Knives can shave but cant don't cut paper...

[bmilla35]

Well, I started sharpening on my paper wheels recently and surprisingly had good results very early. I've successfully sharpened two knives barely suitable for cutting butter to the point where they cleanly cut the hair off my arm. As a result, my arm looks ridiculous lol.

So, seeing these results I decided to cut some paper, a function i realize serves virtually no purpose other than proving sharpness. I COULD NOT CUT IT AT ALL. Why is this?

I think a call to Richard J is warranted anyways, but I was just curious as to what you think. Thanks for your insight!

 

[cbwoods67]

Were you slicing or push cutting? If the edge is taken to a high polish, it may just drag across the paper when slicing and seem dull, but go through like a laser with a push cut.

 

[Obsessed with Edges]

At least a couple possibilities:

1.) A wire edge can shave hair like a razor, but will fold over quickly in anything tougher, like paper, cardboard, etc. And more often than not, a 'shaving' wire edge will only do so in one direction, because it leans to one side (into the skin, which effectively traps hairs and is able to cut them). If the blade is turned over, it often won't shave, because the wire edge is curled up & away from the skin.

2.) Cutting paper utilizes more of the edge's length, assuming a slicing or draw cut. Shaving hair involves only a very short section of the edge (at least wide enough to cut one hair). I've had a lot of knives that appeared to shave well, but usually only in relatively small portions of the edge's length. It's a deceptive 'test' for a blade. Focus on making sure the entire edge will slice paper first, and use a magnifier & bright light to inspect areas that don't. Usually, if so, there'll either be a wire edge/burr at the poorly-performing section, or the edge isn't yet fully apexed in those areas.

For the above reasons, I don't put too much emphasis on seeing if the edge will shave. I've found that if it slices paper well, using the full length of the cutting edge, the edge is in good/excellent shape for any other real-world cutting tasks. If it just happens to shave well in addition to that, so much the better. But don't worry too much if it doesn't shave (unless it's a shaving razor, of course ).

 

[HeavyHanded]

Check to see if your edge has become overly broad. In my experience this is the number one reason for that sort of performance. The edge is fine and clean, but obtuse - will shave but has very little efficiency for tasks requiring a deeper cut.

Another factor - not all hair is created equal - I can shave the hair off my calf with a ridiculously coarse edge, but my (much finer) arm hair needs a lot more refinement.

 

[Obsessed with Edges]

Check to see if your edge has become overly broad. In my experience this is the number one reason for that sort of performance. The edge is fine and clean, but obtuse - will shave but has very little efficiency for tasks requiring a deeper cut.

Another factor - not all hair is created equal - I can shave the hair off my calf with a ridiculously coarse edge, but my (much finer) arm hair needs a lot more refinement.

Same for me. And the hair on the back of my neck is even finer still.

 

[richard j]

i'll give you a call later today. i have push cut paper with obtuse edges done on the wheels plus shave arm hair with the same edge. i have also had an 80 grit edge treetop armhairs so there might be something else wrong. i had trouble cutting some paper one day only to find out the paper was damp even though it felt dry from too much humidity in the air.

 

[Bill Hoffman]

Yup, damp paper will drive you nuts wondering what
happened to your edge.:grumpy:

Bill

 

[dorpmuller]

Watching this with interest-I'm a complete newbie with sharpening.

What's the best standard issue paper for test cutting?

I am finding the whole sharpening/stropping arena a very interesting subject BTW. Practicing on a couple of $5.00 China knives before I touch anything good.

Rich

 

[TheSharpStuff]

welcome to my world
:megusta:

 

[Obsessed with Edges]

Watching this with interest-I'm a complete newbie with sharpening.

What's the best standard issue paper for test cutting?

I am finding the whole sharpening/stropping arena a very interesting subject BTW. Practicing on a couple of $5.00 China knives before I touch anything good.

Rich

I like to use phone book paper. It's quite plentiful, with a guaranteed 'new supply' with each new calendar year. No need to turn the old ones in; I do MY OWN version of 'recycling' these. And it's also thin enough to be a good test for a blade. Even very tiny burrs, nicks or wire edges will snag enough to make the paper fold over when cutting, so it becomes immediately apparent where those defects are on the edge. It's also fun to occasionally see just how deep a blade will slice into a whole phone book, and with how little effort.

Mail-order catalogs are also pretty good, for the same reasons. Christmas season is upon us, so my supply of those is forecast to rise a bit.

 

[Ray86]

i'll give you a call later today. i have push cut paper with obtuse edges done on the wheels plus shave arm hair with the same edge. i have also had an 80 grit edge treetop armhairs so there might be something else wrong. i had trouble cutting some paper one day only to find out the paper was damp even though it felt dry from too much humidity in the air.

I just sharpened a knife on my kme sharpening system. It will shave my entire arm but will not cut paper. I don't see a bur or anything on it. I can't figure it out.

 

[000Robert]

I just sharpened a knife on my kme sharpening system. It will shave my entire arm but will not cut paper. I don't see a bur or anything on it. I can't figure it out.

