PDA

View Full Version : What exactly is 70/30



turbochef422
11-17-2012, 08:37 PM
I know I can see that some blades are different but I don't exactly know what I'm looking at. My misono was different. I sharpen all of my knives 50/50 or the same to both sides and get them insanely sharp and I take pride in keeping sure sharp knives. But what is 70/30 or 60/40 and how do you maintain that. Is is more sharpening on one side or different angles and what are the benefits. Sorry if I'm boring with a basic question but maybe I'm missing out on something really cool. Thanks in advance. Nick

Crothcipt
11-17-2012, 08:41 PM
http://www.kitchenknifeforums.com/showthread.php/5656-Asymmetry-%E2%80%93-The-REAL-DEAL?p=93152&viewfull=1#post93152

here is a pic. in a great thread. You should read it, it explains many questions that pop up when trying to understand this. Not sure how to sharpen this way, but would love to learn.

eto
11-17-2012, 11:10 PM
I know I can see that some blades are different but I don't exactly know what I'm looking at. My misono was different. I sharpen all of my knives 50/50 or the same to both sides and get them insanely sharp and I take pride in keeping sure sharp knives. But what is 70/30 or 60/40 and how do you maintain that. Is is more sharpening on one side or different angles and what are the benefits. Sorry if I'm boring with a basic question but maybe I'm missing out on something really cool. Thanks in advance. Nick

You pretty much answered your own question. 70/30 - what have you 60-40 is basically the manufacture bevels they set.
You can change the bevel like you have been doing or keep it factory. If you want to maintain 70/30 ratio basically you sharpen the wider bevel (front side) at a lower angle , and sharpen the back side at a bit higher angle. Supposedly the purpose to these type of knives was to mimic a single edge , say yanagi knife, but to be more multi functional. There so thin to begin with I don't Think there is any true advantage here. Others may differ though.

Benuser
11-18-2012, 03:04 AM
The 70/30 edge of the Misono is a part of its overall geometry. Would you just put a 50/50 edge on it, after a few months you will have a crazy sharp knife that is perfectly unusable in the kitchen because of wedging and steering issues.
You may rebuild the entire blade to make it suitable for a 50/50 edge, but that is huge operation involving grinders no one will want to perform on a new knife.
You better stick with the original geometry and corresponding edge.
Just to give an idea: most Misonos will be fine with a 10-12 degree right bevel, 15 degree left bevel, where the right bevel is 2-3 times larger than the left one. With a brand new knife these figures are hard to see because Misono strongly convex their out of the box edges.

Benuser
11-18-2012, 03:18 AM
To me it isn't clear whether you asked for advice before applying a symmetric edge with the Misono, or you already did so, as one of the posters understood.
In the latter case: no real harm is done yet.
It is relatively easy to restore gradually the original configuration by only abrading from the right bevel, and only deburring / stropping the other side. So you will move the center of the edge back to its original position. Within a few sharpenings that will be done.

turbochef422
11-18-2012, 09:36 AM
The misono has been sharpened 50/50 for about 5 years. And now it's at a point where after thinning I still can't get it really sharp like I used to. It saw every day work for a few years and then here and there stuff after that. So I guess I'm asking about knives I'm gonna get. I try to follow the factory lines I just thought maybe there was a method behind it. Thanks for the answers.

chinacats
11-18-2012, 10:49 AM
Sounds like your current blade may just need a spa treatment...

turbochef422
11-18-2012, 10:52 AM
I mostly want to sharpen future blades the way they were intended. I get a knife real sharp. But like I read I can get a knife to shave my arm but I want it to cut well. I'm on Long Island and I'll check out korin but I need a class where I can see exactly what's going on an I need it before I go to the next level of knives. If anyone knows where there is such a thing please let me know. Thanks

Benuser
11-18-2012, 10:53 AM
I'm sure Dave Martell, Eamon Burke, Jon Broida or Korin's may save your Misono. For heavy thinning and other geometry changes both a grinder and a lot of experience are needed.

PS Sorry guys, hadn't seen the last posts!

zitangy
11-18-2012, 12:00 PM
One possibility is that the the blade has worn off and has receeded upwards (towards the spine) and thus is thick. Look at the choil area and compare the edge thickness to your otehr performing knives

Options
a) thin out the whole blade on sand paper, stone or a belt grinder. I do mine on sandpaper and thru the various grits, 240, 600 and 1000
b_ Thin out the edge and you need a lower angle as the edge by now shld be thick. Basically you need a bigger bevel

IN the final analysis, it's not the sharpening angle alone that determines the cutting performance.. the thiness of the edge does matter

Have fun and stay sharp..
rgds
D




The misono has been sharpened 50/50 for about 5 years. And now it's at a point where after thinning I still can't get it really sharp like I used to. It saw every day work for a few years and then here and there stuff after that. So I guess I'm asking about knives I'm gonna get. I try to follow the factory lines I just thought maybe there was a method behind it. Thanks for the answers.

bear1889
11-25-2012, 12:18 PM
I am left handed and this whole 70/30 thing confuses me, if I order a knife I can get a 30/70, which side is 30 and which side is 70.

