Blade size: 5 mm x 35 mm. A very small knife.
This is a crude of a proof of concept, made from cutting a small strip of metal from a can of Del Monte Cut Golden Wax Beans. I just bent the strip in half, slipped it over the tang of the blade and clamped in in the small knife jig. Very sturdy. Stronger than you would probably think.
Much to my surprise, it worked perfectly the first time, putting a 20 degree bevel on the tiny blade, without interference from the small knife jig. Clamping to the tang keeps the blade centered in the jig. Only used for grinding with the wheel, but then, on very small knives that's what you do anyway.
I think about three sizes would handle all knives too small to fit in the standard jig. Obviously the design and construction material could stand some refinement. :)
Once made, it's slip it over the knife, clamp in jig. Done. (Bob's your uncle). You get all the advantages of using the small knife jig.
(http://tinyurl.com/a8p2cht)
What I dont understand about pocket knives like that is why you dont just freehand them? I appreciate free handing isn't easy due to it being difficult to avoid tipping the angle and ending up with a multi faceted bevel. But of all the knives, small bladed ones offer the most control to avoid that happening. Two fingers placed one at either end of the blade is enough to prevent it rocking given they're so short.
I wonder have you tried free handing it or jumped straight to the improvised jig?
Based on the unsteadiness of longer (chefs) knives I could understand some reticence to free handing, with those tiny blades though, it really isn't difficult and its worth persevering to develop the skill
Nice jig, grepper. I can't wait to try it out.
Rob, for me freehanding gives me inconsistent results. I'm looking for something better.
I agree its dang hard to get a consistent bevel on a long chefs or cooks knife but I really can't see the problem with what we call pen knives. I mean half of them have their blade length only twice the width or so of the grindstone. They're by far the easiest blade to control a consistent angle (grinding away from you)
I guess my point is that are people letting the fear of inconsistent bevel problems deter them from really developing the technique (when those problems are more justified on longer knives)
I'm sure as hell no expert and yet find it pretty simple to grind small knives. I do freehand long knives too and I'm not bad at them but controlling a single facet bevel on them is substantially more difficult
Rob,
Why not freehand? I'm not afraid of it or anything, I'm not very good at it. I can get it sharp, I'm just very slow... Could I get better? Sure! Would it be cool to do well? Absolutely! Could I relax and watch TV with my little stone and practice? Yupper! I'm in complete agreement with everything you said.
But... I just got a razor sharp edge very quickly with the T-7. With a little knife it takes almost no time at all, just as if the small knife jig worked out of the box for tiny blades.
Am I an uncoordinated goof for not bothering to improve at free handing? Uh. Huh. :'(
Does the little jig add-on get tiny knives really sharp, really fast? Yup. :)
Herman,
I'd be interested in you input when and if you try one. Next round I'm going to make a cutout where the spine meets the handle so that the add-on can sit perpendicular to the blade. I'm sure there are lots of fun issues to find and resolve.
What was cool and promising about it was that a rather lame first attempt with a little chunk of bean can worked so well.
Herman,
Might save just a little messing around...
With this incarnation of the thing, having the knife handle rest against the jig is what gives the knife stability. Not to say this couldn't be overcome with design/material, but the little bent piece of scrap metal cannot grip the tang enough to stop the knife from rocking.
What's most interesting about this is that there is really no additional setup time. Just slip it over the blade and clamp it down. Only a few seconds longer than just using the small knife jig.
Quote from: Rob on March 11, 2013, 01:39:06 AM
I agree its dang hard to get a consistent bevel on a long chefs or cooks knife but I really can't see the problem with what we call pen knives. I mean half of them have their blade length only twice the width or so of the grindstone. They're by far the easiest blade to control a consistent angle (grinding away from you)
When I remove the knife from the grindstone to examine it, and then find that I have to return it to the grindstone for further grinding, I can't get the same angle as I had the first time. That's my problem, inconsistency.
With a softer steel it's easier because I can grind until I see the bur begin to appear. But with harder steels I can't do that because no bur ever appears. And it can't be felt, either!
Bail on the burr! Just keep turning the knife often keeping an even bevel.
Until the knife blade has been ground to nothing?!
Seriously, how do you know when to stop grinding?
The nicest pocket knife I own is a Buck 066. Bought it about 5 years ago, it has no nicks in it and it has never been sharpened. It now needs to be sharpened and I want to do it by removing as little steel as possible.
