more toothy thoughts

[Ken S]

As an old woodworker and newcomer to knives, the term "toothy" refering to edges is new to me. I don't ever recall it being applied to chisels or plane blades. 

I understand the concept of a toothy edge as it applies to cutting tomatoes with kitchen knives. I am not sure if it applies to everything cut with knives. Should knives always have toothy edges?

Ken

[grepper]

“Should knives always have toothy edges?”
 
IMHO I would say no.  Not all knives should have toothy edges, but many, or dare I say most, general purpose and kitchen knives benefit from a toothy edge.
 
Any knife used for slicing will generally benefit from a toothy edge because it helps to tear fibrous material and break the skin on things like tomatoes, broccoli stem, grapefruit skin, meat fibers, rope, cardboard and paper, etc.  Ever had a knife ride on the surface of something when you tried to cut it?  That’s exactly when a toothy edge will help.
 
Knives used for push cutting such as a cleaver or some vegetable chopping knives will not benefit from a toothy edge because they are not used for slicing.  The same is true for chisels, plane blades, gouges and pizza wheels, etc.  In those cases a polished edge and bevel is the way to go.
 
Of course this, like most things has some exceptions.  I’ve heard that chef’s cutting sashimi want a super sharp polished edge precisely because they want a perfectly smooth cut and can't tolerate even the micro abrasion caused by a toothy edge.  Really?  , but, OK,  I'll believe it.  
 
One year the weather was very bad for tomatoes all around the mid Michigan area.  It was strange.  The tomatoes had a tough, smooth skin but would not ripen.  Left to get ripe they basically rotted on the inside before they turned red.  It was weird, and most of the tomatoes were horrible to eat.  But, they were most excellent for testing knives!
 
I’d get big bowls of them and see what it took to cut them without mashing them.  Tough, smooth outer skin and soft mushy, almost rotten insides.  Very difficult to cut.
 
A extremely sharp, polished edge worked well.  The problem was the level of extreme sharpness was ephemeral at best.  Soon the blade dulled just enough and the blade would ride on the skin.  Apply more pressure to make the cut and it would squish the tomato. 
 
Lightly serrated blades worked too, as long as they were very sharp and not so serrated that they caused excessive lateral pressure on the tomato which would cause it to just tear and spill its guts on the cutting board.
 
What worked best was a sharp, toothy edge.  The best of both worlds. 
 
I would say that general use and most kitchen knives will perform best with some tooth to the edge the majority of the time.  Except for specific use blades I sharpen all my knives with a toothy edge. 
 
The next time you notice your blade riding on the surface of something you are trying to slice through, try a nice, toothy edge.  It might be just what you are looking for.   I little tooth can go a long way!

[Ken S]

Good thoughts, Grepper. We do have toothy blades in woodworking, too; we call them saws.

Ken

[Mark Reich]

Good thoughts grepper, and Ken, that cracked me up 

To share of my background, I have been using and sharpening woodworking tools for a few decades, and I have a lot of experience working with other professional finish carpenters, cabinet men and furniture makers.

I'm certain I've never heard a distinction of toothy edges among woodworkers. 

There is a big discrepancy though. It's a relatively new term I've only heard from internet sharpening forums, and more than a little ambiguous besides. 

Talking to normal people in knife related jobs, like we here from Max's trusted word, tooth is something like a clean 180 grit edge.

Talking with straight razor guys, you would be talking about tooth in grits from 16,000 grit to half a million.

Talking with knife guys is where This Forum has come up with much of the Total discussion! 

Talking to woodworkers, you would simply speak in grit designations, no mention of tooth.

In my estimation of woodworkers, many still use emery or AlO oil stones, and go to Arkansas oil stones after that. More advanced stuff usually means a good bench grinder, water stones/DMTs or a Tormek.

I used a bench grinder and DMTs until I got a 2x72, which was only several years ago. I still use waterstones, but I rarely go over 1K grit. 

The reason I don't refine an edge is because it's so short lived. Even with 3V chisels and A2 plane irons, I don't have time for refinement. If it shaves hair, it's definitely sharp enough to cut wood. I know a lot of oldtimers cut a bunch of wood with far less.

Just my two cents.

[wadebevan]

In the wood shop, I go with what works for planers and carving tools, a DMT or two, with a bit of strop to the burr.
I've found that careful attention to angle seems to be more relevant than the grit, but, that is just my limited experience.

My father passed on a worksharp that he had for lathe tools... Been a number of years, and I still haven't set it up.
I just grab my DMT's and a hard leather strop.

In the kitchen, for me, it depends on the knife and its use.  
For my scimitar (meat slicing scary knife), I go with more polish, meat should never be tough
My all purpose chef knives, I go a bit more toothy, as they are more of a push/pull action.
For the Nikiri, I have been going with a high polish, mostly because the action is straight up and down.
My girlfriend kinda freaked out last weekend because she brought her two favorite kitchen knives (both chef's knives) to me to sharpen.
When she was reaching for the serrated 'bread knife', I said 'use the one I just sharpened'.
After she looked at me like I was nuts, she used it and said 'oh my god!'.  Cut through a crusty loaf like butter.
It was a bit more on the toothy side.

