Ways to test sharpness?

[JGON]

It's just another level of sharpness past Hair Whittling.

The biggest things are it has to be extremely sharp and with no bur left on the edge at all.

When the edge is really good it won't have any TP on it after cutting through it. That means it's equally sharp down the whole edge, duller spots will have TP on them after the cut. Just another way to tell how good the edge really is.

Ankerson, does it matter what ply of TP is used? Is one type of TP more difficult than the other?
Also, I am beginning to get to the point in my knife sharpening where I might be getting close to accomplishing this level of sharpness, but I don't quite know if it's my technique or the tools I'm using that need work. I'm hoping you can give me some pointers...

Right now I use a coarse and a fine Japanese water stone, 1000 and 8000 grit to be exact. Coarse stone first, then the fine stone, and I use very light trailing strokes to finish the edge on that stone. When I'm done, the edge is mirror polished and will pop hair right off your arm. This I can do consistently. I then finish that edge on a leather strop with green sharpening compound, using the same strokes as when I finish on the fin stone, guiding the blade so the edge is moving back on the sharpening medium, instead of into it.

There are two levels of sharpness that I am NOT consistently able to achieve yet. Hair whittling, which I have achieved but cannot achieve consistently, and then TP slicing.

Are the tools I'm using going to get me there? Or do I need to get some sort of DMT or Diamond paste instead of or in addition to my green sharpening compound? Can any of you achieve a hair whittling edge consistently using two grits of stone and a leather strop, or am I missing some key element?

If I am not missing a key piece of equipment or key step, I guess I will have to admit the fact that my technique needs to be refined. One way or another, I will get there.

 

[Incahiker]

M390, ZDP-189, CPM-154 and the list goes on.

Those steels do take a mighty fine edge... especially CPM-154.. but what about S30V and D2. I mean, I can get them extremely sharp, but I have not been able to slice toilet paper with them.

 

[JGON]

All of my kitchen knives are dull also. I just don't have any quality knives that would hold an edge so I don't even bother sharpening them.

I bet you'd be surprised how sharp you could get those kitchen knives...

 

[CrimsonTideShooter]

I bet you'd be surprised how sharp you could get those kitchen knives...

I'm going to give my chefs knife a go on the sharpmaker while I'm having my coffee tomorrow morning. I'll report back. :thumbup:

 

[knarfeng]

Do you guys have any tests that you've come across that you use to see how sharp your knife is? I use the shaving/paper slicing method - but a knife doesn't have to be all that sharp to do that and I think mine are sharper than that. So what can I do to really test it out?

Depends on what you are trying to test.
If "ultimate sharpness", push-cutting news print and measuring how far from the point of hold works very well. The farther from your hand you can cut, the sharper the blade. "Push cutting" is just that, no slicing motion, just pushing against the paper.

If you just are looking for "working sharpness", try the finger nail test. Rest the blade at a 30° angle on your finger nail. If it will not slide, it is good to go.

 

[Ankerson]

Ankerson, does it matter what ply of TP is used? Is one type of TP more difficult than the other?
Also, I am beginning to get to the point in my knife sharpening where I might be getting close to accomplishing this level of sharpness, but I don't quite know if it's my technique or the tools I'm using that need work. I'm hoping you can give me some pointers...

Right now I use a coarse and a fine Japanese water stone, 1000 and 8000 grit to be exact. Coarse stone first, then the fine stone, and I use very light trailing strokes to finish the edge on that stone. When I'm done, the edge is mirror polished and will pop hair right off your arm. This I can do consistently. I then finish that edge on a leather strop with green sharpening compound, using the same strokes as when I finish on the fin stone, guiding the blade so the edge is moving back on the sharpening medium, instead of into it.

There are two levels of sharpness that I am NOT consistently able to achieve yet. Hair whittling, which I have achieved but cannot achieve consistently, and then TP slicing.

Are the tools I'm using going to get me there? Or do I need to get some sort of DMT or Diamond paste instead of or in addition to my green sharpening compound? Can any of you achieve a hair whittling edge consistently using two grits of stone and a leather strop, or am I missing some key element?

If I am not missing a key piece of equipment or key step, I guess I will have to admit the fact that my technique needs to be refined. One way or another, I will get there.

You would need to strop the edge to remove the bur completely and fine tune the edge.

2 Ply is tougher to cut, that's what I use.

Those steels do take a mighty fine edge... especially CPM-154.. but what about S30V and D2. I mean, I can get them extremely sharp, but I have not been able to slice toilet paper with them.

