Scary sharp blade really worth it?

R

realitycheck

Joined
Nov 24, 2007
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Alright guys I have another question. I hear people talk about getting their knives so sharp that they can cut free hanging hair, slice toilet paper, tree top hair, w/e other ones you want to add to it that says a knife really is scary sharp. I also read people saying that the edge is actually not useful in real life situations. Cutting cardboard, zip ties, plastic tie straps so on and so forth, that once you try and use that edge on these things that it just rolls over and the edge is no where near as sharp. Is this true, or not??
 
when it comes to durability, alot rests on how thick the edge is. if there is alot of metal behind it, it will be more stable. if it is a finely pointed triangle, it will more easily roll over and dull.

the trick is to find a good balance of thickness that allows you to cut well but to also retain the edge without rolling and chipping. i have got my mora so thin before that it deformed doing some light slicing on clear maple. i didn't like that so i thickened the edge up and now it is still thin, but not so thin that it will be damaged too easily. many modern knives have a fairly thick edge for my tastes, so i usually back-bevel them to thin them out.

even thick-edged knives can get scary sharp. i could make a scary sharp 90 degree angle if i really wanted to, but it would not cut very well.

if you have a scary sharp edge, and it is burr-free, then it will stay sharp for a while, as long as you are not abusing it. it will lose that scary sharp, but then it will still be shaving sharp, and then it will degrade to hair-scraping sharp, and then it will degrade to just sharp, and so on until butterknife-dull, if you let it get that far. if you start with a knife that is just sharp, you will get to dull a whole lot faster.
 
Alright next question. When you have a knife that is shaving sharp. Then you take it to hair popping sharp. Does that edge tend to bite into your skin more?? I feel like so far the sharper I get the more it seems to bite and it doesnt just slide across the skin. Is this right or do I have it backwards??
 
Sounds reasonable that it would bite more when sharper. I carry a Kershaw Vapor that I rebeveled so that when sharpening on the Spyderco Sharpmaker using the 20 degree/side slots, only a small microbevel is formed. I've been sharpening it that way for about 3 months now and the actual edge bevel is still just a thin line on the edge. What this does is allow me to maintain an edge that will cut a free hanging long hair without spending an hour to resharpen it. 10 to 15 swipes per side on the medium rods and its back to hair parting sharpness. I find that polished, hair popping edges last a good while for me, and the Sharpmaker treatment keeps it that way easily. In short, thinner edges hold an edge longer, right up to point where they start to take damage. My kitchen knives will cut for a very long time, given the edge is 24-30 degrees total and the steel is relatively soft. I keep them sharp with the Sharpmaker at 15 degrees per side. All that fine cutting ability goes out the window with a trip through the dishwasher. To withstand that, I'd need a 20-25 degree per side bevel, and even then some damage would still happen.
 
Me2 on your vapor, do you just use the medium rods and have an edge that will split a free hanging hair?? Or do you use something else also??
 
Just the flats on the medium rods. It will cut a long (>6") hair hanging from between my fingers, like the free hanging rope test, but with hair. A light touch on the fine rod flats will do even better, but I rarely bother just to save some time.

Just to be clear, since I dont think I was in the earlier post, I think this type of edge is worth it and can be maintained quickly, as long as the edge isnt taking damage during use. I used the thinned edge to scrape/pry a flake off some cast iron pipe once, and had to return to the belt sander to remove the damage. Of course, I just sharpened over the small chip that developed for 2 months before doing that.
 
I. Sharp edge need more time to get dull then not sharp edge - sorry if I just sad too obvious thing.
II. Super-Sharp edge is different then small angle edge. All my edge is 30 degree not smaller. It is just close to ideal triangular then duller edge, but angle is same and so it is as strong as not so ideal triangular.

I actually think it may last longer just because sides are more flat and so it has less friction when moves into target, while more rough surface will lose particles faster...

Thanks, Vassili.
 
My "scary-sharp" edges last long enough on cardboard and all-plastic zip-ties as well as cutting down blister packs. Sharper edges are reserved for the kitchen where they only see food and a cutting board.

It's all a balance. You can have an edge thick enough to withstand daily cutting also be sharp enough to whittle hair - a lot of folks thin their blades out to 10 degrees per side and add a 15 degree microbevel on each side. That leaves plenty of meat behind the edge for lots of hard cutting while still being thin enough to make that cutting enjoyable and the edge scary sharp or sharper.
 
really, really sharp edges don't stay really, really sharp very long, but they will still be really sharp for a good while, then sharp, and then dull eventually. The sharpness level is delicate, but it doesn't go dull immediately like you might suspect.
 
realitycheck said:
... I also read people saying that the edge is actually not useful in real life situations. Cutting cardboard, zip ties, plastic tie straps so on and so forth, that once you try and use that edge on these things that it just rolls over and the edge is no where near as sharp. Is this true, or not??
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Apart from the effects of having a thin versus thick edge, a scary sharp edge requires finer and finer abrasion and thus a more polished edge. A polished edge is not useless in real life, it is just more suited for certain tasks. A polished edge is better for pushing through harder materials such as carving wood, and I believe cutting plastic. Edges finished with coarser abrasives have a jagged edge that act as serrations to grab and slice fibrous materials like rope. I'm not sure whether a coarse edge or a fine edge is better for cutting cardboard as often cutting cardboard is a combination of pushing and slicing.
 
