Kitchen knives: Toothy edge vs Polished edge

[cbwx34]

My customers told me that "The knives dull too quickly" I thought about it and eventually came up with this idea.
...

One thing that has been left out of all this... (or maybe I just missed it)... who are your customers, and what type of knives are you sharpening?  A better description of what's going on... (volume of knives, how they're used, etc.)... might yield a better answer.

Mr. sharpco,  I agree with you on one point.  If a toothy edge is what you are going for, a 4,000 grit abrasive won't get you there and honing with compound will remove tooth.  The SJ will produce a beautiful polished edge.  Great for chisels and woodworking tools, but, at least in my humble experience, a toothy edge will last longer for things like cutting tomato skin.  With almost any amount of rolling of the edge, a polished edge will ride on the skin of a tomato, while a toothy edge will continue to break the skin. 

You know, play with it yourself.  Grind a toothy edge and carefully deburr so as not to remove the "toothy".  Grind a smooth edge and then compare how each cuts a tomato after chopping up some potatoes.  You may well arrive at a totally different conclusion that I suggest.  Nothing wrong with that!

I think the most important thing is to actually take the time to run the experiments yourself, and form your own conclusions based on your own findings.  If you don't do that, you are at the mercy of the opinions of others, and in the knife sharpening world that can be very confusing!

A microscope can be very informative.  If a blade just rides on the skin of a tomato, you can actually check out the edge and see why.  It won't answer all questions, but it's not a bad tool to have in your tool box. 

Your customers are providing you with valuable feedback.  You have a unique advantage insofar as your customers are running tests for you!  How cool is that?  Experiment with different edge finishes, bevel angles and the like and see what works.  That would be some real world, empirical data that most folks don't have access to.  Personally, I'd love to hear what you discover! 

Good point... by now, you should have enough info to try a few options... and see what will work best for your customers.

[Sharpco]

Mr. sharpco,  I agree with you on one point.  If a toothy edge is what you are going for, a 4,000 grit abrasive won't get you there and honing with compound will remove tooth.  The SJ will produce a beautiful polished edge.  Great for chisels and woodworking tools, but, at least in my humble experience, a toothy edge will last longer for things like cutting tomato skin.  With almost any amount of rolling of the edge, a polished edge will ride on the skin of a tomato, while a toothy edge will continue to break the skin. 

You know, play with it yourself.  Grind a toothy edge and carefully deburr so as not to remove the "toothy".  Grind a smooth edge and then compare how each cuts a tomato after chopping up some potatoes.  You may well arrive at a totally different conclusion that I suggest.  Nothing wrong with that!

I think the most important thing is to actually take the time to run the experiments yourself, and form your own conclusions based on your own findings.  If you don't do that, you are at the mercy of the opinions of others, and in the knife sharpening world that can be very confusing!

A microscope can be very informative.  If a blade just rides on the skin of a tomato, you can actually check out the edge and see why.  It won't answer all questions, but it's not a bad tool to have in your tool box. 

Your customers are providing you with valuable feedback.  You have a unique advantage insofar as your customers are running tests for you!  How cool is that?  Experiment with different edge finishes, bevel angles and the like and see what works.  That would be some real world, empirical data that most folks don't have access to.  Personally, I'd love to hear what you discover! 

Thank you for your advice.

In fact, today I am sharpening a knife and cutting tomatoes.

And I will buy a microscope. 

[Sharpco]

One thing that has been left out of all this... (or maybe I just missed it)... who are your customers, and what type of knives are you sharpening?  A better description of what's going on... (volume of knives, how they're used, etc.)... might yield a better answer.

Good point.

My main customers are restaurants, and many of them are butchers. Most of them don't use expensive knives. I often see knives similar to Victorinox chef knives.

[grepper]

What I have found, and this is just my personal experience, is that a freshly sharpened very sharp polished edge will melt through tomato skin.  But very quickly the edge rolls into a smooth rounded surface that rides on tomato skin while a toothy edge, because it rolls unevenly, continues to cut. 

In a previous post I attached an image of a rolled, polished edge.  It's not hard to see how it just slides on the smooth surface of a tomato.  A toothy edge maintains its "bite" longer and is able to break the skin.  It acts like a serrated edge only on a microscopic level.

I became so frustrated with ever so slightly dull polished edges riding on various surfaces like tomatoes, plastic twine and other similar surfaces that I started experimenting with toothy edges.  The difference was literally amazing. 

I used a sharpness tester when doing the tests.  The polished edges were very sharp as were the toothy edges so it was not that the polished edges were dull to start with.  The super sharp polished edges cut everything very well.  They just didn't maintain that cutting ability.  After only a short time that frustrating riding on the surface of stuff started while the toothy edges continued to cut.  If I were to guess, that's what your customers are whining about.

