Photos Coarse edges!

[maximus83]

I'm impressed with how effective a 120 edge can be in real-world cutting tasks. Most of my edges on folders and utility FB's I've been doing right around the 280 - 325 range.

 

[David Martin]

Me too. ^ Perhaps the SiC & Inida will break in some finer. DM

 

[maximus83]

So, I'm interested in running with OP's thread idea, and doing up a few more edges on coarse grits. Two of the regular coarse grit sharpeners around here are David Martin and FortyTwoBlades .

If I take a few beaters, reset bevels and resharpen on a coarse grit, here's a few questions for David and Ben.

• Ben: What is the lowest practical grit at which I can get a real-world, working edge for ordinary knife usage? I have your 60-grit Manticore, think I can get a decent usable edge off of that on say, a folder? Any tips for the sharpening process?
• David: I already know I can get pretty decent working edges at 120 grit, using the Crystolon coarse. What do you see as the practical trade-off between stopping at say 120 grit, versus jumping up to something around 280-300, like the Crystolon fine? In other words, what cutting tasks will typically go better--and WORSE--as a result of stopping at that much lower grit?
• What about the medium-coarse grits, say in the 180-220 range? I have SiC stones in this range. Do these grits offer any significant advantage above say the 120? I know that a fair number of factory edges on production folders and fixed blades are applied with belt grinders in this grit range. There has to be some good reason why this grit range gets used so much?

 

[David Martin]

A good question. For my everyday use knife (a Leatherman) I give it a coarse edge with minimal effort as I'll use it for all types of cutting.
And normally have to sharpen it or strop it twice a month. So, I don't want to remove much steel. I often do this edge on a camp knife too.
Now, for a more specific use, like a kitchen knife I'll take it to around 300 grit. As I like the cut surface look this grit leaves. Try some different
grits on your wife's kitchen knife. She'll tell you which one she likes best. Only you will know the grit. I have seasoned meat cutters that tell me they sharpen their blades on the medium SiC (220 grit). Because they can establish this edge quickly and remember
how they'll maintain it. By using a steel... Which will refine it. So, their thinking has solid footing. When I sharpen for payment I always take it
to 350-400 grit as this edge feels sharp and cuts most items really well. Unless they tell me they use it for some special purpose. DM

 

[maximus83]

Ok here's my first entry: a cheap S&W 602 folder. Reset the bevels and sharpened on Baryonyx Manticore, 60-grit. This took about 10 minutes of work, started heavy strokes, went to increasingly light strokes with edge finally running almost parallel to the length of the stone with my last few strokes. This edge shaves arm hair, and will slice cleanly thru receipt paper, cross-wise. For a 60-grit edge produced that quickly, pretty nice results! My conclusion: you can get a very nice working real-world edge as low as 60-grit.

ETA: Stropped this thing, 10 laps per side on 4 micron CBN. This removed a small burr, now it slices even better on paper cutting tests. This is quite an edge off a 60-grit stone, gotta say I'm impressed with the Manticore, and the steel in this knife which cost like $15 on BladeHq.

 

[FortyTwoBlades]

As you noticed, it's very possible to get quite effective edges off of VERY coarse stones. I really like using the edge I get off of my American Mutt stones for paper- and cardboard-slicing as the hyper-aggressive tooth really engages with minimal effort and holds longer than finer grit edges do. But as with all things, it's a matter of choosing the right toothy/polished balance for the mix of tasks you'll be using the tool for. Arguably, for most general utility knives...a pretty coarse edge is a great choice.

 

[me2]

Do files count? For blades cutting light grasses, weeds, & holly bushes, I use a coarse/fine hand-i-file. They will shave my arm straight off the file.

 

[FortyTwoBlades]

Yup. Though files are a little different in their mechanism of removal than stones are.

 

[David Martin]

me2, I've found a coarse edge works well for cutting stemmy weeds. Like Johnson grass, Sacaton, Beargrass and yucca. DM

 

[miso2]

Do files count? For blades cutting light grasses, weeds, & holly bushes, I use a coarse/fine hand-i-file. They will shave my arm straight off the file.

