Recommendation? how sharp my knife should be?

J

Jake Dawson

Joined
Jul 19, 2020
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21
what im basically asking is: "should every knife i own be able to slice paper"?
what i have right now is sharpening stone (wetstone) and one of those cheap knife sharpeners with spinning gears inside.
(spoiler alert: im bad at sharpening however i can make coarse blades sharper)

i noticed that its very easy to get from razor sharp to > coarse if you use your EDC knife on a casual basis (once a day or so). i own 4 knives and they are all in the 20-50$ range.
2 of them are able to cut paper, but the other 2 just tear through it.

HOWEVER, i managed to sharpen my kershaw shuffle to the point where it can be sharp enough for EDC tasks, but not sharp enough to cut paper.

is the paper test simply a matter of cutlery autism so-to-speak or we should maintain our knives on a daily basis just to sort of keep the "razor" edge to it?
 
I think the basic advice is that you knife needs to be sharp enough for the tasks you put it through. I would also say as sharp as you would like it to be, but this is not always achievable.

With the carry rules here in the UK I tend to spend most of my time with kitchen knives. For those I like them to be as sharp as I can get them
 
I've liked paper-cutting in fine paper, like phonebook pages, as a fool-proof indicator that my edges will easily do everything else I want them to do. In other words, if I can make the edge cut effortlessly and repeatably through phonebook paper, then I know for certain it'll also do other things like slice a tomato easily or whittle or carve wood cleanly, cut rope, etc. It eliminates any doubts about whether my edges are sharp enough for my needs or preferences, without having to test the edge in all those other things first. Every edge I sharpen anymore gets the phonebook page cutting test, before I declare it 'good enough'. That test has never let me down.

And even in tasks where effortless paper-slicing sharpness isn't needed, you'll find that if you do take it that extra bit further, it'll do everything better than it otherwise would've. That's the 'hook' that'll goad you into sharpening to another level, in the long run. It's easy to get spoiled on such edges. And once you realize what it can do for you, it's hard to accept anything less. It becomes habit, which is good because that also makes it easier and automatic in the longer run.
 
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Paper is a pretty broad term and can mean many different types. The ability to cut those different types can define very different levels of sharpness.

In general, if you're talking about printer or notebook type paper, then really, that is pretty easy to cut. Knives with semi-decent geometry that many people here would consider dull can cut printer paper. You can discuss the cleanliness of the cut or the sound or what have you but it doesn't take a lot of edge to cut this kind of paper. For me, if a knife can't slice this kind of paper pretty easily, it needs maintenance.

Also, I don't know what kind of powered sharpener you have, but there is a very good chance that thing is tearing up your knives.
 
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If you want to find inconsistencies in the edge that you can't feel with your finger or see, then slicing magazine paper very slowly can give you some information.

My favorite is to just take one sheet of paper towel, fold it a couple times and then slice it with my knife. If it cuts paper towel easily then it also cuts onions, tomatoes and meat without problem.
 
It depends how coarse the last stone was. A 180 grit done carefully should slice copy paper. The finer stones will slice thinner paper. DM
 
Jake Dawson said:
is the paper test simply a matter of cutlery autism so-to-speak
Click to expand...

It's all up to you. What's sharp to me, might be unacceptable to someone more skilled. It's all up to the individual.

My advice would be to focus on refining your technique, maybe read some posts here for guidance, and pretty soon all your knives will be able to slice through regular paper.
 
If a knife can’t cut paper, it’s dull. If dull is fine with you, then you’ve achieved optimum sharpness (for you).

For my own knives, if they can easily cut curves in phonebook paper and shave hair they’re sharp enough for me.
 
As far as cutting paper being a good test it is a useful one especially for larger blades. By doing a long slicing cut you can find out if you have a part that isn't sharp yet, still has a burr or has developed chips. If you do a fair bit of paper testing you can get a feel for it and tell a lot from the sound, feel and what types of cuts are possible to make. Lastly you can try to see if you can cut the print off of paper without making a hole or cutting the sheet. A far more useful test is to see if you can get the edge to grab your thumbnail without pressure. Once you get your knife to this point it cuts most things well and usually it is ready to strop. Forget about using a leather strop to start off with because using something like a belt or or strap will tend to round over the edge and if you use a abrasive polish on it it is even worse. Even when leather is glued to a wooden block it can still cause the same problem if you use to much pressure and the leather squishes down. Instead just use a piece of soft wood like a paint stir stick and then loading it with some green rouge or for harder steels i use diamond lapping compound that can be purchased from a place like Amazon for a few dollars. The soft wood has enough nooks and crannies to hold the compound and is also soft enough to let the burr grab and be stripped off. You want to treat your strop just like another stone other than the fact you only use pull strokes. If you have a problem with a burr sticking hard you can give it a few more degrees like you are trying to do a micro bevel.

