thanks for the advice cliff

[MikeMade™]

I just sharpened up my Rukus using the microbevel honing technique.... WOW! I started with a 20 degree main bevel and I'm pushcutting newsprint, and tree topping armhairs. I took er' all the way up to a 1200 grit spyderco ceramic, then went a step further with 2 strops. One loaded with boron carbide, the other with chromium oxide. What other sharpness tests can i try out just to see how good the edge is on this thing?

 

[Cliff Stamp]

If you really want a challenge then you can try :

1) pinch a hair between your thumb and index finger and try to push the knife through it

2) try to push cut single ply toilet paper

A fairly decent and easy way to measure sharpness is to just take a piece of newsprint and hold it between your fingers and see how far away from your fingers you can just push the blade straight into it. The distance of course depends on the qualities of the paper but if you use the same type consistently you can thus guage your progress fairly accurately.

-Cliff

 

[matt321]

Cliff,
What's the conversion factors for equating push cutting computer printer paper versus newsprint versus single ply tp?

 

[gunmike1]

Cliff,
What's the conversion factors for equating push cutting computer printer paper versus newsprint versus single ply tp?

The real world conversion is it is extremely easy for a knife to push cut copy paper, even with a pretty crappy edge on it. After a little practice you can get it to pushcut newsprint, as your skill improves you can pushcut newsprint farther away from the point where you hold it (over an inch is good, the best I've seen is 4" away on a Ben Dale sharpened knife). When you can push cut toilet paper, you are a sharpening God (at least in my book).

 

[sodak]

The best I've been able to do is about 2.5 inches on newsprint. I've *never* come even close to single ply toilet paper, but I've seen pictures of those who have, and it is impressive. Have fun!

By the way, when I strop my straight razors and they aggressively tree-top trim arm or leg hair along the entire edge, they are ready for my face. If you can do that with your knife, you're doing good!

 

[Cliff Stamp]

What's the conversion factors for equating push cutting computer printer paper versus newsprint versus single ply tp?

The easiest way to determine this would be to see how far out on the various papers you can push cut away from the point of tension. This inverse distance would then tell you how effective they are at guaging sharpness. In the extreme for example, if you used a piece of thin balsa you would find that it is near useless because the wood is so stiff than a very blunt blade will still push into it.

Basically what you are using to measure the sharpness is the strength of the paper. As you move out away from the point where the paper is held it will eventually bend before it is cut. Push cutting normal stock paper puts your blades sharper on average than all knives I have seen by a wide margin. Being able to push cut newsprint significantly away from the point of tension (1"+) is at the level of the best knives I have seen including the handle sharpened ones by those commonly regarded as experts like Ben Dale. I don't know if it is possible to sharpen a knife to push cut single ply toilet paper because it is so flimsy so it is an example of trying to break the sound barrier.

-Cliff

 

[Dog of War]

.... as your skill improves you can pushcut newsprint farther away from the point where you hold it (over an inch is good, the best I've seen is 4" away on a Ben Dale sharpened knife). When you can push cut toilet paper, you are a sharpening God (at least in my book).

4" is impressive. Did Ben explain how he achieved this, "regular" EdgePro technique or did he do some extra finessing?

Also wondering, how large a piece of newsprint do you use when testing, and do you hold it with the edge of the paper you're cutting horizontal, or do you let it hang at at angle? I've come to realize that at these levels of sharpness the size of the test newsprint and the weight added when using larger pieces is a factor.

 

[gunmike1]

Ben Dale said he brought it up to the 3000 grit polish tapes at the 17 degree setting. That doesn't account for the angle of the blade, and my simple trig shows the edge closer to 11-12 degrees per side.

I push cut straight down into the newspaper (I use the same paper for consistency), held out horizontally. I usually take a newspaper, cut it so you have 1 page (front and back), and then cut it again at the center fold. I then usually cut that in 1/2, which gives you about 6" by 10" piece. For reference, I just retested the R2. With a whole page front and back, without cutting the paper at the fold in the middle it iniated a push cut 6.23" away from the point of hold, which was the about an inch in from the upper left corner. It then had trouble continuing through with the cut. There is a lot of floppy weight that you can slightly move with your hand to increase the tension (which I did a little to cheat), which is probably why it could initiate the cut so far out, but not continue it. With my normal 6" by 10" piece it managed 3.51" from point of hold (it's been lightly used since I first tested it, and my Jess Horn just did 2.37" on this size), and continued straight through with the cut. I just pinch it between my fingers and push cut straight down into the paper with my standard test like this, and hold it maybe an inch in from the upper left corner. If the paper bends and the knife doesn't cut in well before the newsprint rips at the point I am holding it the knife has failed to make the cut. I hold my hand as steady as possible and make every effort to be consistent and not "help" the knife start the cut. On a 3" by 3" square it made a pushcut 2.51" away from the point of hold. So there is quite a variance. When you factor in the difference in technique and the thickness of the newprint we are all probably talking apples and oranges in oue comparisons. For all I know my 4" cut is someone else's 3" cut. That is why I like Cliff's thread tests, they don't lie and are much easier to control and be consistent. A spring scale for tests like that is on my shopping list.

I always go by additional factors like shaving to judge the sharpness of my knives, but since I keep my newprint tests as consistent as possible I find that they are helpful in giving me feedback on my sharpening skills and consistency.

 

[MikeMade™]

when you guys reference push cutting newspaper, would that mean holding the top edge of the paper parallel to the ground and push cutting straight down, or holding the top right corner between your fingers and pushcutting straight down through the diagonal right edge of the paper?

 

[gunmike1]

when you guys reference push cutting newspaper, would that mean holding the top edge of the paper parallel to the ground and push cutting straight down, or holding the top right corner between your fingers and pushcutting straight down through the diagonal right edge of the paper?

I'm talking about pushcutting with the top of the newspaper parallel to the ground, and cutting straight down into it at 90 degrees.

Edit to clarify: I hold the newspaper straight out in front of me, holding the top edge with the paper hanging freely, in a perpendicular plane to the ground. I then cut into it straight down, cutting from the top of the paper to the bottom. It was late last night when I responded and I was basically trying to say that the top of the paper is in a straight line, not at an angle. And as Cliff says, going with or against the grain makes a huge difference.

 

[Cliff Stamp]

Cutting into, or on a diagonal, is much easier. Paper also has a grain so it is much easier to cut into one side than the side which is 90 degrees rotated.

-Cliff