Anyhow, my .02 on the subject.
And thanks for the pics on the subject Grepper!
Still learning lots from all you folks.
TW.

[grepper]

I’ve seen the term toothy edge mostly used in connection with kitchen knives.
 
I think the reason the term “toothy edge” does not come up in woodworking tool sharpening is because it is not applicable.  A toothy edge is not advantageous, and probably detrimental in push cutting applications like chisels, etc.
 
Same with straight razors.  The idea of shaving with a toothy edge blade is disturbing.
 
The same is more or less true for outdoor knives that might be used for hacking wood or beheading a fish.  Those are times where more pressure can be applied even if the blade is not at peak sharpness.
 
I think the term becomes most applicable with kitchen knives where a lot of force is generally not used.  The venerable slicing a tomato is a perfect example.  If you can’t break the skin, more force just smashes the tomato.  I very sharp, highly finished edge works OK, but as you say it sure does not last long.
 
I agree that about 180 grit makes a nice, toothy edge.  It works well for tomatoes and things like slicing rope, cardboard and anything that has fiber that can be torn by its micro-saw like edge.

[Ken S]

Interesting thoughts. A person and a term come to mind. 

The person is the late Leonard Lee, founder of Lee Valley and author of my favorite sharpening book. I never met him, but have always regarded him very highly. In his book and video, he discussed sharpening chisels with waterstones. He believed sharpening chisels to 4000 grit was more than adequate for most purposes.

The term is what the Adirondack guides used to call the wealthy gentlemen who came for a week's "roughing it". They called them "the sports". There is definitely a group of woodworking sharpening sports. They insist on every chisel being sharpened at least through the Shapton 30,000 stone, even if the chisel is used with framing lumber. (I can laugh because I have leanings this way.)

Interesting discussion.

Ken

[Bobbo]

Adirondacks! That's my old neck of the woods. I'm beginning to think that the 30,000 grit sharpening stone is on the same path as Adirondack guides and bamboo fly rods.

[Jeremy]

This is a subject that I've given a lot of thought in the past few years.
I worked with my step dad building hand hewn log homes using a broad axe, slick, chisels, etc., learning the value of a sharp tool. He taught me his way of using Japanese wet stones. He and I both had finer grits but agreed that 10k was generally where we both stopped. One very dissapointing thing in this era was spending a lunch break to, "just hone" the broad as a bit to take one swing and realize it's worse than before!
After the log cabin days I worked in food service for 12 years and always had the sharpest knife in the kitchen. My thick western chefs knife cut a tomatoe better than a new serrated knife.
So when I started my sharpening business I polished every bevel I sharpened until a couple years ago I tested the toothy theory at a butcher shop that I sharpen for, (national award winners) and found that the toothy edge they use with their boning, filet, and scimitars, (breaking knife) in there world, cut better initially and held its edge longer. Afterwards I continued to give every knife a nice polished edge and would separate the knives that where red meat or fish specific knives. Now for the past several months I've been trying less and less grit for all non fish knives, rather it be push or pull cut. The only thing I'm seeing so far is that it takes me less time to sharpen! Today I went with the lowest grit I've ever tried with a worn 120 belt and strop. My thought has been that with enough light you can see the edge being sharpened and not just the burr. A bright light will show the cloudiness of an edge that hasn't yet found its finest point. I still have a ton of questions and have budgeted a bess tester to answer many of the soon

[grepper]

That’s interesting Mr. Jeremy.  I’ve been sharpening for many years and like a lot of folks when I started out I learned that a polished, perfectly smooth edge created with a very fine grit abrasive was the way to.  What I have found however is that kind of edge dulls very quickly and, for example, starts riding on tomato skin very quickly.  A toothy edge however just keeps cutting.  If you search around, there are other studies out there demonstrating the same thing.
 
After years of sharpening I’ve now gravitated to really appreciating a nice, toothy edge.  For kitchen knives I’ll do 150-180 grit and have been very happy with the results. 
 
Without much effort I routinely get a 180 grit edge measuring around 150g sharpness with my PT50B.  That pretty much demonstrates that you can have a very sharp edge that is still nice and toothy.   Just what I like.  I only wonder, why did it take me so long?
 
Don’t know if you saw this thread or not:
http://bessex.com/forum/showthread.php?tid=68

In one of the replies Mr. Max the Knife, who sees and sharpens a LOT of knives said, "all i can tell you is the 150 grits after three weeks held up much nicer than the 600's ever did.......many of the 150 grit are still pretty sharp and useable............i like it"

Keep us posted on what you find too!