Performance Differences Between Coarse and Fine Edge?

[RedLynx]

Hi guys,

Just got a couple knives back from Jason B. that I could not get sharp (referenced in a couple of my other threads so I won't bother here). He finished one with 400 grit and one with 5000 grit so I could get a feel for differences in a coarse vs. fine edge. I'm sure I'll use both a fair amount in due time, but since I just got them back and will only be carrying one for awhile I wanted to ask here: (could have emailed him but he seems to be a pretty busy guy and I don't want to bug him too much)

What are the general performances differences here? I assume one is better than the other for certain things and vice versa?

The finest grit I have is 1200 on one side of my DMT stone, so I've never used anything finished close to 5000.

Thanks for your input guys.

 

[BluntCut MetalWorks]

Here is a short answer:

Coarse edge good for saw/draw/rip/tear cutting activities.

Find edge good for push/chop/whittle cutting activities. Generally best suited for fine grain & sub micron carbide size steels.

 

[HeavyHanded]

What he said ^

basically the coarse edge has more irregularities that catch and separate materials when drawn across the surface as it cuts. Performance increase can be quite impressive compared to more refined edges depending on application. This increase in draw cutting generally leads to a loss of performance when chopping or pressing into a material, the irregularities lead to greater resistance.

As the level of refinement goes up the edge has less resistance when chopping/carving and much better shaving characteristics.


Also important to note that all sharp edges are sub-micron, but the coarse edge is sub-micron in spots along the edge - more refined edges have greater percentage of edge sub-micron.

For everyday use, a somewhat toothier edge tends to work a little better on many synthetic materials and in general will have longer life.

The 5K finish is likely in Japanese scale, so closer to a 1500 grit in Western terms, not too much more refined than the DMT, at least on paper. Diamonds tend to make deeper scratches per compared to waterstones, so that 5K liable to cut very refined compared to the 1200 DMT.

 

[David Martin]

For everyday general use cutting, I'll sharpen mine more coarse. More around 300 grit or less. This greatly increases edge retention well beyond the fine grit edge. This is capable of shaving arm hair, cutting rope or peeling an apple, etc.. Plus an added benefit is when this edge becomes dull I can bring it's edge back by coarse stropping without much refinement. I'm not OCD about sharpening. DM

 

[Rich S]

For general use I tend to go with a 600 grit and stropping. For a fine edge
I go to 1500 with stropping. Both have their uses as mentioned above.
Rich

 

[Jason B.]

The edges on the knives were both applied by a Japanese waterstones. The coarse, a Naniwa Pro 400 (new chosera) with a light stropping on denim to clean up any remaining burr. The fine, a Shapton Pro 5000, no stropping required. The 5k yields a edge somewhat like a natural stone so it's very toothy compared to other 5k stones.

The knives were both the same so it makes for a good end user test. They were CRKT folders with 8cr steel so, low alloy stainless. Personally, I like a more refined edge on such steels but it's always good to get some feedback from customers.

 

[RedLynx]

What he said ^

basically the coarse edge has more irregularities that catch and separate materials when drawn across the surface as it cuts. Performance increase can be quite impressive compared to more refined edges depending on application. This increase in draw cutting generally leads to a loss of performance when chopping or pressing into a material, the irregularities lead to greater resistance.

As the level of refinement goes up the edge has less resistance when chopping/carving and much better shaving characteristics.


Also important to note that all sharp edges are sub-micron, but the coarse edge is sub-micron in spots along the edge - more refined edges have greater percentage of edge sub-micron.

For everyday use, a somewhat toothier edge tends to work a little better on many synthetic materials and in general will have longer life.

The 5K finish is likely in Japanese scale, so closer to a 1500 grit in Western terms, not too much more refined than the DMT, at least on paper. Diamonds tend to make deeper scratches per compared to waterstones, so that 5K liable to cut very refined compared to the 1200 DMT.

Ah, okay, didn't know that about the 5K, thank you!

So in general, coarse edge great for everyday outdoor/woods activities, fine edge great for opening boxes, plastic, packaging, etc (just listing some things I do with knives.)

 

[chiral.grolim]

So in general, coarse edge great for everyday outdoor/woods activities, fine edge great for opening boxes, plastic, packaging, etc (just listing some things I do with knives.)

I would say just the opposite:

Coarse edge good for saw/draw/rip/tear cutting activities.

Find edge good for push/chop/whittle cutting activities. Generally best suited for fine grain & sub micron carbide size steels.

Outdoor/wood activities generally prefer a finer edge for push-cutting. Opening packages usually prefers a coarse edge for draw-cutting.

 

[HeavyHanded]

So in general, coarse edge great for everyday outdoor/woods activities, fine edge great for opening boxes, plastic, packaging, etc (just listing some things I do with knives.)

I would say just the opposite:
Outdoor/wood activities generally prefer a finer edge for push-cutting. Opening packages usually prefers a coarse edge for draw-cutting.

Yes ^

Fine edges for woodworking, less refined edges for EDU. Steel type plays a role as well, but in general...

 

[Obsessed with Edges]

Here is a short answer:

Coarse edge good for saw/draw/rip/tear cutting activities.