Lets make this simple I want to slice and onion, I hold the knife in my left hand and the onion in my right.

Where is steep angle and shallow angle?

Is steep angle towards the onion and the shallow away from the onion as I hold the onion in my right hand??

eto
11-25-2012, 12:33 PM
I am left handed and this whole 70/30 thing confuses me, if I order a knife I can get a 30/70, which side is 30 and which side is 70.

Lets make this simple I want to slice and onion, I hold the knife in my left hand and the onion in my right.

Where is steep angle and shallow angle?

Is steep angle towards the onion and the shallow away from the onion as I hold the onion in my right hand??

If I understand you correctly, if this is the way the knife came from the manufacture and the bevels have not been change around for a left hander then you are correct.


the wider bevel will be towards the onion and the more narrow bevel will be away when the onion is held in your right hand.

tk59
11-25-2012, 12:37 PM
Larger bevel, smaller angle away from you as you're cutting on a board.

bear1889
11-25-2012, 12:43 PM
If I understand you correctly, if this is the way the knife came from the manufacture and the bevels have not been change around for a left hander then you are correct.


the wider bevel will be towards the onion and the more narrow bevel will be away when the onion is held in your right hand.

No the bevels have been changed for a left hander

eto
11-25-2012, 12:52 PM
No the bevels have been changed for a left hander

Then the wider bevel will be away from the onion the more narrow towards the onion when holding the onion in your right hand.

Im left handed to , I feel your pain, but its not to complicated as you may think. Hope this helps. Just think opposite with everything you learn when it comes to Japanese knives (Sort of Kidding).

Benuser
11-25-2012, 01:24 PM
Flat side with small bevel to the side of the food - to allow thin slices. Convex side with large, convex bevel should make food release easier.

bear1889
11-25-2012, 06:55 PM
thank you all

Notaskinnychef
11-26-2012, 03:24 AM
My carbonext is a 70/30, so this will be a test for me to sharpen in order to maintain that original split. I am worried that i will end up inadvertently moving towards a 50/50 as that is of course more natural to do while using the stones. Aside from just being conscious of my height on each side, any suggestive tips in order for me to maintain the original angles (or at least close?) maybe put two pennies on the one side and 3 pennies on the other to get a feel of the difference? I dont want to kill my blade lol

Benuser
11-26-2012, 06:32 AM
Start with thinning the right, convex, kanji side at the lowest angle you're comfortable with. Start somewhere a little above the shoulder, if any, and raise the spine to get towards the edge. Don't hesitate to remove eventually the original edge. Go on till you raise a burr on the left side.
Create a 10-12 degree bevel
on the right side, deburr the
left side at 15 degree with edge trailing strokes. Add a few edge leading strokes, and deburr the right side.
As the area behind the edge is very thin you don't have to worry too much about the angles.
Use the Magic Marker Trick to see where you're actually abrading steel. Good luck!

Von blewitt
11-26-2012, 06:49 AM
Start with thinning the right, convex, kanji side at the lowest angle you're comfortable with. Start somewhere a little above the shoulder, if any, and raise the spine to get towards the edge. Don't hesitate to remove eventually the original edge. Go on till you raise a burr on the left side.
Create a 10-12 degree bevel
on the right side, deburr the
left side at 15 degree with edge trailing strokes. Add a few edge leading strokes, and deburr the right side.
As the area behind the edge is very thin you don't have to worry too much about the angles.
Use the Magic Marker Trick to see where you're actually abrading steel. Good luck!

As I understand it the left bevel should be a smaller angle than the right ( for right handers) it appears smaller because the edge is not aligned with the centre of the spine but is 30% from the left/70% from the right

Benuser
11-26-2012, 07:03 AM
A smaller left angle angle is rather uncommon. A higher left angle will stabilize the edge greatly, recenter the edge a little, balance the friction somewhat and so limit steering, and hardly affect performance.

chinacats
11-26-2012, 11:17 AM
I thought I had a good grasp on this until trying to follow this thread...

:curse:

turbochef422
11-26-2012, 12:09 PM
Me too. I feel like I know what I'm doing till I read or ask questions.