Can I see pics of the edge?
I am curious.

 

[me2]

I don't have any right now. In another week or 2, I'll be sharpening up my Barong and Panga machetes with a file. I file away from the edge with the coarse, then into the edge VERY lightly to remove the burr.

 

[me2]

My wood blades are honed to higher grits, like 1000/4000 water stones.

 

[FortyTwoBlades]

Coarse edges are advantageous on scythe blades in various mowing conditions, as well. The more tender the vegetation, the more polished you go, but the more fibrous it becomes the more a coarse edge really pulls ahead in a big way. The toothier edge is both able to initiate the cut better because it doesn't slip off the tough stalks, but also lasts longer against the more siliceous medium compared to polished edges, which quickly lose that slicing aggression.

 

[miso2]

Make sense.

One of the most polished (or rather smooth) edges with the edge radius around 5 nm (this one is used and probably not that "sharp" anymore).
It excels in push cutting but doesn't seems to have any slicing aggression and slips on skin.

 

[David Martin]

I guess I don't get what you're meaning.? ^ DM

 

[maximus83]

So the above knife with the 60-grit edge, I tried to 'refine' the edge a bit with a plain leather strop. Just messing around, not a real-world reason to do this. After about 20 light laps per side on the leather strop, this edge would push-cut cleanly about 4" to 6" into a piece of newsprint or computer paper before it hangs. And push-cut a couple inches into receipt paper. And still shaves arm hair, but easier with less friction.

This would be an interesting sharpening progression to recommend to somebody: sharpen on 60-grit SiC stone, then a leather strop. Go.

Probably wouldn't use this for much as an EDU type of edge, a little bit TOO coarse for common tasks, and also, I've no idea how durable this edge would be under consistent use. But a fun project to see what a low-grit edge can do.

 

[FortyTwoBlades]

Good alternative to a serrated blade since it's faster to touch up on-the-job.

 

[David Martin]

I think it would hold up well. Sharpening on the ACE Hardware stone would get close to that. I don't think I'd strop it. I would try using it off the stone.I think a coarse edge would take well to tuning. i.e. stropping or a little back-honing. DM

 

[maximus83]

Good point. I've been avoiding serrations for a long time, but there are times when you still want that degree of slicing aggression, but without having to deal with serrations.

Here's a quick subjective example of how this is useful. I took some 1/4" sisal rope, would hold it in a loop, and try to cut through it in a single strong draw cut with edge facing up. Used the above knife, an Ontario Rat in D2, and a Spyderco Domino in CTS-XHP. The latter 2 have nice, but more polished edges at much higher grits. I have no way to measure in foot-pounds how much force it took, but the cheapo S&W with the sawtooth edge was by far the easiest to make the cut. First couple tries, the Rat couldn't even do it, it slipped off the loop until I used more like a sawing motion. Bad! And dangerous. The Domino cut it without sawing, but with considerable torquing on it by me. But the S&W was just a clean straight draw cut and sliced right thru it on the first try.

 

[maximus83]

Good to know, David (about the durability). What I may do is just continue the 'experiment', try using this super coarse edge as an EDU for a while, see how it holds up and how it performs for ordinary knife tasks. The fact it is so coarse and not very good at push-cutting is borderline irrelevant to me, I do not need to push-cut paper (or anything else, really) in my ordinary usage of folding knives.

Also you're right about not stropping an edge like this. If slicing aggression is the objective, then stropping is just going to water that down. I was honestly just messing around and trying stuff, seeing if I could add more performance capabilities to this edge. But for real world usage, there would be no point of stropping an edge like this other than to just quickly realign it after using it a bit.

I think it would hold up well. Sharpening on the ACE Hardware stone would get close to that. I don't think I'd strop it. I would try using it off the stone.I think a coarse edge would take well to tuning. i.e. stropping or a little back-honing. DM