My recommendation for most people is to use course sharpening technique. When i first heard about it I think I was reading Jim Ankersons steel test and doubted his results because I was sure a 400 grit edge wasn't as sharp as a 4000 grit edge and the fact that the knives stayed sharp substantially longer just didn't make sense. It wasn't until I learned how to use a strop and started using a wooden one that it began to make sense. Now I use DMT course benchstone for most of my final edges. This is what they call a toothy edge. When using a large diamond stone like this so long as the edge is only dull and doesn't need major work you can take a knife from dull to being able to easily shave in about 2 minutes. If you want scary sharp this is the way to go. A more polished edge looks great but it is most of the time best for specialty uses such as wood working tools where you are only push cutting. I freehand since it is fast but everything stays the same if using a guide. Instead of using a lot of sweaping strokes trying to smooth the edge more for a given grit i simply scrub the blade back and forth imagining the i am putting more teeth into the edge. Your goal you remember is to get to the apex of the edge and you know you have done this when you can raise a small burr on the opposite side. That burr is then removed by stropping. If it is really sticking on there you can try something like pulling it through a cork or end grain on some wood or increasing your angle and using light strokes and give it a micro bevel. Grit doesn’t really play a part in this since if are say sharpening at 15 degrees per side its still 15 degrees per side no matter what grit used. There is also likely less fatigue right at the edge than when extensive finishing strokea are used. To be clear I am not nocking polished edges but I'm just highlighting that there is a difference between the two and what is best is task dependant though for general use low grit edges cut better and are just easier all the way around. If you just want to try out this type of sharpening and don't have a stone get a couple of sheets of high quality sandpaper in the 320 to 400 grit range and give it a try.

I don't know if this was the type of thing you were looking for but if it was hopefully it is helpful. If you try it let me know what you think. Or if you have problems getting it to work let me know and I will try to help. And last of all it does matter what kind of steel you use. I find that it works on all that I have tried but the best edges are going to be on harder steels. Good luck

PS. Just for reference I find a knife to be dull when it no longer easily shaves hair off my arm.
 
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Slicing Yellow Pages paper (0.002") can be a good indicator, but I prefer to sharpen
until it can push-cut that paper. There's quite a difference. There's no need to stop before you get to that point.
 
Storm W said:
As far as cutting paper being a good test it is a useful one especially for larger blades. By doing a long slicing cut you can find out if you have a part that isn't sharp yet, still has a burr or has developed chips. If you do a fair bit of paper testing you can get a feel for it and tell a lot from the sound, feel and what types of cuts are possible to make. Lastly you can try to see if you can cut the print off of paper without making a hole or cutting the sheet. A far more useful test is to see if you can get the edge to grab your thumbnail without pressure. Once you get your knife to this point it cuts most things well and usually it is ready to strop. Forget about using a leather strop to start off with because using something like a belt or or strap will tend to round over the edge and if you use a abrasive polish on it it is even worse. Even when leather is glued to a wooden block it can still cause the same problem if you use to much pressure and the leather squishes down. Instead just use a piece of soft wood like a paint stir stick and then loading it with some green rouge or for harder steels i use diamond lapping compound that can be purchased from a place like Amazon for a few dollars. The soft wood has enough nooks and crannies to hold the compound and is also soft enough to let the burr grab and be stripped off. You want to treat your strop just like another stone other than the fact you only use pull strokes. If you have a problem with a burr sticking hard you can give it a few more degrees like you are trying to do a micro bevel.

