knife question for Stig

[Jimmy R Jørgensen]

I'm not saying overkill here. but as a noob and a person that "just" want good sharp kitchen knifes, this seems way overkill

I'm kinda getting that a knife can be to sharp to be good in normal use in kitchen, or am i getting it completely wrong?. I'm not in the game of operating on anyone so scalpel sharpness is not needed, but would be nice if there is a use for it.

[Rob]

well spotted...sometimes the lengths people go to on this forum are far beyond those necessary to achieve a simple, practical edge that works just fine for every day use....important safety tip when reading posts here :-)

[SharpenADullWitt]

You can get a knife too sharp.  In simplest terms, you get the two edges of the knife, to such a THIN point, that the edge disintegrates, while you use it.

There have been several posts on this, via trial by Tomato's (something that shouldn't really wear out a knifes edge).
http://forum.tormek.com/index.php?topic=1588.msg6595#msg6595

[Herman Trivilino]

The smaller the bevel angle, the weaker the edge, but assuming the steel can hold the edge, it's also the sharper the edge. Razor blades are made this way, but not kitchen knives. A kitchen knife is not a good instrument for shaving, and a razor blade is not a good instrument for preparing food. Used in a kitchen, a razor blade-like knife would quickly dull and have to be discarded as it can't be sharpened.

The other thing you often want in the edge on a kitchen knife is a "tooth", or a roughness to the edge. It makes the knife work more like a saw than a slicer. But in other applications, like for a sushi chef, a smoother edge is desired. The beauty of the Tormek is that with practice you can control all these variables and get the edge you desire.

[Jimmy R Jørgensen]

So Herman.

The ideal thing for me is the Tormek with the "normal" grindstone" ending with grid 1000 and honing it on the leather wheel. i'll get a good nice fihish but not a very polished one (Compared) but for the kind of work i'm talking about it is the ideal result, a good bevel with "teeth" that insn't to fine or week?.

[Herman Trivilino]

The ideal thing for me is the Tormek with the "normal" grindstone" ending with grid 1000 and honing it on the leather wheel. i'll get a good nice fihish but not a very polished one (Compared) but for the kind of work i'm talking about it is the ideal result, a good bevel with "teeth" that insn't to fine or week?.

If you carefully go through these steps you'll have a polished edge with a mirror finish that would make any sushi chef proud. Most critical is preparation of the grindstone in the fine 1000-grit state. You have to spend a lot of time on this step to get the surface of the grindstone feeling smooth as glass.

If you want more of a tooth you can use less care preparing the grindstone in the fine state.

You really need hands-on practice to learn this stuff. Going back and forth between the workshop and the kitchen, you can become a connoisseur of the edge.

[bobl]

Ken, while not answering your question to Stig and not trying to hijack this thread , I thought you might be interested in some testing I did cutting tomatoes with knives sharpened with more and less coarse abrasives, producing a more or less "toothy" edge.  As I recall, I had 4 or 5 knives sharpened ranging from right off the Tormek with a coarse stone, to very highly polished blades produced using 3M Microfinishing Film and super fine polishing abrasives to about 12,000 grit.

A couple of years ago we had a very hot, dry summer.  For whatever reason, it was not a good year for tomatoes.  They didn't ripen well, and would start to rot from the inside out, leaving a thin, smooth but tough skin, with very soft, watery, rotten guck in the middle.  Sounds delicious, doesn't it?

While they tasted like crap, they were excellent specimens for testing knife sharpness and edge grinds from rough to polished. 

The most excellent and telling subjects were tomatoes that were just starting to collapse, leaking rotten yuck, but were still more or less round without skin degradation.  When attempting to cut these stinking blobs, it took very little pressure to squish the tomato while trying to penetrate the skin with the knife.  So I picked up a bunch that were decomposing on the ground and proceeded to test.