Test for a burr with a piece of folded paper towel, that's what I use. If there is a burr it will catch on the paper towel.

 

[P_A_S_1]

I just sharpened a knife on my kme sharpening system. It will shave my entire arm but will not cut paper. I don't see a bur or anything on it. I can't figure it out.

I find that after sharpening a light steeling aligns the edge in a way that I can't get coming off a stone even with light strokes.

 

[gamma_nyc]

I find that after sharpening a light steeling aligns the edge in a way that I can't get coming off a stone even with light strokes.

I find the same trick helps me.

As for finding the burr, someone turned me onto this years ago - use your fingernail to slide down the blade from the shoulder to the edge . You’ll be able to feel the catch of a burr on your nail. Careful though!

Also, a jeweler’s loop is a great magnifying glass for that sort of detail. It’s especially helpful if you mark up your edge with a sharpie before sharpening. Good luck!

 

[Obsessed with Edges]

I just sharpened a knife on my kme sharpening system. It will shave my entire arm but will not cut paper. I don't see a bur or anything on it. I can't figure it out.

That's a burr or 'wire edge'. Also sometimes called a 'foil edge' - it can literally look like metal foil under high magnification, and will be just as flimsy. It's possible it's small enough, you won't actually see it by naked eye or even feel it with fingernail tests. But the fact it can't cut paper, but shaves, is key. It means the apex is too thin & unstable to stand up to anything more than shaving hair. And that instability is almost always due to the presence of a very thin, flimsy burr at the apex, which folds over or moves back & forth under the 'load' of paper cutting. Picture below shows one of those wire/foil edges, part of which is stripped away from the edge, leaving more stable steel at the apex. The part that remains attached has that crinkled 'foil' look to it - hence the term 'foil edge'.

If it shaved your arm - then test to see if it'll shave the other arm, with the blade flipped to the other side. If a burr is on the edge, it'll likely be bent or folded slightly to one side or the other. When it's leaning downward into the arm being shaved, it'll cut the hair. But with the blade turned the other way (opposite side toward the arm), you might see it won't shave well, if at all. That's because the burr is then leaning up & away from the arm and the hair will just deflect away from contact without being cut. That's an easy way to detect the presence of a burr, if you can't otherwise see it or feel it.

And if the burr is that flimsy - then try a few cuts into wood or some heavy cardboard. That'll either strip the burr away completely, leaving more stable steel at the apex, OR it'll fold the burr completely over, which essentially mimics a rounded ('dull') apex. Stripping the burr away will likely leave the edge stronger, more stable and better able to cut paper. But folding the burr over, without removing it, will leave the edge very 'dull' and incapable of cutting anything. With either change seen, it's confirmation of what's going on.

 

[Blues]

Foiled again!

 

[Sharp Steel]

I like to use phone book paper. It's quite plentiful, with a guaranteed 'new supply' with each new calendar year. No need to turn the old ones in; I do MY OWN version of 'recycling' these. And it's also thin enough to be a good test for a blade. Even very tiny burrs, nicks or wire edges will snag enough to make the paper fold over when cutting, so it becomes immediately apparent where those defects are on the edge. It's also fun to occasionally see just how deep a blade will slice into a whole phone book, and with how little effort.

Mail-order catalogs are also pretty good, for the same reasons. Christmas season is upon us, so my supply of those is forecast to rise a bit.

I have not received a phone book in years, and the ones they were giving out were a small section of yellow pages. The closest I get to usable paper for cutting tests are the weekly advertisements for the supermarkets and drug stores. Everything is so Internet centered these days. If you want to find a plumber you have to hit one of the search engines instead of grabbing the phone book.

Reviews can be gamed through "search engine optimization" so they are hard to trust too.

I always felt that shaving hair was a crude test for sharpness, because even a dull razor will shave, but it will tear your face to shreds doing it.

 

[67RS/SSx2]

Very nice and telling visual. What magnification is this? I need to get some type of magnifier to better see my edges.

 

[Blade Lab]

Rolling papers are a good test for sharp edges. They're cheap and consistently the same thickness. If you can slice a rolling paper lengthwise, you have a very sharp edge. If you can slice it in the short direction you have a razor-sharp edge.

 

[Obsessed with Edges]

Very nice and telling visual. What magnification is this? I need to get some type of magnifier to better see my edges.

I was using a USB microscope. Offhand, I don't know at what magnification it was set when the picture was taken. But I think most of them advertise capability up to 200X - 400X range. I think the picture might've been taken at something lower than that. Focus, lighting and depth of field get very, very difficult to manage at something higher than that - it's very fussy setting it up. By the naked eye, the portion of the burr that separated from the edge resembled a fine fiber or hair, seen only under bright light. The blade was positioned underneath a lamp when I noticed it - otherwise I might've overlooked it. I'd thought initially it was a fiber from a microfiber towel I'd used to wipe down the blade - but it didn't just brush off, when I attempted that.