Scary sharp blade really worth it?

[thombrogan]

Whenever I think I can sharpen, I re-read Vassili's posts to remember I can't.

I would not/do not/cannot blame a polished edge for not cutting rope or cable. I would/do/can blame a rounded over polished edge for not cutting rope or cable. And you can, too!

 

[hardheart]

for rope cutting, it depends on expectations with technique. The toothier edge will do ok for a long draw and little downward pressure. If you try that with a high polish, you won't get very far. The polished edge pushcuts much better, so pushcut the rope.

 

[Andrew Colglazier]

I like a fine edge for fine work such as food prep.

I like a decent edge for heavier work, doesn't need to be shaving sharp, just sharp enough to get the work done.

I find that I have no need for fancy sharpening systems and what not. I don't use strops, etc.

If an edge is really dull, I use my belt grinder to reform the bevel and thin the edge. Once the edge is again sharpenable, I use a big, antique butcher's steel, followed up by polishing on a big ceramic rod. Any stropping is done on my pant leg.

I find that this produces sharpness completely adequate for anything I might need, a bit short of shaving my face, perhaps, depending on the thickness of the blade.

Andy

 

[dantzk8]

Serration does not work better on rope.

Yes if you pushcut. No, if you slice.

Serration is only good to keep knife able to cut even without any maintenance.

True.

To me the idea that rough edge do something better then polished need yet to be proven.

A coarse edge will slice a ripe tomato. A polished edge will pushcut hardwood.

dantzk.

 

[nozh2002]

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?

Yes, something like this - can you explain it step by step and what does show this difference?

Thanks, Vassili.

 

[nozh2002]

Whenever I think I can sharpen, I re-read Vassili's posts to remember I can't.

I would not/do not/cannot blame a polished edge for not cutting rope or cable. I would/do/can blame a rounded over polished edge for not cutting rope or cable. And you can, too!

Sorry, I Russian English is my second language, and too sophisticated English is to hard to understand to me. What is your point?

Thanks, Vassili.

 

[Vivi]

The sharper the better in my opinion. If you take the secondary bevel of a knife to an acute angle and then use microbevels, getting a "scary sharp" edge can take less than a minute. I'll set the bevels with a diamond stone, then once the knife needs touched up I use a ceramic rod and a strop, about 20 passes on each and I'm done. Nothing to setup, no guides or contraptions, just a sharp edge in a practical time frame. I can get a sharper edge if I really want to, but as long as its sharp enough to catch hair above the skin I'm content.

 

[nozh2002]

Yes if you pushcut. No, if you slice.
A coarse edge will slice a ripe tomato. A polished edge will pushcut hardwood.

dantzk.

I can not understand why super -sharp edge will not perform slice? All my knifes perform slices very well much better then serration. Cut is very clean and it take much less force to go though target.

Especially it is noticable on ropes - I need to apply more force to slice manila rope wit serration than with super sharp-edge.

Actually all my tests if you see video have slice move not push - it is limited to 1" but it is not push cut.

Thanks, Vassili.

 

[hardheart]

well, a 1" slice on 1/2" rope is different than doing a full length slice with a 5" blade on that rope. At a 1/2" of pull, you expect a 1/4" depth of cut, half the slice, half the material cut. Or at a 1/2" of pull you expect a 1/20" depth of cut, a tenth of the slice, a tenth of the material cut.

 

[nozh2002]

well, a 1" slice on 1/2" rope is different than doing a full length slice with a 5" blade on that rope. At a 1/2" of pull, you expect a 1/4" depth of cut, half the slice, half the material cut. Or at a 1/2" of pull you expect a 1/20" depth of cut, a tenth of the slice, a tenth of the material cut.

Sure, I was talking about full length slice not only about slices I use during testing. I just mention that in my tests where I cut 800 times manila rope with supersharp edge it was not pushcuts.

But let me try it. If there is some way to expose this difference I will love to do this test to see how rough edge stand against properly polished edge.

Thanks, Vassili.

 

[hardheart]

What I would say is noticeable is the way the rougher edge doesn't require as much extra force to be applied as the draw is made. The 'tooth' of the edge grabs the material and cuts into it, and since that tooth is along the edge, it continuously performs this with the same downward force along the draw. A highly polished edge will cut a certain depth for the force applied, and drawing it laterally doesn't change the effect much because the edge is so smooth it is acting as if there isn't a change in the contact area.

If on a magnified image you get toothy-toothy-toothy-toothy-etc. Then on a draw you get that grab/sever-grab/sever-grab/sever. If its smooth-smooth-smooth, then you get that initial cut depth for the downward force, but the draw keeps presenting that same smooth edge. So if you don't add even more force, you won't get deeper cutting because the geometry of the blade above the edge is demanding more force to part the material sufficiently to let the pressure at the edge be maintained

At least this is my guess on why toothy edges work better on long draws on fibrous materials..

