Slicer: How much is enough?

[unit]

If we had folders with those steels at a thickness of 1mm and FFG, how fragile would these blades be?

I love this thread, man!

I can only give you the answer that applies to MY uses. I find that the overall blade thickness is less important than edge bevel, grind, and polish.

There are limits to everything, but in my use, 3 mm FFG is a good enough strength point for ZDP or VG-10, thinner than 2 mm and bending and fracturing would be more prevalent. BLADE grind angles of a certain thickness get so thick in some cases that even technique can not adequately reduce the binding between the blade shoulders and the media.

Anyone who wishes to understand this technique I speak of, simply grab the thickest piece of cardboard you can find (hopefully you can find some heavy duty stuff that looks like 2 or more normal pieces of cardboard laminated together), now make a 10 inch long (or so) cut with the knife held perpendicular to the cardboard. Now make a cut with the knife cutting at a 45 degree angle to the plane (when you are done you will have 2 sheets of cardboard that have an edge resembling a chisel). This technique will "open up" the media during the cut and reduce a lot of binding on the sides of a thicker blade. Yes, you are technically cutting a greater thickness of material by leaning the knife (particularly if the media is not porous like cardboard), but it still reduces the binding enough to demonstrate how much cut resistance is attributable to this factor.

Perhaps a lot of you guys know this, but it will save you a lot of sweat at the end of the day if you use your cutters a lot.

 

[Nebulae]

Quote:
Originally Posted by Nebulae View Post
on the other hand how much hard use do you put your knife to every day? how much battoning, or prying?

WTF? what's that got to do with this? Does this mean that you don't use your knife a lot?

Why are you now trying to turn this into a hard use vs. slicer discussion?

the only argument against thin edges seems to me to be that supper thin knives, and grinds dont have the strength required for buscraft, or other hevy duty aplications. or as somebody posted earlyer it is not devided up into axes, and razor blades, but rather a full spectrum. depending on the intended use, and other factors one can choose a thinnes to toughness ratio that serves his needes

 

[singularity35]

I also find it interesting that this topic evolves quickly into "hard use" vs "slicing" discussion wherever it is brought up. I personally think the lines between these two concepts need to be blurred a lot more than some people see them...that is just my 2 pesos though.

This may be due to the sensitivity that some people have developed because of some recent threads along those lines.

Singularity, as you and I have discussed before, I have some every day tasks that require a VERY high degree of slicing ability. I benefit greatly from a knife that will slice with the lowest amount of force so that I may reduce fatigue. It would seem that the thinnest possible blade would be the best but the slicing I do is relatively hard, so I need edge retention, and a stout enough spine to allow me to use a prying action with the knife as I cut to "open up" the media and reduce binding...therefore I need a reasonable thickness. I therefore have to compromise between the ultimate slicer and the ultimate hard user....I think a few people (upon watching what I do) would perhaps conclude that my knife (while not often regarded as a hard use knife) performs some pretty hard duties, but what is more...on paper it would seem that this knife is a fragile slicer that would fail under any sort of "real" duty.

This is also what I am interested in and hoped to discuss with this thread and the one in the other forum.

I hope this comes across right...I am not trying to start or continue any debate. To the contrary, I am trying to open some eyes to the idea that you can have a knife that performs quite well at slicing and gives up less than some may think regarding "hard use".

No worries there.

Cool thread, Singularity...this topic is right where my interests lie!

I love this thread, man!

I find it really interesting too!

I can only give you the answer that applies to MY uses. I find that the overall blade thickness is less important than edge bevel, grind, and polish.

There are limits to everything, but in my use, 3 mm FFG is a good enough strength point for ZDP or VG-10, thinner than 2 mm and bending and fracturing would be more prevalent. BLADE grind angles of a certain thickness get so thick in some cases that even technique can not adequately reduce the binding between the blade shoulders and the media.

This is the kind of experience and feedback that I was interested in hearing about.

the only argument against thin edges seems to me to be that supper thin knives, and grinds dont have the strength required for buscraft, or other hevy duty aplications. or as somebody posted earlyer it is not devided up into axes, and razor blades, but rather a full spectrum. depending on the intended use, and other factors one can choose a thinnes to toughness ratio that serves his needes

Not at all, there is no bushcraft or self defense use referred to here. I am interested to know about thin blades and slicing performance and how far they can be taken until the law of diminishing returns start to matter.

 

[Gator97]

I am trying to look at this from the present state of metallurgy.

Even in present state of metallurgy I can have 2 identical blades geometry-wise, from 2 different steels, and one would have twice or more strength than the other. I.e. I can make that one twice as thin...
My point is, in general, especially when talking about slicers, steel choice and hardness determines a lot.
That proverbial 440C or 420C at 56-58HRC will be nowhere near to CPM 10 or S110V, ZDP-189 and many others at 64-67HRC.

Yes, but we can't all have CPM 3V blades in our folders. A common steel would be say VG-10 or ZDP.

ZDP-189 is at least as rare at CPM 3V, if not more rare. And at high hardness it is more suitable for thin slicers. Because it can attain higher RC.

If we had folders with those steels at a thickness of 1mm and FFG, how fragile would these blades be?

Depends on the use. For me that 1mm thick CPM3V is more than adequate for cardboard, wood whittling, and some wire cutting too. I am very certain it will break in half if I try to pry with it, but why?

If they can take the stresses of EDC,

What is EDC stress? Obviously it varies from person to person.