My recommendation for most people is to use course sharpening technique. When i first heard about it I think I was reading Jim Ankersons steel test and doubted his results because I was sure a 400 grit edge wasn't as sharp as a 4000 grit edge and the fact that the knives stayed sharp substantially longer just didn't make sense. It wasn't until I learned how to use a strop and started using a wooden one that it began to make sense. Now I use DMT course benchstone for most of my final edges. This is what they call a toothy edge. When using a large diamond stone like this so long as the edge is only dull and doesn't need major work you can take a knife from dull to being able to easily shave in about 2 minutes. If you want scary sharp this is the way to go. A more polished edge looks great but it is most of the time best for specialty uses such as wood working tools where you are only push cutting. I freehand since it is fast but everything stays the same if using a guide. Instead of using a lot of sweaping strokes trying to smooth the edge more for a given grit i simply scrub the blade back and forth imagining the i am putting more teeth into the edge. Your goal you remember is to get to the apex of the edge and you know you have done this when you can raise a small burr on the opposite side. That burr is then removed by stropping. If it is really sticking on there you can try something like pulling it through a cork or end grain on some wood or increasing your angle and using light strokes and give it a micro bevel. Grit doesn’t really play a part in this since if are say sharpening at 15 degrees per side its still 15 degrees per side no matter what grit used. There is also likely less fatigue right at the edge than when extensive finishing strokea are used. To be clear I am not nocking polished edges but I'm just highlighting that there is a difference between the two and what is best is task dependant though for general use low grit edges cut better and are just easier all the way around. If you just want to try out this type of sharpening and don't have a stone get a couple of sheets of high quality sandpaper in the 320 to 400 grit range and give it a try.

I don't know if this was the type of thing you were looking for but if it was hopefully it is helpful. If you try it let me know what you think. Or if you have problems getting it to work let me know and I will try to help. And last of all it does matter what kind of steel you use. I find that it works on all that I have tried but the best edges are going to be on harder steels. Good luck

PS. Just for reference I find a knife to be dull when it no longer easily shaves hair off my arm.
Click to expand...

okay thank you for the lengthy comment my man. i found that using "coarse" on my sharpener actually works. HOWEVER when i use the 'polish' or 'very fine' option it makes the blade dull again. im learning as i go.
now im able to cut paper again. not the finest cuts iv seen but its satisfactory.- no tearing or jagged rips
 
Obsessed with Edges said:
I've liked paper-cutting in fine paper, like phonebook pages, as a fool-proof indicator that my edges will easily do everything else I want them to do.
Click to expand...

I like coarse edges, from about 120 to 325 grit.

Does your sharpness test cutting fine paper apply to grits this low?

Thank you....
 
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MtnHawk1 said:
I like coarse edges, from about 120 to 325 grit.

Does your sharpness test cutting fine paper apply to grits this low?

Thank you....
Click to expand...

My favorite edges are usually finished to around 320-400 grit and I test them with the fine paper this way, always. I don't generally finish much lower in grit than 320 or so; but even if I did, I'd still be aiming for my edges to pass that same test, if possible. I've become habituated in applying that test to all my edges. And if they fall short of that mark, I tend to feel like they're not quite done yet.
 
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Paper slice in either direction, and hair shaving in either direction are my normal tests.

Fully apexed edge. Make sure there is no residual bur.
 
Obsessed with Edges, thanks!

Your cutting test for sharpness is just what I needed. I was looking for a standardized test I can reliably use with all my knives: folders, kitchen, and thicker, hard-use outdoor knives. Shaving arm hair is fun and convenient, but that's not the type of cutting I do, and I have an electric razor for my face. I've used gadgets and suggestions like a slick plastic pen at 45 deg., but since I'm not cutting anything it doesn't seem like a realistic test (not saying it isn't).

I like the feedback, including feel and sound, I get from cutting paper, and usually use notebook or scrap paper, but your test with thin paper, and good reasons for doing it, should take my sharpening to a higher level if it also works for lower grits.
 
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I like to use cash register receipt paper. It should easily slice through it.

I only wish I had kept some of the old yellow pages phone books from years gone by.
 
In the absence of phonebooks for their paper, the cash register receipt paper is a good substitute. Also the paper from most any mail-order catalog you might get in the mailbox usually fills the role. Newsprint is pretty good too, although the character of that paper is a little different sometimes.

If one REALLY wants to use phonebook pages, it's still possible to find them for free at certain times of the year at Post Offices, when the new-year editions are released. And I think some locations even put out bins to collect the old copies brought in for recycling.

We still have a landline phone at our house, so the phonebooks still get mailed to us each year and we also get local telco phonebooks dropped in our driveway. But I have to remind myself frequently, that a lot of people have abandoned their landlines and all the wonderful 'perks' that come with them (said he, facetiously ;) ).
 
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