 

[HoB]

Serration does not work better on rope.

It depends of course on the rope, but in general: yes they do. Try free-hanging (in a pulling motion, on a ship you don't have a cutting surface to cut a line on) 2" nylon rope. Nearly impossible with a PE blade, best is of course a serrated hawkbill or at least a wharncliff. The harder and slicker the rope material and the larger the rope diameter the greater the advantage for the serrated blade. Worst case scenario: large diameter polypropylene rope.

IIRC a coast guard member (it might have been a fisherman, its been a time since Sal posted some stories that people had sent in to Spyderco) used a Spyderco Rescue to cut through (or shall I say: saw) a 2" steel re-inforced nylon rope to save his leg. Of course the edge was gone, but the leg wasn't.

 

[db]

Quote:
Originally Posted by db
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?

Yes, something like this - can you explain it step by step and what does show this difference?

Thanks, Vassili.

I'll try.
1 tightly roll up a paper towel, you can even twist it to get it tighter if you want.
2 Cut across it with a slicing motion. I do heal to tip for a direction. Don't press down you are trying not to press cut.
You should easily notice a difference between a coarse, medium, and fine edge.

 

[me2]

utility edge is best, unless you are a japanese chef or shaving.

Care to elaborate? What do you consider a utility edge?

 

[theonew]

Here's my take. Just using an ultra-fine ceramic rod I've been able to get all of my knives to somewhere between 30 and 40 grams using Vassili's scale below.

If you just able to cut hair by gentely touching it (touching it as it shown on video) - it is about 40 g sharpness.
Next level - you split hair - kind of longf diagonal cut - it is about 30g sarpness.
Finally - whittling hair with long shave - 20g. The best sharpness I see so far.

It doesn't take very long, unless the edge is really degraded, but does require a very light touch. Now using a strop I'm sure I could make it sharper but if you look at Vassili's chart in this thread it appears that a 20g edge becomes a 30 - 40g edge after only one or two cuts, so that to me is where the extra effort outweighs the benefit.

 

[nozh2002]

... after only one or two cuts, so that to me is where the extra effort outweighs the benefit...

I should add one or two cuts of 1/2" manila rope.

2 HoB

It is about keeping working condition for longer, because serration will continue to tear up rope even if it is get duller. 2" steel reinforced nylon rope is perfect example - PE which get dull in the middle of rope will be useless to finish the job - no matter how hard you will try, but serrated with same edge condition will continue to work until it's done.

This makes perfect sense. I just look from different point of view - if the load is different then 2" steel reinforced nylon rope.

2 db

Thank you. I'll try.

Thanks, Vassili.

 

[Nosetotail]

I prefer to use someone else knife if I have to cut anything reinforced with steel, or the Kevlar rope we use at work.

 

[thombrogan]

Sorry, I Russian English is my second language, and too sophisticated English is to hard to understand to me. What is your point?

My point was that you sharpen better than me.

Care to elaborate? What do you consider a utility edge?

Not going for something finer after stropping on 1 micron polishing paper.

I prefer to use someone else knife if I have to cut anything reinforced with steel, or the Kevlar rope we use at work.

Good answer!

 

[nozh2002]

I just resharpened my RatTrap - usual way, without removing burr in the process - just continue with finer grit when I have full loength burr on each side. Again burr in this case just became thinner and thinner fron grit to grit. I stop at DMT Extra Fine. I finally get rid of burr without raising angle but by moving blade same way under same angle with no pressure but knife weight only, changing sides after each pass. It take may be 20-30 passes, but it eliminates burr.

I try to whittle hair with it - not working, but I see it bumping on hair shells. I guess, this is indication of the teeth on the very edge. But it chops hair when blade hit it moving and not really to fast. I also try to cut toilet paper - it does not cut it at all. I tried to chop hanging toilet paper - it chops it pretty well, even better then polished edge.

I compare it to polished edge blade (just tested to be able to whittle hair).

Swamp Rat "Rat Trap" - 4.32oz 122.6g - CPM S30V
Microtech "SOCOM Elite" - 4.29oz 121.8g - CPM S90V

http://www.youtube.com/watch?v=eCcbyJLAGAw

In result, as you may see on the video, toothed edge bites better - it cuts about twice then polished edge.

This is experimental prove that I was wrong, thinking that polished edge will be as good as toothed in draw cut. But now there is no doubt about functional - practical difference between this two types of edges, one for push cuts, another for draw cuts.

Thanks, Vassili.

 

[theonew]

Try a much faster draw cut.