff B » Fri May 18, 2018 12:42 pm

Long and flexible, that says a lot to me. I've had some of the same trouble your describing when it comes to long and flexible. For me it I found it came down to pressure control and pressure points. As been mentioned several times you need to keep the pressure point away from the edge of the stone which is more difficult with a more flexible knife. I think it's just a matter of adjusting/experimenting with pressure and practicing with different stroke styles.
You seem to have a solid base of knowledge, just take your time trying different things and you'll figure out what works.
If God wanted me to be a vegetarian he wouldn't have made animals taste so good.

gladius
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Re: Need some help from the pros...

Post by gladius » Fri May 18, 2018 12:54 pm

Jeff B wrote:
Fri May 18, 2018 12:42 pm
Long and flexible...it came down to pressure control and pressure points...keep the pressure point away from the edge of the stone
---
Agreed. Use a smaller portion of the stone and short strokes for more control.

Jason H
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Re: Need some help from the pros...

Post by Jason H » Sat May 19, 2018 12:34 am

I truly appreciate all of you who offered advice here, it is why I love this place so thank you. It is a thing of beauty to be able to ask a beginner question and receive so much thoughtful, reasoned, and explained advice from so many with so much experience.

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