Yes I can do it with D2 and S30V, I don't think of them as super steels though.

 

[KennyB]

One thing I don't like is a knife that does a poor job, like you say if it easily and safely accomplishes tasks required of it then it is good. :thumbup:

Last Christmas I took my DMT Aligner with me to my mothers place - her knives are blunt junk! I just finished sharpening one when she got another out of the drawer to cut some potatoes, I said "I'll swap you" and gave her the one that I'd just sharpened while taking the other one to get that sharp. My favourite comment was when she first slice a potato with the knife I'd sharpened, she said "Oooooh" - that gave me a big smile!

There must be a lot of people like my mother - they buy a knife and use it, when it's new it cuts well then after a while it doesn't. It doesn't occur to them to sharpen it. Then you get us obsessive people that can shave hair and slice newspaper and then wonder if we can get the knife sharper. It's quite a contrast. When I walk into my mothers house the sharpest knives there would be on my SAK & LM Wave, when I leave the average knife sharpness in the house drops considerably!

Heh, I moved into a house with my friend and his family, and I volunteered to cut potatoes. I started out with their knives, and all of them were far too dull to cut the potatoe well at all. So I went and grabbed one of my knives, got the job done in about 2 minutes and his mother goes, "Wow you're done already?!"

Anyway, toilet paper goes far above shaving/hair whittling sharpness in my opinion. I have reached hair whittling with some fairly sloppily free-handed edges with a 1K stone and some green compound, and in fact my Leatherman ST200 just came with a hair whittling edge from the factory.

Toilet paper is untouchable though. I can hank a hair out of my chin and split it in half, but I can't cut toilet paper without it tearing for anything. As far as I'm concerned it's about the ultimate test of sharpness, passed letting a hair split itself with the force of gravity--and I've only seen Elmer Fudd pull that off.

I usually like to get my knives to the point where they will split hairs with a little bit of effort. Getting them hair whittling just takes too much time and wears out too fast for me. If I just need to sharpen a knife to "working sharpness" I like it to be able to fillet and push-cut phone-book paper--but it doesn't really need to push-cut it well, just doing it at all is enough for working sharpness for me.

I don't thin push-cutting newsprint and phonbook paper are that great of feats--no offense to anyone. I say this because I can push-cut through a whole page of newspaper, but that edge won't whittle hair or cut TP.

Edit:

Oh, and another way I like to test working-sharpness is with the Razor Edge Systems "Edge Tester". It's basically a plastic cylinder with two tapered points on the ends that make a nice tool for examining the edge. You don't really need a very sharp edge to get a "100" on their scale of sharpness, but it's really helpful for pointing out nicks, dings, burrs and of course for having a very easily repeated way of testing sharpness on the entirety of the blade, and it's only about $10. It doesn't really sound like it's worth it, but I've found it fairly useful for filed-sharpening; you don't always have a piece of paper around when you're sharpening.

 

[kreole]

Those steels do take a mighty fine edge... especially CPM-154.. but what about S30V and D2. I mean, I can get them extremely sharp, but I have not been able to slice toilet paper with them.

Just now I tried with a D2 small Bone Collector and S30V small Sebenza, and both were able to do it.

 

[JGON]

You would need to strop the edge to remove the bur completely and fine tune the edge.

I do strop, but maybe not enough. Leather strop with green compound. I know all compounds are not created equal, but I got mine through Bark River and I'm betting it's good enough.

How long do you strop for, or does it vary? Is there a certain amount of strokes that you do?

Thanks again,

JGON

 

[Ankerson]

You would need to strop the edge to remove the bur completely and fine tune the edge.

I do strop, but maybe not enough. Leather strop with green compound. I know all compounds are not created equal, but I got mine through Bark River and I'm betting it's good enough.

How long do you strop for, or does it vary? Is there a certain amount of strokes that you do?

Thanks again,

JGON

I don't strop.

I use the Edge Pro Apex and take it up to 6000 Grit Polishing tape, that's about 20,000 to 25,000 Japanese Waterstone.

 

[JGON]

I don't strop.

I use the Edge Pro Apex and take it up to 6000 Grit Polishing tape, that's about 20,000 to 25,000 Japanese Waterstone.

Are you sure it's not magic? I mean, have you ever tried to move a pencil with your mind or anything?

 

[CrimsonTideShooter]

Are you sure it's not magic? I mean, have you ever tried to move a pencil with your mind or anything?

Haha I'm with you. It's magic.

 

[JGON]

Haha I'm with you. It's magic.

Yeah. Definitely gotta be magic.

