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coarse edges

C

Cliff Stamp

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Oct 5, 1998
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In both the Buck Knives forum :

http://www.bladeforums.com/ubb/Forum27/HTML/000006.html

and in the Shop Talk forum :

http://www.bladeforums.com/ubb/Forum12/HTML/000358.html

the use of coarse edges on knives has come up and the discussion mainly wanders about which steels give the best performance and the ways in which to put a coarse edge on and how to maintain it.

Why a rough edge? Slicing performance. I had to sharpen my micra blade yesterday and I tested the performance with an x-coarse, fine and x-fine finish (DMT). The slicing performance of the x-coarse was about 5 times that of the x-fine.

I have found that softer low allow high-carbon steels take the best coarse edges and I am actually starting to lean towards them for everyday utility. The problem with many of the harder steels, especially the stainless ones, is that you can't use a file on them and an x-coarse diamond stone rips them up. These are my two favorite methods for obtaining a nice working coarse edge.

For example if you finish D2 and 5160 up to a 1200 grit DMT stone the D2 blade will be coarser, probably becuase of the Cr carbides. However if you instead sharpen both with an x-coarse DMT stone the 5160 blade is left with a rough but even finish that saws nicely into your fingernail as you run it across it, but the D2 is much more ragged and fragile. The 5160 edge can easily be steeled keeping it working for along time, but the D2 needed to be rebeveled as the microserrations tend to break off rather than fold over.

I will be getting some interesting blades soon and will be trying out various finishes on Talonite and CPM-10V and Ti. Anyone have any other interesting prospects or experience with putting a rough finish on these blades?

-Cliff
 
I am not an expert at sharpening knives by any means but, I have always prefered leaving a somewhat coarse edge instead of fine polishing, to give my microserrations effect. This way I really do not need serrations. In fact on a lot of my knives that come razor sharp like CS knives, coarse the edge up a little.

But I have found that on my hard stainless knives I cannot put a sharp coarse edge, so I have to actually go to the fine stones to finish and get a descent edge.
 
I recently posted a topic on the Spyderco
forum concerning this.I think a simi-rough
edge works best for me on Benchmade's ats-34
blades.I had tryed just about every combination of composition and grit I could
get my hands and was not satisfied.By accident , I spent more time then usual on
the brown Spyderco Sharpmaker rods.I checked it before moving to the white.The (Stryker)blade would shave clean "and" bite really hard .I was suprised to say the least.
I don't know how well it will hold up but it
cuts like a light weight McCulloch chainsaw
now.
 
Sd, brings up a good point and that is about durability. It is often stated that a high polish is much more durable than all those microserrations, I believed this for awhile as well.

However on all slicing tests I have done the opposite is true. While the little teeth probably would wear down more than a smooth polish given the same amount of wear, because the coarse edge cuts with so many fewer strokes it will actually outlast a high polish.

Now if on the other hand I do chopping and other push cutting type tests the reverse is true. So durability is not absolute but like everything else depends on what type of cutting you are doing.

-Cliff
 
Edge Geometry is probably the real factor on what cuts and what doesn't. I've cut stuff, mostly leather and the Chisel edge seems to be the one that really gets the scariest edge! When you lay a piece of leather flat and then rest the edge on top and try pushing through the flat layer of leather, not pulling across, just down, the Chisel edge (the real type chisel edge without a secondary bevel) goes through almost effortlessly while the other types will make an impression and if you draw the knife it will cut through.

My .02
G2

------------------
When a fellow says, "it ain't the money but the principle of the thing,"
it's the money.
F. McKinney Hubbard

meltingpot.fortunecity.com/haiti/688


 
I noticed something really interesting while comparing the ATS-34 and M-2 AFCKs. Not surprisingly at all, the M-2 blade would take a sharper shaving edge much more easily, but when both identical blades were sharpened at exactly the same angle on the medium Tri-Angle rods, the ATS-34 blade would bite into hard materials like wood more aggressively. I agree that edge angle is the biggest factor in cutting efficiency, but steel type is significant too!

I have found that 440C seems to provide an excellent balance between course grain structure and hardness, especially Boye Dendritic Steel (cast 440C) which will actually hold the course edge very well. Not the toughest blades in the world, but they cut like the dickens.

Harv
 
Steve, I have found that stainless blades with lots of carbides present are more agressive than the lower alloy high carbon steels when sharpened at high grits. However if you use a really coarse grit the opposite tends to happen and the high carbon ones are much easier to maintain as they respond better to steeling. I am looking forward to seeing how the CPM steels behave in this regard.

-Cliff
 
Cliff, can D2 be sharpened with a finer grit and act like a course edge? If so would it be more durable than the 5160 exsample you gave?
 
D2 will act coarser than the low alloy steels when the grits are high, but when the grits are low the low alloy steels seem to take a more uniform edge. It would be interesting to match the cutting performances up. For example run a series of tests with D2 sharpened at x-coarse, coarse, fine, x-fine. And then with 5160 and see which gave the maximum slicing performance and durability.

MPS has mentioned in the BUCK forum (in the thread linked to in the first post), that this is exactly the kind of test he will be running soon on a variety of folding hunters. I don't know what the steel types are but it will be interesting regardless. I would actually buy a mag if that kind of info was in it.

-Cliff


[This message has been edited by Cliff Stamp (edited 03 April 1999).]
 
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