I've carefully measured the edge angle to be 40º, thus the bevel angle is 20º. I've also determined by careful measurements that the side of the blade makes an angle of 2º with the center line of the knife. Therefore the bottom of the knife needs to make an angle of 18º with the surface of the grindstone. That's the angle I set the platform on my newly invented jig.
Hopefully the knife will become sharp long before you turn it into a toothpick!
I'm no knife sharpening guru or anything, so I'm just guessing. Does it not stand to reason that if you remove metal from one side at particular angle, and then do the same on the other side, that the knife will become sharp? The scanning electon microcope tests that were linked to here a couple of times clearly show that a wire edge and burr forms probably long before you could see or feel it. Therefore, shouldn't turning the knife often and removing material at the same angle cause a thin edge to form? I've found that I can get a knife extremely sharp without ever even checking for a burr at all! In fact, without even condsidering the burr.
I know a knife can be sharpened to a different bevel angle on each side, but during the sharpening process the different angles would have to be maintained each time the knife is turned.
Here is something else that might be happening. Image down at the edge, what happens if the knife were rocking from side to side whilst sharpening one side. If the rocking towards the edge always stopped in _exactly_ the same place, it would form a nice convex bevel. But it it went over center, even just a little, it would destroy the edge each time, almost as if you were trying to produce a butter knife. In this case the flipping and grinding would maintain a nice, dull edge, until the knife simply vanished.
Here's another way to think about it. Let's say you take one pass on one side and form an edge at some angle. If on the next pass, the blade is rocked so that it becomes more perperdicular to the wheel, a new edge would be formed at a sllightly different angle. Back and forth, back and forth, each pass forming a new edge at a slightly different angle. If the knife were rocked the other direction so that the edge was not contacting the wheel, then it would just be forming a secodary bevel.
I'm guesing here, but I suspect that if the knife is dissappearing and never getting sharp, that might be what is happening? Does that make sense to you too? Also, on tiny blades, it does not take much time or pressure!
BTW, that little jig add-on thing, got that little blade scary, razor sharp, very quickly. :)
Quote from: grepper on March 11, 2013, 11:56:31 AM
Does it not stand to reason that if you remove metal from one side at particular angle, and then do the same on the other side, that the knife will become sharp?
Yes, but that occurs when those two angled surfaces meet. I'm trying to find a method to tell when that happens. I guess that if you can't see or feel the bur you just have to keep a close eye on those two bevels. If bevel A is wider than bevel B, and then you flip and grind on bevel B until it's the same width as bevel A I guess that's when you know you're there.
QuoteHere's another way to think about it. Let's say you take one pass on one side and form an edge at some angle. If on the next pass, the blade is rocked so that it becomes more perpendicular to the wheel, a new edge would be formed at a sllightly different angle. Back and forth, back and forth, each pass forming a new edge at a slightly different angle. If the knife were rocked the other direction so that the edge was not contacting the wheel, then it would just be forming a secondary bevel.
I'm guessing here, but I suspect that if the knife is disappearing and never getting sharp, that might be what is happening? Does that make sense to you too? Also, on tiny blades, it does not take much time or pressure!
Yes, that makes perfect sense and may explain why freehanding doesn't work so well for me.
"Yes, but that occurs when those two angled surfaces meet. "
No doubt about that!
"I'm trying to find a method to tell when that happens. "
What if, for arguments sake, you couldn't tell? If you just blindly, gently sharpened each side equally, the two angled surfaces would eventually meet and suddenly the knife becomes sharp regardless of how well informed you are of what's going on right at the edge.
That's what I do a lot of the time. I check for sharpness often. Oddly, it suddenly becomes sharp. That's when I know to really take it very easily, with very little pressure, being careful to not muck up the edge. Almost just a polish before a quick, light hone.
I've probably never got the two bevel angles exactly, precisely the same, down the micron level, but I'm not sure that matters. It's still really close, and gets _very_ sharp.
BTW. What a beautiful Old Timer you have there. What fine, worn, earthy patina. I just want to hold it in my hand. (And sharpen it :) )
Quote from: grepper on March 11, 2013, 02:06:40 PM
BTW. What a beautiful Old Timer you have there. What fine, worn, earthy patina. I just want to hold it in my hand. (And sharpen it :) )
Notice how much of the blades have been worn away. I have this "eraser" that I rub over the blades to clean them up and give them a shine.
Neat idea, Mark. Was any deflection of the blade noticeable?
Hi There Elden,
Sorry, but I'm not sure what you are asking.
Did the tin hold the blade rigidly enough so that the blade edge didn't move up (change angles) when pressed against the grinding wheel?
