Testing for Sharpness

[Anonymous]

It creeps the hell out of me that someone has chosen a similar path in life. I’ll  be 71 in a month..I’m married 50 years, and every label in my house: cabinets, shelves refrigerator, pantry all are facing forward an readable at a glance.

The folding money in my pocket has to be oriented in a manner that had every bill facing up and in the same orientation both horizontally and vertically.

That’s who I am. Lol

[cbwx34]

CliffCurry wrote:

Please share your own methods that you use for testing….

The Edge Tester I mentioned in the other thread is a quick and easy way to test for sharpness and some of the issues with an edge like small chips or burrs. (Nice thing is, you don’t have to unclamp a knife to use it).

I don’t really test for “ultimate sharpness” very often, which may be what you’re looking for, but when I finish a knife, I test it for sharpness and durability. It should be able to slice newsprint or phonebook paper easily, that pretty much tells it’s properly apexed and burr free. But I now also make a couple of cuts thru something like a cardboard box or these cardboard cards I get in the mail, then recheck with PB paper or newsprint. I’ve found that if an edge has any issues, it will show pretty much right away, if it passes this, it should hold for a while.

2 users thanked author for this post.

Frans, CliffCurry

[Anonymous]

This is how I feel about all this paper cutting stuff… If paper cutting was the  prime function of a particular knife. I would use paper to test it, after all cutting paper is a prime function for any knife ( joke )

I can get any blade to cut paper, even using # 600 grit as my final media…  Not sure how slicing through paper will equate to cutting cucumbers or carrots on a cutting board..  of course they will cut the cucumber if they cut paper, but how many carrots can an edge so sharp actually cut before having to re  sharpen ?.. so for me.. the purpose of a knife’s function, is the determing factor to how I sharpen it… not if it cuts through PB paper..

in my opinion.. cutting paper is a parlor trick. it looks good but serves no real function. That is unless you have desire to slice a lot of phone book paper.

You can easily cut through paper with a straight razor, but would you want to use a razor to cut 25 carrots? 25 stems of celery on a cutting board. , Not being argumentative just offering some reality to the function factor of a knife. WE all want a sharp knife, but we also want one with edge retention, the balance of sharpness to edge retention is a value that is very subjective. Ill take a slightly sharper knife and touch it up more often because I have the time to do so.. Sharpness is the mecca of a knife, but what good is a sharp knife if you have to sharpen it every time you use it.. A razor cuts whiskers on a smooth skin surface.. and yet that sharpness is necessary… but also a razor usually requires a touch up after each use. I’m rambling.. sorry its late and the drugs are kicking my ass.

[CliffCurry]

Im sorry your not feeling good Bill.

1 user thanked author for this post.

[cbwx34]

Anonymous wrote:

This is how I feel about all this paper cutting stuff… If paper cutting was the prime function of a particular knife. I would use paper to test it, after all cutting paper is a prime function for any knife ( joke ) I can get any blade to cut paper, even using # 600 grit as my final media… Not sure how slicing through paper will equate to cutting cucumbers or carrots on a cutting board.. of course they will cut the cucumber if they cut paper, but how many carrots can an edge so sharp actually cut before having to re sharpen ?.. so for me.. the purpose of a knife’s function, is the determing factor to how I sharpen it… not if it cuts through PB paper.. in my opinion.. cutting paper is a parlor trick. it looks good but serves no real function. That is unless you have desire to slice a lot of phone book paper. You can easily cut through paper with a straight razor, but would you want to use a razor to cut 25 carrots? 25 stems of celery on a cutting board. , Not being argumentative just offering some reality to the function factor of a knife. WE all want a sharp knife, but we also want one with edge retention, the balance of sharpness to edge retention is a value that is very subjective. Ill take a slightly sharper knife and touch it up more often because I have the time to do so.. Sharpness is the mecca of a knife, but what good is a sharp knife if you have to sharpen it every time you use it.. A razor cuts whiskers on a smooth skin surface.. and yet that sharpness is necessary… but also a razor usually requires a touch up after each use. I’m rambling.. sorry its late and the drugs are kicking my ass.