 

[jfindon]

I really wish I didn't suck so bad at sharpening, I can't get anything past shaving sharp. Even with the KME sharpener, I need someone to show me exactly what to do in person I guess.

 

[Jason B.]

Type of TP is very important here and personally I think this kind of sharpness will only be seen on something that holds perfect angles.

I question TP as a test because that type of cut can be made with a edge from a 600 or 1200 mesh diamond hone. Also any time I've ever tried the TP test after polishing a edge it would only glide on the TP and I'm talking about polished edges that will pass a HHT.

So its either a factor of the TP or the fact a guided device like the EP will produce a sharper point than any hand sharpening can compare too because of its perfectly set bevel angles.

What is your included bevel angles on the knives capable of the TP cut?

 

[Hawkings]

I really wish I didn't suck so bad at sharpening, I can't get anything past shaving sharp. Even with the KME sharpener, I need someone to show me exactly what to do in person I guess.

Shaving sharp is pretty good.
The sharpening discussed here is not the standard to judge a sharp knife by.
Shaving sharp IS a good result and does in no way suck.

Some times people (younger people more often then not, I'd wager) have a hard time understanding the difference between "pretty darn good" and "The best". The result being that "pretty darn good" is perceived to be sub standard, or suck.

 

[KennyB]

Shaving sharp is pretty good.
The sharpening discussed here is not the standard to judge a sharp knife by.
Shaving sharp IS a good result and does in no way suck.

Some times people (younger people more often then not, I'd wager) have a hard time understanding the difference between "pretty darn good" and "The best". The result being that "pretty darn good" is perceived to be sub standard, or suck.

Yeah, I obsess over getting things perfect a lot, but I think it's mostly because I set aside a lot of leisurely time to sharpen things in a kind of academic style where I can try different things. When it comes down to it, it takes me a lot of discipline for some reason to not take a dull kitchen knife and break out my benchstone just because it can't cut potatoes; I've kind of got to force myself to just put it on a steel until it's "good enough" to cut the spuds.

I think it just comes from not a lot of years of having to go with "good enough" to get a job done, but the more I do it the easier it gets. Plus I've found that when cooking, I can set my benchstone in the water to soak, go eat, and then have a bunch of energy to re profile the knife afterward.

Otherwise though I still obsess over my EDCs. When I watch TV, I'll tend to actually just listen to the TV for a few hours as I strop every EDC I carry; regardless of if I even used it that day.

Anyway, that's a little offtopic, but I do wind up going through a phonebook ever month or two. That's why I don't think $10 on an EdgeTester is a bad investment, at least for checking edge imperfections--the actual plastic is pretty easy to cut into so it isn't really a good gauge of overall sharpness in my opinion. Passing it through phone book or newsprint can't detect things like dings, nicks and burrs nearly as well as it can for me.

I've got some knives I've sharpened with guides, and their included angles are 25-30 degrees and can whittle hair--a little less gracefully than some edges I've seen, but they do it. Anyway, they don't go through the TP I've tried, and I've tried several--that's all I'm going to say about that.

 

[spyken]

hair whittling for polished edges...good for push cuts, not slices.

I like shaving/paper slicing and cutting fabric rolled up in a ball for grabby slicey edges.

but they only test the sharpness of the knife, not the edgeholding.

 

[Ankerson]

Type of TP is very important here and personally I think this kind of sharpness will only be seen on something that holds perfect angles.

I question TP as a test because that type of cut can be made with a edge from a 600 or 1200 mesh diamond hone. Also any time I've ever tried the TP test after polishing a edge it would only glide on the TP and I'm talking about polished edges that will pass a HHT.

So its either a factor of the TP or the fact a guided device like the EP will produce a sharper point than any hand sharpening can compare too because of its perfectly set bevel angles.

What is your included bevel angles on the knives capable of the TP cut?

It can do it at 30 degrees or 40 degrees inclusive, angle really doesn't matter that much as long as it's not crazy.

I think you hit it when you talked about the EP and set bevels, the edge is so refined it slices right through the TP.

The 6000 grit EP Tapes are .5 Micron or less.

 

[mmarkh]

How long will a steel like S30v hold an edge like that? Once it will slice TP if you cut some other stuff like veggies will the TP slicing edge hold for long? I use arm shaving as my sharpness standard and my knives can hold that for quite a while. I wouldn't mind taking my edges to the next level but I don't want to have to constantly sharpen them. I hand sharpen with stones then I strop to sharpen my knives. I have been thinking of getting an Edge Pro but am afraid of the nasty scratches I have seen some people put on their knives with them.