Find edge good for push/chop/whittle cutting activities. Generally best suited for fine grain & sub micron carbide size steels.

Ditto. :thumbup:

The edges on the knives were both applied by a Japanese waterstones. The coarse, a Naniwa Pro 400 (new chosera) with a light stropping on denim to clean up any remaining burr. The fine, a Shapton Pro 5000, no stropping required. The 5k yields a edge somewhat like a natural stone so it's very toothy compared to other 5k stones.

The knives were both the same so it makes for a good end user test. They were CRKT folders with 8cr steel so, low alloy stainless. Personally, I like a more refined edge on such steels but it's always good to get some feedback from customers.

This is my take on 8Cr as well. I've got several knives in 8Cr from A.G. Russell, and I like the edges they'll take at high-satin or near-mirror finish (by naked eye, at grits above 600-1000 or higher).

I would say just the opposite:



Outdoor/wood activities generally prefer a finer edge for push-cutting. Opening packages usually prefers a coarse edge for draw-cutting.

Regarding opening packages and such, so long as the apex is crisp, I've liked anything from 320 and up (to 2000+); the finer-grained the steel is, the better it'll do at a higher finish (finer-grained steel usually does well across the spectrum, for that matter). All of the knives I've used for these tasks are thin convexes at essentially mirror polish, in 1095 (Schrade), CV (Case) and 420HC (Case & Buck), as well as 440A/C (Kershaw, Buck) and 12c27Mod & XC90 (Opinel). Coarser-grained stainless, such as found on inexpensive & older kitchen knives, seems to do better with edges at 320 or less.


David

 

[RedLynx]

This is my take on 8Cr as well. I've got several knives in 8Cr from A.G. Russell, and I like the edges they'll take at high-satin or near-mirror finish (by naked eye, at grits above 600-1000 or higher).
David

Thanks David,

Both knives in question above were actually 8cr CRKT knives.

 

[RedLynx]

The edges on the knives were both applied by a Japanese waterstones. The coarse, a Naniwa Pro 400 (new chosera) with a light stropping on denim to clean up any remaining burr. The fine, a Shapton Pro 5000, no stropping required. The 5k yields a edge somewhat like a natural stone so it's very toothy compared to other 5k stones.

The knives were both the same so it makes for a good end user test. They were CRKT folders with 8cr steel so, low alloy stainless. Personally, I like a more refined edge on such steels but it's always good to get some feedback from customers.

Thanks Jason,

Yes I expect it will be quite insightful for me, since I only use one sharpening medium, the two-sided DMT, and I am not super familiar with much of anything else. (I tried to tell which knife had which edge by using my thumb, but I couldn't really). One knife did seem to make straight push cuts a bit smoother but I haven't have a chance to use both side by side yet.

 

[Jason B.]

The really shiny edge is the 5k one

 

[RedLynx]

The really shiny edge is the 5k one

Thanks!

 

[calc]

Fine edge for push cutting, e.g., wood carving and vegetable chopping. I prefer low alloy steel for these applications.

Course edge for draw cutting, e.g., package opening and rope slicing. I prefer high carbide steel for these applications.

 

[Ankerson]

For everyday general use cutting, I'll sharpen mine more coarse. More around 300 grit or less. This greatly increases edge retention well beyond the fine grit edge. This is capable of shaving arm hair, cutting rope or peeling an apple, etc.. Plus an added benefit is when this edge becomes dull I can bring it's edge back by coarse stropping without much refinement. I'm not OCD about sharpening. DM

I generally use 320-400 grit across the board and it works fine for me for everything from kitchen use to wood. :thumbup:

 

[RedLynx]

I generally use 320-400 grit across the board and it works fine for me for everything from kitchen use to wood. :thumbup:

I'll have to try that. Actually I may need to get a coarser stone, I think I have 800 on one side and 1200 on the other. I've always finished with 1200, but perhaps I'd get improved results if I just went coarser.

Although don't you essentially reprofile the blade every time? I heard I should only go quite coarse if the knife is really dull and in need of reprofiling.

 

[Ankerson]

I'll have to try that. Actually I may need to get a coarser stone, I think I have 800 on one side and 1200 on the other. I've always finished with 1200, but perhaps I'd get improved results if I just went coarser.

Although don't you essentially reprofile the blade every time? I heard I should only go quite coarse if the knife is really dull and in need of reprofiling.

No, I do light touch ups using ceramics or a SIC loaded strop.

If you need to remove a lot steel then the coarser the better and work up to and finish with 320-400.

I usually use 120/320/400.

 

[RedLynx]

No, I do light touch ups using ceramics or a SIC loaded strop.

If you need to remove a lot steel then the coarser the better and work up to and finish with 320-400.

I usually use 120/320/400.

So you just make a few passes on the ceramics, if I understand you correctly?

I must confess I've never stropped, what is a SIC loaded strop?

 

[Ankerson]

So you just make a few passes on the ceramics, if I understand you correctly?

I must confess I've never stropped, what is a SIC loaded strop?

Yes, just a few passes and that's it.

Silicon Carbide loaded leather strop.