That said, a chisel or a gouge needs a polished edge for push cutting.  Toothy edges are great for food slicing and polished edges a good for push cutting.  Of course there are exceptions, like sushi chefs want a polished edge, but in general, I've had much better results with toothy edges for slicing.

Like I mentioned before, your results may be different than mine.  What's cool is that you have the opportunity to do extensive real world testing which is something I don't. 

I posted this link before, but it might be worth posting it again because it's exactly what you are doing:
http://bessex.com/forum/showthread.php?tid=68&pid=614#pid614

I'll be most interested in what you find out!

[Sharpco]

What I have found, and this is just my personal experience, is that a freshly sharpened very sharp polished edge will melt through tomato skin.  But very quickly the edge rolls into a smooth rounded surface that rides on tomato skin while a toothy edge, because it rolls unevenly, continues to cut. 

In a previous post I attached an image of a rolled, polished edge.  It's not hard to see how it just slides on the smooth surface of a tomato.  A toothy edge maintains its "bite" longer and is able to break the skin.  It acts like a serrated edge only on a microscopic level.

I became so frustrated with ever so slightly dull polished edges riding on various surfaces like tomatoes, plastic twine and other similar surfaces that I started experimenting with toothy edges.  The difference was literally amazing. 

I used a sharpness tester when doing the tests.  The polished edges were very sharp as were the toothy edges so it was not that the polished edges were dull to start with.  The super sharp polished edges cut everything very well.  They just didn't maintain that cutting ability.  After only a short time that frustrating riding on the surface of stuff started while the toothy edges continued to cut.  If I were to guess, that's what your customers are whining about.

That said, a chisel or a gouge needs a polished edge for push cutting.  Toothy edges are great for food slicing and polished edges a good for push cutting.  Of course there are exceptions, like sushi chefs want a polished edge, but in general, I've had much better results with toothy edges for slicing.

Like I mentioned before, your results may be different than mine.  What's cool is that you have the opportunity to do extensive real world testing which is something I don't. 

I posted this link before, but it might be worth posting it again because it's exactly what you are doing:
http://bessex.com/forum/showthread.php?tid=68&pid=614#pid614

I'll be most interested in what you find out!

It's amazing! 150 grit is coarser even than Tormek's 220 grit.

[cbwx34]

What I have found, and this is just my personal experience, is that a freshly sharpened very sharp polished edge will melt through tomato skin.  But very quickly the edge rolls into a smooth rounded surface that rides on tomato skin while a toothy edge, because it rolls unevenly, continues to cut. 

In a previous post I attached an image of a rolled, polished edge.  It's not hard to see how it just slides on the smooth surface of a tomato.  A toothy edge maintains its "bite" longer and is able to break the skin.  It acts like a serrated edge only on a microscopic level.

I became so frustrated with ever so slightly dull polished edges riding on various surfaces like tomatoes, plastic twine and other similar surfaces that I started experimenting with toothy edges.  The difference was literally amazing. 

I used a sharpness tester when doing the tests.  The polished edges were very sharp as were the toothy edges so it was not that the polished edges were dull to start with.  The super sharp polished edges cut everything very well.  They just didn't maintain that cutting ability.  After only a short time that frustrating riding on the surface of stuff started while the toothy edges continued to cut.  If I were to guess, that's what your customers are whining about.

That said, a chisel or a gouge needs a polished edge for push cutting.  Toothy edges are great for food slicing and polished edges a good for push cutting.  Of course there are exceptions, like sushi chefs want a polished edge, but in general, I've had much better results with toothy edges for slicing.

Like I mentioned before, your results may be different than mine.  What's cool is that you have the opportunity to do extensive real world testing which is something I don't. 

I posted this link before, but it might be worth posting it again because it's exactly what you are doing:
http://bessex.com/forum/showthread.php?tid=68&pid=614#pid614

I'll be most interested in what you find out!

I add bold to a part that maybe we're overlooking... what is causing your edges to so "quickly roll"?

[Jan]

My main customers are restaurants, and many of them are butchers. Most of them don't use expensive knives. I often see knives similar to Victorinox chef knives.

Victorinox chef's knives are made of very good steel which can be hardened up to 56 HRC. Such a steel can be sharpened to bevel angle 15° (30° included angle) for slicing knives, and to bevel angle 20° (40° included angle) for boning knives.

After many sharpening cycles the blade can become too thick and the knife does not perform well even though it was freshly sharpened and correctly deburred. The blade has to be thinned. In my opinion the Victorinox chef's knives cannot be efficiently thinned on Tormek.

