As sharpening skills increase and the amount of available arm hair has diminished I have sought out new tests that allow the amazing edge keenness achievable with the WEPS to be shown.
Yeah you can tell a lot just from arm hair by how it “pops”
All depends how far down the rabbit hole you go…forgot to link Frans van de Kamp’s awesome vertical slice of a cigarette paper! https://www.youtube.com/watch?v=0c-la7uG5Xo
Glad your having fun Bill, I was thinking of you(and others) when I posted this so you could have a few new ideas how to test for increasing levels of sharpness as your knives continue to progress. Hopefully people will share more if they know of them…
To my own shock my kitchen knife wouldnt pass the free standing folded paper test so guess what I was working on today. That ones a bit tougher then it looks, or maybe my paper is damp…yeah thats it, damp paper!
Bill, I learned much by watching videos done by Cliff Stamp. He has high level knowledge and applies it at a ground floor level with rigorous testing. You may enjoy those…
The general idea(someone correct me if Im getting this wrong) is to narrow the bevel angle…for whatever knife, steel, or specific used…until it fails either by buckling or chipping during use.
The solution: Increase the angle by a degree or 2 and test again…until it doesn’t and viola you have found the optimum angle for that knife/steel/use. Cool beans?
As far as a practical, easy to do test for sharpness, to determine a level of refinement in the apex of a secondary bevel? I still like the whittling hair test…just dont pull it out of your wifes head(she seems to not like that so much!)
Kitchen knife I was doing some testing on tonight. Im happy with the results of new technique!
The best test I’ve found is inspection with the USB ‘scope. I look directly down on the edge and focus on the apex, then slowly move from heel to tip. A truly sharp edge will reflect no light. Even the smallest burr will show up as a glint along the edge. If the edge looks good at 50X and I really want the sharpest edge possible, I will go to 180X and reinspect the full length again. Of course, each blade get the paper slicing test before sending it home.
I will also inspect for a centered apex by holding the ‘scope dead vertical and watching for differences in the width of the bevels. If it looks wrong, I’ll roll the ‘scope from side to side to get a better view.
BTW, I often use the ‘scope as a measuring tool by capturing an image and measuring features with the software. For instance, my wife has a very expensive wrist watch and one of the very small pins attaching the band to the watch fell out and disappeared. With the ‘scope I measured the hole diameter and found it to be 1.511 mm. Figured that the 11 microns was probably measuring error and ordered some 1.5mm rods on Amazon, saving about $90 in repair costs.
Bill has degrees in two disciplines: mechanical engineering and photography. I have a PE in two disciplines; mechanical and electrical engineering (sorry, no degree).
Bill is OCD, and I am ADD (which is why I've no degree).
We both have way more money in photographic equipment than we make use of.
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.
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.
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.
[quote quote=31617]…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. [/quote]
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!!
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!
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.
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?
I have sought out new tests that allow the amazing edge keenness achievable with the WEPS to be shown.
. It’s much thicker than mine.
… a near mirror polished 180 degree (inclusive) micro-bevel!!