But if we have to take such drastic reduction in blade strength just to see a 20 or 30 percent increase in cutting performance

Pressure = force/area. So, by reducing width twice you're multiply the force by two. I'm having hard time inserting "drastic reduction" into the formula though I figure it's more complicated than just pressure, including drag and all that, but at the very edge, that's the picture.

But in EDC where dropping a knife might mean losing more than just the tip and where the increased cutting performance in not absolutely necessary, a very fragile blade might be counter-productive.

Depends how often you drop the knives I guess. I have bunch of very high performance cutters, but I never thought to base my knife choice on the possibility of dropping it.

I am interested to know about thin blades and slicing performance and how far they can be taken until the law of diminishing returns start to matter.

Physically and anatomically, the law of diminishing returns will kick in when you can't tell the difference between the force applied for blade a and b even though one has thicker blade and edge.
Currently, if that happens it is because either the material is very soft, or knives are very dull and you have to press very hard
Otherwise, we're very long way from diminishing returns.

I dunno about EDC in generic way you mention, but I can assure you, while mincing and chopping vegetables for 2 hours straight as I do (which is nothing compared to 8-12 hour long shifts pro cooks have) I can tell the difference between 2mm and 4mm thick knives and between even 30 deg vs. 40 deg total angle. Very quickly, and at the end of that 2 hour session I feel that difference very vividly...

 

[Broos]

I look at Phil Wilson's knives and see blades optimized for slicing & cutting. Thin to win for me baby.

 

[singularity35]

Ok, I'll arbitrarily say that to be a hard cutter a knife must be able to cut tires in the same way that it was done in Unit's tire cutting videos. The cutting performance of that knife and that steel in that configuration is quite sufficient for me. That video also shows that there is enough strength in that knife so that it does not sustain any damage after the cuts.

I know that an opinel slices well, but can it do those tasks without damage? As a generic term, EDC, does not mean cutting only cardboard and whittling wood. And an EDC slicer is also not meant to pry or baton. An EDC should at least be able to handle tire cuts to be considered all around.

When a knife is only strong enough to slice food and cardboard, I would consider it a special purpose knife and not an all arounder. And besides how much better can an opinel cut over that stretch of Unit's?

 

[hardheart]

Thinness of stock of acuteness of angle are two separate things, and ffg helps no matter what the stock thickness is. Increasing width and/or spine thickness will increase bending strength, while reducing grind angle will reduce friction and have more of the applied cutting force apply to the direction parallel to the blade surface rather than being lost in effort overcoming the force perpendicular to the surface. You want the thinnest potential edge radius to concentrate your applied force into tremendous pressure to make the cut into the material, and you want the lowest grind angle to apply the most force to the cut and not the overcoming of friction. Of course increasing the width of the blade increases the area contacting the cut media, if it is a deep cut and you don't get offcut material falling to the side.

I would say there's actually too much to account for to say there is a universally superior or inferior choice in blade design. Just to cut into something, the narrowest, thinnest blade with the lowest angle will get it done the easiest/have the least friction and apply the most force to the edge. But if you need the material to fracture ahead of the edge, or keep it from 'molding' around the blade while cutting, you need to change things up.

 

[Ankerson]

It's all a trade off IMO.

The thinner the blade and the lower the edge angle the better it will slice, but the weaker the blade and the edge will be.

Something in the middle would usually be the better all around blade for EDC carry.

If one needs some kitchen knives then thinner is better to slice cheese and tomatoes etc.

For HD use thicker is better.

It just depends on what the need and use of the knife in question will be.

 

[GrinderMcgee]

A SAK can handle most my slicing needs. I have never found a hollow grind to be a hinderance in slicing and cutting performance. It is all about specific geometry.

 

[Ankerson]

A SAK can handle most my slicing needs. I have never found a hollow grind to be a hinderance in slicing and cutting performance. It is all about specific geometry.

Yeah SAK's are very thin.

 

[singularity35]

It's all a trade off IMO.

Something in the middle would usually be the better all around blade for EDC carry.

It just depends on what the need and use of the knife in question will be.

Makes a lot of sense and simple at the same time. :thumbup:

 

[me2]

For my EDC tasks, I'd say I could go very thin. Only rarely am I rough on a knife. The thinnest I'd go for hard use (for which I will use Singularity's definition) is my old Schrade Peanut. It was reground, by hand, on slack belts hooked over my spice rack and stretched out with my hand. It started out as a 1/16" thick, 2" long clip point with a full flat grind and 20 degree edge bevel. It wound up slightly thinner, 2" long, full convex from spine to edge with no secondary bevel, polished to 1500 grit wet/dry slack sandpaper then stropped. I used it in that geometry to cut electrical box size holes in sheet rock on more than one occasion, with no edge damage. It was dull, but no chips or dents had to be removed.

For normal EDC, I could get away with maybe 1/32" thick steel, maybe 1/2" wide, with a 5 degree per side convex bevel, and if the hardness was right, I doubt I'd need a secondary edge bevel. It wouldn't cut sheet rock, but with care and patience, I bet it would get through the tire.

For a real glimpse of what the minimum is, dig around for some of Alvin Johnsons kitchen utility knives. 1095, O1, and M2 with full hollow grinds, sharpened flat to the stone, with final edge bevels between 3 and 5 degrees per side. I'd pie-face my own mother out of the way for one of his trapper or stockman pocket knives with such blades on it.

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