That’s a fair assessment, one I’ve had myself at one time.  So, maybe this will help.  One thing I think you’re misinterpreting is that a really sharp knife somehow equates to a weak edge that won’t hold up as long, or has lower edge retention.  That’s because the comparison is made to what you did… a straight razor, which by design is a thin edge that wouldn’t hold up to carrot cutting, etc., and also has to be maintained at a high level to perform it’s intended use. There’s a bit more to this part, but that’s the basics.

The reason I and others use things like phonebook paper, or thin newsprint, is because you’ll find, as your ability to get a knife “sharper than new” (or whatever your baseline is), that cutting regular paper, or some of the more traditional tests, don’t tell you as much.  A knife you thought was sharp because it cut thru notebook paper, may no longer seem like a big deal.  So you look around for something that tells a bit more.  Thinner paper will give a better idea of the level of sharpness, that it’s properly apexed, if there’s any burrs, etc. Plus it’s easy to get. 🙂

The reason I also test it on something harder to cut is because you’re also right that cutting thin paper or some of the other tests can be a bit of a “parlor trick” if sharpened specifically for that task… I could get an edge that would do that, but then when I go to cut something else, the edge immediately fails, because it has a wire edge, or too thin, etc.  So a 2nd test for durability, then another quick slice thru thin paper to make sure nothing showed up.

So,  basically, if done right, it’s not a knife sharpened for the task of cutting PB paper, it’s just a test to insure the sharpening is being done correctly, and to the desired level.

4 users thanked author for this post.

Gib Curry, Frans, CliffCurry, wickededge

[Montana Edge]

Yep. Well put.  I would add that the sound of slicing paper tells me loads too.

 

1 user thanked author for this post.

CliffCurry

[Gib Curry]

 

Most people I’ve sharpened for, I’ve used the standard paper test when they give me the blade…. have them do it so they can see, feel & hear what it sounds like.  Might even have them slice a tomato or cucumber (job dependent to the knife).

Then, when we do the after, they, too, can see, feel and hear the improvement.  Slice the old cucumber again and see “that” look in their eye…. knowing that they are having that “OMG this is sharp” moment of sublime satisfaction.

cbwx34 wrote:

……..I’ve found that if an edge has any issues, it will show pretty much right away, if it passes this, it should hold for a while.

This point highlights where I lack confidence and I question my edges…. the part I can’t control.  How long will it stay sharp?

Again emphasizing the importance of matching knife profile, materials, edge geometry, function AND person to the sharpening being done.

(He says as he listens to the clickity-clak of paring knife cleaning an apple on a glass cutting board wafts from the kitchen.)

Clay, now that I’m getting better at visualizing a sharp edge, I shudder to think of what those glass cutting board edges look like under your scope.   …. a near mirror polished 180 degree (inclusive) micro-bevel!!