I think he means did the knife blade angle stay constant.
Leave to the pros to say what I mean! ;D
No problem with the blade moving in any direction. It's held tightly against the jig and the handle helps with keeping it stable too.
You have to keep in mind that this is a very small knife, so very little pressure is exerted on the blade during sharpening, but it was surprisingly stable anyway.
Like I mentioned earlier, with larger knives with a larger tang, there could be maybe 3 different sizes of add-ons that would cover about any knife that you could not place directly in the jig. The larger the tang, the larger the add-on and the more tightly it could grip the tang. I suspect that with better materials and some engineering, a knife could be gripped very firmly.
I had freehanded the little knife on the Tormek prior to sharpening it with this advanced, highly scientific and technical extreme jig system, and had gotten it pretty sharp. Now, it's even sharper. :)
Quote from: grepper on March 11, 2013, 07:40:19 PM
I had freehanded the little knife on the Tormek prior to sharpening it with this advanced, highly scientific and technical extreme jig system, and had gotten it pretty sharp. Now, it's even sharper. :)
I'm having trouble judging the sharpness. What's your method?
Well, huh. There is the hanging on the fingernail at a very small angle.
Pressing, with little or no slicing downward on the edge of paper and carving gentle curves.
Various paper is much harder than other paper. Try hanging a piece of paper both in both directions. Take a piece of 8 1/2 x 11 paper and hang it vertically holding it from the 8 1/2 in side at the top and slice down through the long edge. Then try it the other way by holding the long side on top and slicing through the vertically hanging 8 1/2 in side. Amazing how different cutting with/against the grain of various paper is.
Try some of the thin, shiny inserts that come in newspapers. Some are very hard to cut against the grain.
Try paper towel for a real challenge. Grab on to the top and stretch a small portion between your fingers and try to slice downward. Some paper towels are very tough to not tear whist cutting.
Get a long single human hair. Hang it vertically from a pair of pliers. Chop it in half with a Kung-Fu slice.
Get a commercial razor blade and do the same so you have something to compare your artistry to. If you can say they are similar, I'd say it's razor sharp. Scary sharp!
The ultimate: get a medical scalpel. Be careful with it. They are _damn_ sharp. Much sharper than a razor blade. Do the same tests and compare your edge to a scalpel... Good luck!
Oddly, get a rotten tomato. Try to press down through the skin with little slicing... Good luck! :)
By having a known quantity for comparison you can say it's razor sharp! It's scalpel sharp. It's SCARY sharp!
Tests of sharpness:
Does the edge catch on your fingernail?
Will it shave calloused skin? (dangerous test if you're not fairly confident in your edge and your dexterity)
Does it cut standard #20 printer paper without leaving a ragged edge?
Can you change direction of the cut in the paper whilst cutting?
Can it cut across the end grain of a piece of open-grained soft wood without tearing? (balsa and fir are best test)
Will it easily shave the hair off your arm? (no spit, no pressing, just glide)
A not so macho alternative to the thumbnail would be a plastic pen. (Not orginal with me; I forget the source.)
Ken
Quote from: Jeff Farris on March 12, 2013, 04:47:06 PM
Tests of sharpness:
Does the edge catch on your fingernail?
Will it shave calloused skin? (dangerous test if you're not fairly confident in your edge and your dexterity)
Does it cut standard #20 printer paper without leaving a ragged edge?
Can you change direction of the cut in the paper whilst cutting?
Can it cut across the end grain of a piece of open-grained soft wood without tearing? (balsa and fir are best test)
Will it easily shave the hair off your arm? (no spit, no pressing, just glide)
If this isn't a classic for the sticky then I don't know what is....this succinct, punchy useful bullets is exactly whats needed. People have a clear set of tests they can perform and relate to instead of esoteric measures of sharpness like....."scary sharp". Of all the euphemisms for sharp, that has to be the most loathsome
Quote from: Ken S on March 12, 2013, 04:58:16 PM
A not so macho alternative to the thumbnail would be a plastic pen. (Not orginal with me; I forget the source.)
Ron Hock. I read that just last night. He also mentions running the edge along the end of your thumbnail, with great care of course, applying only the slightest force. Any flats, nicks, or imperfections in the edge will telegraph through and you'll feel them. I tried this and it works well.
Thanks, Herman. I hope you are enjoying Ron Hock's book. He also has an interesting blog on his website.
Ken
Oh no! Another thread on what is sharp!
I think the question, what is sharp, is interesting. Ask anyone to name something really sharp, and a razor blade is often the first response. Yup. A razor blade is rather sharp.