What I found was that a polished edge can cut even a very soft in the middle, basically rotten tomato with a smooth, tough skin.  But..., it had to be really, really, sharp.  I emphasize; really, very sharp. Approaching razor blade sharpness.  I used a new safety razor blade for comparison.  If the knife was not super sharp, even with a careful sawing motion the blade would ride on the skin and the tomato would collapse and ooze out its insides before cutting the skin.  If however there was even a tiny break in the skin, the blade would slice most excellently.  These blades were so sharp, that even gently bumping against the finger would cause epidermal leaking.  They were most excellent at slicing human skin!  They would work great for sashimi or any other raw flesh, leaving a very clean cut.  I actually shaved with one and was surprised how well it worked. (Not recommended).

While the Tormek can produce knives that sharp, I found that degree of sharpness didn't last long with normal use.  As soon as the super sharpness was history, the polished blades became generally less useful.  The still performed well for chop cutting, but anything with a smooth surface became problematic.  It was evident even on vegetables like broccoli with a hard, smooth skin.

Without wishing to entertain the argument of longevity vs toothy/smooth edges, from my experience at least, a moderately toothy blade is generally more useful in the kitchen, and the edge lasts longer for all around, general, cutting.

I would be interested to know if anyone else has conducted the same tests, and how those results compare.

[bobl]

Stig,

I notice in your video with Stumpy and Mike a short scene where a chef's knife effortlessly slices a micro thin slice out of a tomato. The tomato is just sitting on a cutting board with no other support. That's pretty fancy shootin', partner.

I know that cutting things like tomatoes benefit from having a bit of tooth on the blade. Did you polish that blade on the leather honing wheel? Japanese wheel?

Ken

Ref this sharpness of blade  - from Bob The Knife Grinder.
Yes this sharpness is very impressive to the chef you have just left. However as you have said, the sharpness of this kind of edge does not last for long and is impossible for the chef to tickle up on his steel. First impressions are great, but longevity is short lived.
Standard sharpening on the T7 wheel supplied is more than good enough for chefs knives.
You will get happy chefs and repeat business with no quibbles.
Cheers.
Bob

[Elden]

Yes this sharpness is very impressive to the chef you have just left. However as you have said, the sharpness of this kind of edge does not last for long and is impossible for the chef to tickle up on his steel. First impressions are great, but longevity is short lived.
Standard sharpening on the T7 wheel supplied is more than good enough for chefs knives.
You will get happy chefs and repeat business with no quibbles.

Bob,

   What bevel angle do you use most commonly? I have seen mention of thinner bevel angles here on the forum. From your above stated perspective, are you using 15° or 20° bevel or do you take the time to match the existing bevel? Do you take time to do a double bevel?

   Your perspective on retension of sharpness is in accord with my thinking.

Thanks

[Elden]

Honing accomplishes two things; it removes the burr and abrades away or "polishes" out micro scratches on the cutting edge and the bevel. Check out the last two blade images here: http://forum.tormek.com/index.php?topic=1689.msg7998#msg7998 
That is the blade before and after honing with compound. The micro burr and scratching has been removed by the compound.

   Mark, I am not seeing your pictures.

[Ken S]

Eldon,

Whenever I think of "matching the bevel", usually a good idea, I wonder what the last guy was thinking. Somewhere in the past bevels there might have been a truly expert sharpener or a truly inexpert sharpener. Who knows???

Ken

[Herman Trivilino]

Look at the edge with a magnifier, Ken. You'll see clues about the level of expertise of the previous sharpeners.

[Elden]

Ken,

   If the bevel is like the one on my Buck hunting knife which I had hand honed throughout the years, a guided sharpening system showed a very inconsistent bevel. It had been sharp, just not consistent on the bevel. As I was the one who sharpened it, I can say the last guy was thinking about getting it sharp enough to field dress a deer or to butcher. It didn't have to be a perfect job to work. As it is now, the primary bevel is too acute to be a long lasting edge for hunting knife duty. I plan to put a fairly heavy secondary bevel on it.

[Ken S]

Good comments, guys.

Ken