 

~~~~
For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

1 user thanked author for this post.

wickededge

[Josh]

Cutting paper *Can* be a “parlor trick”… depends on how you do it 😉

Paper has a sort of grain in it that runs the length wise of the paper (from top to bottom). Most people cut at a 45° angle diagonally across the paper and call it good. If you want to check sharpness more then you need to cut 90° across the paper with and against the grain, on both a 45 and 90° angle. The hardest cut is to do a 90°/90° across the grain a half inch or more from the point of hold.

Paper cutting, in my opinion, has more to do w/ geometry (edge angle and thinness of the shoulders behind the edge) than sharpness unless you are doing it correctly…

Curtis that’s a great idea cutting into the cardboard!

[Anonymous]

I think everyone is dismissing my input as that from a novice..( I am in fact a novice  )  But my point was that cutting paper shows how sharp a knife is at cutting paper. That doesn’t mean it wont cut other stuff.  Josh pointed out refining the paper cut to cross cut the grain of the paper… I’ve been at this two months and know nothing, yet I can slice a piece of paper in a continuous “S’ pattern down the whole length of a piece of paper.. cutting both with the grain and against the grain in an S pattern and then cut another one an inch away from that one. My point was that cutting paper held in the hand does not tell how many hard carrots or pieces of celery or chard can be cut when that edge hits the chopping block after each slice. It doesn’t show how many cuts can be made in a 1/2 inch piece of hemp twine.   As I said before, I could do magic with a razor on a piece of paper, but would I cut pork chops with a razor? That was my point.  Cutting paper proves you can cut paper.

[Frans]

If you need a knife for cutting carrots, than I would adapt the edge for that and than test how many pieces I can cut with it. If I would sharpen a razor, I would try the hanging hair test and how it shaves. I use paper cuts as it is a very easy, cheap and useful test for overall sharpness regardless the cutting purpose and to see/hear/feel if the edge catches. It has nothing to do with magic or a parlor trick.

As a French knife maker once said:

I do not shave with a kitchen knife and I do not prepare food with a razor.

[Mark76]

Frans wrote:

I do not shave with a kitchen knife

Here’s my friend Michiel:

Molecule Polishing: my blog about sharpening with the Wicked Edge

[cbwx34]

Anonymous wrote:

I think everyone is dismissing my input as that from a novice..( I am in fact a novice ) But my point was that cutting paper shows how sharp a knife is at cutting paper. That doesn’t mean it wont cut other stuff. Josh pointed out refining the paper cut to cross cut the grain of the paper… I’ve been at this two months and know nothing, yet I can slice a piece of paper in a continuous “S’ pattern down the whole length of a piece of paper.. cutting both with the grain and against the grain in an S pattern and then cut another one an inch away from that one. My point was that cutting paper held in the hand does not tell how many hard carrots or pieces of celery or chard can be cut when that edge hits the chopping block after each slice. It doesn’t show how many cuts can be made in a 1/2 inch piece of hemp twine. As I said before, I could do magic with a razor on a piece of paper, but would I cut pork chops with a razor? That was my point. Cutting paper proves you can cut paper.

Well this is a thread on “Testing for Sharpness”.  You seem to be focused on durability.  But I am curious about what testing you’ve done on what you mentioned (carrots, rope, etc.) and the results?

[Anonymous]

Frans wrote:

If you need a knife for cutting carrots, than I would adapt the edge for that and than test how many pieces I can cut with it. If I would sharpen a razor, I would try the hanging hair test and how it shaves. I use paper cuts as it is a very easy, cheap and useful test for overall sharpness regardless the cutting purpose and to see/hear/feel if the edge catches. It has nothing to do with magic or a parlor trick. As a French knife maker once said: I do not shave with a kitchen knife and I do not prepare food with a razor.

THAT WAS MY POINT>>>>>>>> I have NO Need to cut paper, so why use paper as a test…  I understand you can tell the difference between dull and sharp with paper, but just how sharp does it have to be for shaving, certainly not as sharp for cutting carrots  sharp is one thing, edge retention is another. you cant tell edge retention with paper.. and edge retention is just as important as sharpness. But as I say on every forum I’m in, there is always a trade off. More sharp, less retention.. give a sous chef a razor to cut the restaurants daily requirements of  product, and he will be fired, or shoot himself. But “he tested his chef’s knife with a piece of paper, and it was amazing..

If I’m going to sharpen a knife, I will sharpen it for the purpose intended. I have been saying that all along. I can cut paper with a 18* degree edge, and I can cut paper with a 10* edge.  but there are times when 18* is necessary and times when 10* are necessary, one wont  work in the others shoes. Yet both will cut paper… if they wont cut paper , they are dull.

[Victor]

Paper cutting tricks?

 

No point I am trying to make, but….

 

 

 

 

But I have not seen anyone can duplicate the original sharpness other than spend $60 and send it back to Japan for resharpen! Hehe

 

1 user thanked author for this post.

CliffCurry

[Anonymous]

I think I am going to take a break from all this stuff and the forum.. allow you guys your pleasure. Its been nice for the most part… I’ve learned a good bit in a short time…sharing my thoughts here, not so much .

Bill

 

[Author]

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