Not each steel is as good as the above mentioned x50CrMoV15. When the steel is softer, than the edge will dull more rapidly, and it is not recommendable to sharpen the chef's knife to a thin 15°.

When I am in doubts about steel hardness I use an inexpensive hardness testing file set. One almost invisible scratch with the 55 HRC file will tell you whether you can sharpen the 15° bevel angle or rather a larger one.

Jan

[SharpenADullWitt]

x50CrMoV15 is in a classification as German steel.  That label has to meet certain criteria and be put ON the blades by their laws.  I do wish all steels had to be marked that way, as it would be easier to learn ones preferences.  I have found the Victorinox and Update international ones that use this type of steel, seem harder and take longer to sharpen, then my personal favorite, the Dexter Russel sani-safe. (only labeled as high carbon steel)
Both work well at 15° though.

How about a name on that tester?

[Jan]

My test set is similar to https://www.amazon.com/Grizzly-T10277-Piece-Hardness-Tester/dp/B006SJF7UK/ref=cm_cr_arp_d_product_top?ie=UTF8

Jan

[grepper]

Mr. cbwx34 queried,  "I add bold to a part that maybe we're overlooking... what is causing your edges to so "quickly roll"?"

Hardness of the steel, cutting board impact, toughness of material being cut and bevel angle all contribute to edge dulling.  Sharper edges tend to roll more easily simply because they are thinner.  I know, a sharper edge will cut more easily and therefore less pressure is applied to the edge which causes it to dull less easily. 

The point is that there is a happy medium when steel hardness, bevel angle and how the blade is going to be used is all considered.  I know that in industrial settings they have found that for some types of blades an initial sharpness reading of 400 or more is most effective in the long run. So it varies.

Finding that perfect balance is the tricky part.

[Sharpco]

After many sharpening cycles the blade can become too thick and the knife does not perform well even though it was freshly sharpened and correctly deburred. The blade has to be thinned. In my opinion the Victorinox chef's knives cannot be efficiently thinned on Tormek.

How do you do when you need to make a knife like Victorinox thin?

[Stickan]

Hi,
Since the question about thinning a blade was asked I have talked to some manufactures and sharpening business that I know, about how often this is actually done and when it's necessary.

To start with, our machines are not very suitable to thinning a knife blade. It not designed that way from the start and was not intended to actually do that. To thin a knifeblade you need a flat beltgrinder or similar, simply said, a larger flat grinding-system.

With this said, the answers I got was as I predicted, this is not common service and it will also change the knifes original design and choice of material it was made in.
A larger professional sharpening business will have machines that makes this possible but the time used doing this service and the charge for the sharpening cost is not in level.

Best,
Stig

[cbwx34]

Hi,
Since the question about thinning a blade was asked I have talked to some manufactures and sharpening business that I know, about how often this is actually done and when it's necessary.

To start with, our machines are not very suitable to thinning a knife blade. It not designed that way from the start and was not intended to actually do that. To thin a knifeblade you need a flat beltgrinder or similar, simply said, a larger flat grinding-system.

With this said, the answers I got was as I predicted, this is not common service and it will also change the knifes original design and choice of material it was made in.
A larger professional sharpening business will have machines that makes this possible but the time used doing this service and the charge for the sharpening cost is not in level.

Best,
Stig

Actually, I think I predicted the answer you would get.     (This also links to the original thread on the subject).  Hopefully, you will continue to pursue the topic.

[cbwx34]

After many sharpening cycles the blade can become too thick and the knife does not perform well even though it was freshly sharpened and correctly deburred. The blade has to be thinned. In my opinion the Victorinox chef's knives cannot be efficiently thinned on Tormek.

How do you do when you need to make a knife like Victorinox thin?

I mentioned one way to tell if a blade needs thinning, or at least thinning behind the edge, in the other thread on the subject...

One quick way of checking to see if a knife needs thinning is to lightly pinch the blade above the sharpened bevel, and slowly drag your fingers down over the bevel and off the edge.  If you feel a 'bump' as you go over the bevel... the majority of the time, thinning (at least behind the edge), will improve cutting performance.

[Jan]

After many sharpening cycles the blade can become too thick and the knife does not perform well even though it was freshly sharpened and correctly deburred. The blade has to be thinned. In my opinion the Victorinox chef's knives cannot be efficiently thinned on Tormek.

How do you do when you need to make a knife like Victorinox thin?

Sharpco, I do not have personal experience with knife thinning.

Here is a Steve B. answer from previous thread: 

My personal solution for thinning is to take the knife to the local wet grinding service that serves the restaurants and have them hollow grind it. Their work is not pretty but is functional.  $2 for a stamped knife and $5 for a forged knife of any size.