So if someone asks if their knife is sharp, without the benefit of a scanning electron microscope, this a great way to explain it:
Get a new razor blade and perform all of the standard home sharpness tests that have been described above. Then try the same tests with the blade you just sharpened. How does their cutting performance compare? That gives a very good idea of how sharp something is because the sharpness of a razor blade is well understood. Everybody agrees that a razor blade is pretty sharp.
If your knife can cut 20# printer paper against the grain smoothly, that's pretty sharp. Try facial tissue or paper towel. Get a "feel" for various paper products against the grain. There are many that are much more difficult to cut cleanly than printer paper, requiring a much sharper edge.
Sharp is such an ambiguous term, but in comparison to other blades it can at least be put into understandable perspective.
I think it all depends on what folks "think" is sharp. Obsidian scalpels used in ocular surgery, or plasma polished diamond blades can have edges hundreds of times thinner, (sharper), than a fat, "dull" razor blade. Now, I'll bet those things are, (rhymes with very), sharp! :)
http://www.finescience.com/Special-Pages/Products.aspx?ProductId=296&CategoryId=56
Quote from: Ken S on March 12, 2013, 09:13:36 PM
Thanks, Herman. I hope you are enjoying Ron Hock's book. He also has an interesting blog on his website.
Yes, Ken, thanks for recommending that book. I enjoyed the section on the metallurgy of steel. Reminded me of my grad school days and our experiments with silicon.
Quote from: grepper on March 12, 2013, 09:43:49 PM
Get a new razor blade and perform all of the standard home sharpness tests that have been described above. Then try the same tests with the blade you just sharpened. How does their cutting performance compare?
Hey grepper, do you notice any difference in the sharpness with the edge angle? I would think that the smaller the angle the sharper the edge.
Leonard Lee has a thing or two to say about that which makes really good sense.
Bottom line...for all kitchen knives that are destined to slice flesh and veg only.....10 to 20 degrees included angle.
For those destined to chop through bone or heavier duty stuff....much greater..30+ right up to cleavers which were discussed recently
Herman,
That is really a very good question! You are pain Herman! :) Making me think too hard. I love it!
Thinking out loud:
To answer your question, at what bevel angles could you start to notice the difference cutting something like paper? I'm not sure, but I doubt you would notice much difference between 10-20 degrees. What do you think?
Then there is the whole question concerning the difference between very first edge contact vs plunging into some material when side resistance would increase as the plunge depth increased.
Does a smaller bevel angle mean that at the microscopic level, exactly where the bevel angles meet, a smaller bevel means thinner? I'm going to have to think on that one. What if right where the bevel meets either at 10 or 20 degrees, the very edge was only one atom wide? One would get "duller" more quickly with a fatter bevel, but the very leading edge would be the same.
Hmmmm.....! I presume you ask because a razor could have a smaller angle bevel than a kitchen knife, and therefore it would be very difficult to ever get a kitchen knife as sharp as a razor? So, when trying to judge sharpness, the comparison is not fair?
Here's some light reading: http://www.ucd.ie/mecheng/staff_pages/pdfs/Gilchrist_2007a.pdf
Look at the bevel angles on a standard razor blade. A 16 degree bevel. Not that different than a 20 degree kitchen knife.
(http://tinyurl.com/b3tlqzr)
Yes, but the question is, do these different edge angles make a difference when we put them through the sharpness tests?
Herman!!!!
You reduced my long winded diatribe, complete with scientific documentation, to the exact same question that you asked in the first place. :) Doh! ROFL.
Ok. The answer is no. I don't notice a difference... Except for once..
I sharpen all knives to about 20 degrees. I've tried 10 and 15 degrees, but I did not notice that much difference for the effort. Now, I'm no sage o' sharpening or anything, but I've found that 20 degrees works well. I can get that angle very sharp, easily passing the home sharpness tests. Very useable and durable. You might be able to get 15 degrees sharper, but for practical purposes, I don't bother with it.
However, I did sharpen one knife to 12-15 degrees and was able to cut a single hanging hair. It was very sharp indeed, but dulled rather quickly.
I think the comparison to razor blade sharp if a good one for a knife that you are going to actually use. Anywhere around that sharp, is, well, sharp enough.
Well, I would not do _all_ knives to 20 degrees, but kitchen, pocket and general use knives seem to do well there, and I don't have to think about it.
