Some notes for asymmetric angles

[Leo Barr]

The reason the blades have an asymmetric grind is that the bevel offset from what would be imagined as the centre of the blade the diagrams that KnifeKnerdAtx posted show how it works plus these blades are usually sharpened freehand and the say 70/30 relate to the bevel ratios . The idea of the asymmetric blade is to minimalise flesh damage when cutting.

[Leo Barr]

hopefully this ref pdf is readable now still cannot get pdf to upload have reduced it to 1.3 mb

[Gerald Welsby]

Leo,
I tried to post something similar yesterday but it disappeared!
if the ratios refer to bevel widths, not angles then without specifying an edge offset from the centre of the blade then the 70:30, 60:40 etc. are meaningless. Taking as an example the 30 degree included angle and bevel ratio of 60:40, (I think!) I can sharpen at angles 5:25 and 25:5 and still meet the criteria. I still think the ratio applies to angles!
All the best,
Gerald.

[Leo Barr]

It is a rather confusing subject but things to remember is that most Japanese knives are hand finished (final sharpening) so there is no reference to angles it is the ratios that are important .
If you get hold of a true asymmetric ground knife it will become more clear to picture.
It is possible to over complicate this with mathematics angle cubes etc one must remember that most blade smiths do not have much more than rudimentary maths and certainly do not use angle cubes therefore in general the ratios refer to the grind offset since one side of the knife will be much flatter than the other. There are many articles on this on the net I think the answer is to keep it simple look at the diagrams and think of what the average Japanese blade smith uses to make a knife.

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[Gerald Welsby]

Leo,
firstly, many thanks for taking the time to put the demonstration together. I know that you do these things by hand. We mortals 🙂 however, must trust to our WE’s to do the job, so must use angles rather than bevel ratios. In fact, just do this thought experiment. Draw a line, length 3 units and attach another line, length 2 units at the end, at 30 degrees. Superimpose this on a magnified end-on profile of your knife. You’ll see that with rotation and scaling you can put the edge virtually anywhere on the width of the knife.
Using angles of 18 and 12 degrees does not get me out of the woods either – the same applies. However, looking at your diagram the edge remains in the centre of the blade. In this case the bevel ratio is near as damn it 1.5 to 1. I’m sure that if my brain were not fried and I could do the trig your angles would come out as near as damn it 18 and 12 degrees 🙂
Clay, if you’re reading this, is there an approved technique for creating asymmetric knives? Searching on “asymmetric” reveals 0 results, of course!
Thanks again, Leo.
Gerald.

[Leo Barr]

Gerald

Perhaps your question how to create an asymmetric blade will help clarify it for you.
Let us suppose that you have a fairly thick knife from spine to edge so that there is very little taper through spine to edge this would make a good candidate to make an asymmetric from so assuming you are right handed you woululd thin the right side of the knife that is looking down from the spine so in other words you would increase the angle clockwise (looking down from the spine) from the spine to the edge creating more of a wedge profile (it does not have to come from as high as the spine and sometimes this will be slightly convex in shape) once you have done this enough there will be a visible difference between the sides . This will also in all probability remove the bevel on the left hand side.
Now you can put an asymmetric set of bevels on the edges . Now the point that goes grey for me is this thinning angle that has been put on the right side as compared to the left for instance an 80/20 asymmetric does not look like a chisel from spine to bevel on the right side but does have a lower bevel on the right there for a wider bevel on the right and a much smaller one on the left.
So this is as much as I understand at the moment which is why when I get an asymmetric to do I find out from the web what the correct values are.
I think the whole point of the asymmetric is to do less damage to food I posted elsewhere on this site about that but to recap the less the flesh of fruit is bruised or damaged in cutting the better the flavour(the umami-the spirit flavour energy of fresh food) the main body of the food been cut is not compressed much because the blade in contact is virtually flat; the slopped side pushes the cut food away .

The knife shown is a Masahiro Honyaki 80/20 boning knife all the knives in this range are asymmetric this is what the Japanese makers call a Western knife the traditional knives are more asymmetric like a Deba or a Yanagi .
I hope this helps a little

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[Pat]

I will suggest that if you do not already, get some decent lighting for your area you use the WE at. I have been working an MSC PT with asym bevels (not asym grind, but only the bevels are asym/chisel) and last night rounded the tip something good and overall am displeased with my results where I normally have fantastic results on dual bevel blades.

I didn’t have good lighting and rounded the tip something nasty so had to reset that. Also, the up and down strokes, at least for me, only work well for reprofiling, but when actually moving up in grits, heel to tip strokes, whether up or down, get the edge useful.

What I find is that you have to be very deliberate when reprofiling to get at the apex over the ENTIRE EDGE, INCLUDING THE TIP AT THE VERY END OF THE TIP, else, you will be disappointed when using the tip vs the belly or heel of the edge.

I am sure you all have learned this already, but I am still in kindergarten related to this operation.

Would be great to see a video of someone sharpening an asym beveled edge and what they do afterward to remove the burr, then strop.

[Leo Barr]

PLEASE DISREGARD EVERYTHING I HAVE WRITTEN IN THIS SUBJECT INCLUDING THE TABLE OF ANGLES I BASED THE INFORMATION ON WHAT SOME PEOPLE HAD WRITTEN ON THE NET WHICH WAS MISLEADING .
USE THE SAME BEVEL ANGLES THE ASYMMETRIC GRIND WILL MAINTAIN THE ASYMMETRIC RATIO.
IF YOU SHARPEN IT CORRECTLY THE BEVEL RATIOS WILL BE DIFFERENT BIGGER ON THE MORE SLOPED SIDE & SMALLER ON THE FLATTER SIDE.

[Pat]

IF YOU SHARPEN IT CORRECTLY THE BEVEL RATIOS WILL BE DIFFERENT BIGGER ON THE MORE SLOPED SIDE & SMALLER ON THE FLATTER SIDE.

Agreed.

[Author]

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