Edge Microchips and Performance

[Cypress]

I try to keep the edge on my knives tip-top. I go through a series of diamond stones on my Lansky, a ceramic stone for polishing, then a loaded strop, and finally, bare leather. This makes for an edge that can easily whittle hair, and I've gotten a few of them to drop-cut single pieces of hair.

One way I check my edges, is by running the tip of my fingernail down the edge in an attempt to detect chips or rough spots. Once I'm done with my sharpening routine, the edge is immaculate. My edges are completely smooth in relation to the rest of the edge, ie: A coarse edge feels uniformly coarse from choil to tip, and a polished edge is glass-smooth choil to tip, with zero "catches".

My boggle comes from this: I will use my knife for something mundane like cutting a small cardboard box into 4 pieces for recycling, but afterwards the smooth edge now has little bits that catch my fingernail. This implies I've somehow damaged the edge. This happens on my M390 Benchmades, S30V Spydercos, etc. I tend to run my nicer steels at 34º inclusive, unless it's a hard-use knife.

I'm fairly certain I don't have wire edges after being so thorough in my sharpening methods. I have a few 40x jewelers loupes coming in the mail any day now, but I'd like input from you pro's.

Questions:

1: What are these "catches" that I'm feeling?

2: Are these detrimental to the actual edge performance?

3: Recommendations as to how I can prevent this from occurring if it is detrimental?

 

[BluntCut MetalWorks]

Before going deep, let's start with - please use a freshly polished edge to make 10 slices against newsprint. Afterward, does this edge still smoothly slice newsprint without catches?

A shot in the dark. Burnishing from ceramic (depend on pressure & technique) can be detrimental/degradation to an edge of high alloy knife.

 

[Cypress]

Rolled newsprint, or flat sheet?

 

[BluntCut MetalWorks]

single flat piece.

Rolled newsprint, or flat sheet?

 

[Jason B.]

It's normal damage. The finer and smoother a edge becomes the easier it is to notice damage. Cardboard is some pretty tough stuff too and not the best to test a edge with unless dulling the edge is the goal.

 

[BluntCut MetalWorks]

I just hacked around 20ft of 3/16" thick cardboard with my little 3" 20cv/m390 fixed blade at ~26*inclusive bevel. Afterward, my nail doesn't catches the edge. Yes, it did dulled tiny bit but still slice newsprint ok.

It's normal damage. The finer and smoother a edge becomes the easier it is to notice damage. Cardboard is some pretty tough stuff too and not the best to test a edge with unless dulling the edge is the goal.

 

[Jason B.]

Cardboard is so inconsistent that any one test is a completely random sample. I've had some that you could slice all day and not cause the slightest of damage while others would completely dull the edge in one slice.

Test mediums, such as Manila rope are much better to use because they induce a consistent and constant wear to the edge. It's consistent enough to show repeatable results unlike cardboard.

Cypress,

A coarser edge is going to perform better on a high alloy steel when cutting abrasive materials. Finish in the 15-20 micron range and repeat the test. You will find less damage or better put less noticeable damage to the cutting edge.

 

[HeavyHanded]

Cypress,

A coarser edge is going to perform better on a high alloy steel when cutting abrasive materials. Finish in the 15-20 micron range and repeat the test. You will find less damage or better put less noticeable damage to the cutting edge.

This ^. There have been many reasonably well controlled tests run by a number of forum members (Ankerson, David Martin among others) that have shown notable improvements in longevity by sharpening these steels to a lower finish. They can be polished up to a very high shine, but seems to run counter to their nature. You wouldn't put a toothy edge on a high RC carbon steel, best practices with the higher VC steels seems to be a somewhat rougher finish. Cutting the cardboard at a bit of an angle will help with longevity as well - allows a cut with less pressure. Grades of cardboard run all over the map. At my workplace we get a lot of materials in using double and triple wall - even my Stanley #99 has trouble with some of them.

 

[Cypress]

A coarse edge does seem counterintuitive to high-end steel, but I'll give that a whirl.

What is happening on the microscopic level with a mirrored finish? Carbides breaking off?

 

[Jason B.]

Nope, it's you just notice it. With a edge that has no defects or distortions once you induce defects or distortions it is VERY obvious. Like a mirror polished blade vs a stone washed blade, one shows every spec of dust the other hardly shows a scratch.

 

[Ernie1980]

Nope, it's you just notice it. With a edge that has no defects or distortions once you induce defects or distortions it is VERY obvious. Like a mirror polished blade vs a stone washed blade, one shows every spec of dust the other hardly shows a scratch.

Excellent comparison! I have experimented with different finishes with different steels, and am starting to see where my knives preform best.

 

[HeavyHanded]

A coarse edge does seem counterintuitive to high-end steel, but I'll give that a whirl.

What is happening on the microscopic level with a mirrored finish? Carbides breaking off?

I'm not sure, but will take some micrographs of edge wear at some point in the future. Is possible the carbides release more easily when their attachment points get thinned out, sort of like teeth getting some mobility when the bone recedes. Might be my imagination because I've done absolutely zero controlled testing, but I'd swear my carbon steel blades in 58-60RC hold a fine edge better than the high carbide stuff - a condition I cannot imagine without the carbides pulling out - they aren't going to break off or fracture under normal use faster than a carbon edge will dull. Left at the 15-20u range the high carbide stuff will just keep cutting long after (most) carbon steels will throw in the towel at a similar finish.