My reply to a similar question on another forum:

There are those who sharpen just enough to get the job done.

There are those to whome sharpening is the hobby and there is no end to tinkering and aquiring equipment and stones to take an edge to the next level.

Then there is somewhere in between.

I am somewhere in between. I can get a blade sharp enough to do the job and then take refine it a little more. I like to fish, hunt, cook... My knives are all working knives. No safe queens or blades that get sharpened just to sharpen them and then sit.

You can take it any direction you choose.
 
Agree with what most have said, as a general rule the finer the edge, the better the edge retention will be, all other things being equal. A good part of this IMO has to do with the necessary care required to obtain that truly fine, scary sharp edge in the first place, which can only be realized by producing as little damage as possible to the steel during the sharpening process.

However I would also say that there probably is a point-of-no-return, practically speaking, in terms of time and effort required to achieve an even sharper edge versus time and effort required to resharpen to the same level you started out with. For example, you can probably get a better edge by going to the trouble of setting up your Edge Pro and polishing the microbeveled edge with the fine tape than you would get with a few light passes on a Sharpmaker using the white rods. But since the Sharpmaker is probably going to be a lot handier and only take a few seconds to restore the edge, finishing with the Edge Pro may not make good sense in some circumstances such as doing extended work while on a job or in the field.
 
Nosetotail said:
Apart from the effects of having a thin versus thick edge, a scary sharp edge requires finer and finer abrasion and thus a more polished edge. A polished edge is not useless in real life, it is just more suited for certain tasks. A polished edge is better for pushing through harder materials such as carving wood, and I believe cutting plastic. Edges finished with coarser abrasives have a jagged edge that act as serrations to grab and slice fibrous materials like rope.
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I agree %100. I just had a little vacation time and was bored so I put together a strop (inspired by nozh2002’s videos) and got my knife sharp enough to whittle hair. I was proud of it. It could shave hair without touching the skin. When I got back I showed a few people at work and then used it the first time to cut away some rope like material that's inside of the cable I work on and got laughed at. The polished edge was useless. For what I use my knife for I prefer a non-polished edge. I did however sharpen a paring knife the same way and it works very well for slicing veggies peeling potatoes.
 
Serration does not work better on rope. Serration is only good to keep knife able to cut even without any maintenance. To me the idea that rough edge do something better then polished need yet to be proven.

I think that people had rounded edge after polishing it without too much skills and that make them think that rough edge better then polished.

After sharpening on medium abrasive you may shave you hand, after polishing it edge may became actually duller - I saw this with my sharpness thread test, but continue to shave. So in this case polished edge will last less then rough one, but not because it has no teeth but because it is rounded.

If anybody can explain how to do experiment to test it - please tell, me. I heard before something about rolled up tobacco paper, but with search function switched off can not reach it.

Thanks, Vassili.
 
byersj79 said:
I agree %100. I just had a little vacation time and was bored so I put together a strop (inspired by nozh2002’s videos) and got my knife sharp enough to whittle hair. I was proud of it. It could shave hair without touching the skin. When I got back I showed a few people at work and then used it the first time to cut away some rope like material that's inside of the cable I work on and got laughed at. The polished edge was useless. For what I use my knife for I prefer a non-polished edge. I did however sharpen a paring knife the same way and it works very well for slicing veggies peeling potatoes.
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Well I cut quite a bit of rope with my polished edge. I can assure you it cut rope very well!

Thanks, Vassili.
 
Super sharp edge do not need to much pressure to cut skin, so I was able to cut out splinters without drop of blood. I gently cut skin right on top of splinter and take it out if it will not fall out itself. This is impossible with shaving sharp knives - they require more force to cut and so actually push splinter in.

Also I cut some leather making sheath - because less force needed to cut - cut became much more accurate and pleasant.

There are many thing which can be done with really sharp knife, this is again matter of what you get used too. If you get used to do certain things with you knife then making it sharper do not really needed, it works already, but something you just can not do without really sharp knife.

I hope other members also have examples when good sharpness really needed.

Thanks, Vassili.
 
nozh2002 said:
Serration does not work better on rope. Serration is only good to keep knife able to cut even without any maintenance. To me the idea that rough edge do something better then polished need yet to be proven.
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I'd disagree. However, it does depend on how you use a knife and what you cut. I've prooved to myself witch type and grit works best but that doesn't mean it is the right level of polish for you or someone else. In fact what one person calls polished could be anothers coarse edge. At what grit would you call an edge polished and what grit is coarse/rough?
I think that people had rounded edge after polishing it without too much skills and that make them think that rough edge better then polished.After sharpening on medium abrasive you may shave you hand, after polishing it edge may became actually duller - I saw this with my sharpness thread test, but continue to shave.
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I think you are correct with that. I beleive alot of people round their edges and think they polished them when they really have dulled them.
If anybody can explain how to do experiment to test it - please tell, me. I heard before something about rolled up tobacco paper, but with search function switched off can not reach it.

Thanks, Vassili.
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Are you thinking about a tightly rolled up paper towel then you slice across it to cut it and use very little pressure pushing down to prevent a push cut?
 
I like them sharp enough to make cutting easy. Thats all it takes. Save some edge for another day. Shaving sharp is plenty.
 
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