So I think it boils down to either sharpening for very impressive everyday use, or sharpening to see just how freek'n sharp it's possible to make a knife. (Which is very cool). But if the latter, then the Tromek is not the end all. You need to study sword and straight razor sharpening, very fine wet stones, sandpaper, and hours of loving blade care.
Quote from: grepper on March 13, 2013, 03:01:28 AM
Herman!!!!
You reduced my long winded diatribe, complete with scientific documentation, to the exact same question that you asked in the first place. :) Doh! ROFL.
No. I didn't! I was responding to Rob while apparently you were doing the same!
Quote from: grepper on March 13, 2013, 12:30:48 AM
To answer your question, at what bevel angles could you start to notice the difference cutting something like paper? I'm not sure, but I doubt you would notice much difference between 10-20 degrees. What do you think?
I've noticed a difference between an edge angle of 30
o and 40
o. I think. It's hard to say because there are so many other factors that affect the paper test. The quality of the steel, the polish on the bevel, etc. All due to the skill of the sharpener!
QuoteDoes a smaller bevel angle mean that at the microscopic level, exactly where the bevel angles meet, a smaller bevel means thinner? I'm going to have to think on that one. What if right where the bevel meets either at 10 or 20 degrees, the very edge was only one atom wide? One would get "duller" more quickly with a fatter bevel, but the very leading edge would be the same.
Very very
very far from it. Look, for example, at the photograph you posted. There's a legend identifying a length of 200 μm. Now look at the width of the edge of the blade in that photograph. I estimate it at no less than 10 μm, and it's probably larger than that.
According to a Google search I just did iron atoms have a diameter of about 0.074 nm, or 0.000 074 μm.
So, let's do a little calculating here. The width of the edge on that blade in your photograph is probably larger than 10 μm, but even if it were that small that would give us (10 μm)/(0.000 074 μm), or about 135 000 atoms!
We need to look at the larger structures, which are the ferrite crystals. Not sure how big they are as I'm sure it depends on how the steel was created and subsequently heat treated. My guess is that they contain thousands of atoms, and that the edge is thousands of crystals across.
If this stuff interests you take a look at what a very famous physicist and delightful character, Richard Feynman had to say way back in 1959. http://en.wikipedia.org/wiki/There's_Plenty_of_Room_at_the_Bottom
Quote from: grepper on March 13, 2013, 03:01:28 AM
Well, I would not do _all_ knives to 20 degrees, but kitchen, pocket and general use knives seem to do well there, and I don't have to think about it.
I agree, Mark. A 20
o bevel angle, equivalent to a 40
o edge angle, is about right for most of my knives, too. It's a good compromise between sharpness and durability.
The thing is, I bought this kitchen knife because a reviewer claimed it was thin and had an edge angle closer to 30
o making it better for slicing veggies. It passes the paper test of sharpness better than any knife I've ever sharpened. I guess that when it gets dull and I have to sharpen it I'll find out how good I am. The thing is, the knife is so thin I can't measure the edge angle with the angle master and a magnifying glass!
Herman,
Do you like the knife? What knife?
Interesting, this what is sharp stuff.
I guess the real sultan of sharp is currently plasma polished diamond blades. Reportedly, edge curvature of 2 nm! Wow. That makes a 1 micron razor blade edge look like a baseball bat. 1 micron is 1000 nm, so they are making blades almost 1000 times sharper than a razor blade. Rob- Could I call that scary sharp? :)
Hmmm.... I wonder how that would do on our home sharpness tests? I think I might go for the hang on a plastic pen rather than my thumbnail as I'm not sure that it would even notice a thumbnail was there. They don't even seem to mind a rather blunt bevel, "45° and 20° trimming tools for both room and cryo temperatures." And, "It can be sterilized in an autoclave up to 200°C". Pretty fancy stuff.
http://www.emsdiasum.com/microscopy/products/diamond/intro.aspx
And hey kids! We can buy them:
http://www.emsdiasum.com/microscopy/products/tweezers/diamond_scapel.aspx
Would someone here please pick up on a handful of these and then let us know what you think.... Is it sharp?
Quote from: grepper on March 13, 2013, 02:00:29 PM
Do you like the knife? What knife?
Victorinox 40520 Fibrox 8-Inch Chef's Knife
http://www.amazon.com/gp/product/B008M5U1C2/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1
I like the knife very much and have posted about it before, I think. Saw it on the PBS show Cook's Country. They have a feature called the Test Kitchen where they review products. This one was about what they call hybrid knives, knives that borrow features from both western and eastern cultures. It's like a western kitchen knife but the curve is more sweeping, and like eastern knives it's thinner and has a sharper bevel angle.