Damn. Another 'polished vs toothy' thread...

One thing to watch out for is the difference between a coarse edge at a given grit value and an edge that has been crafted from a coarse stone to behave as a more refined one. If an edge is cutting like a more refined one, then it is no longer cutting like a more coarse one - sounds obvious but there are implications.

Another consideration is the extreme variation in line viewed from the side, a by-product of the relatively low concentration of abrasives and high unit pressure make it difficult to produce intersections at the low points that are 100% burr free (this speaking to the macro-coarse edges) - it is difficult or impossible to work the same point from opposing sides, only the high spots primarily experience this (imagine corrugated roofing with an edge cut into it, now flip). This is relative - an abrasive field with high friability/refresh rate and some vehicle (lube or binder) will behave differently from one that lacks one or both of these traits.

On the plus side, even if they do have small burring they will still cut very well, and protected by the higher points to either side tend to have good longevity as well. Particularly excelling in relatively shallow, drawing cuts on light to medium density materials or ones that aren't held together tightly, allowing less pressure to be used.

As the density and hardness of a target material increase, the variation in line that lets it cut so aggressively becomes a hindrance as it increases friction and drag. This is where a refined edge comes in and parts the material with less pressure - all things being equal.

Not to overthink it, but steel as it pertains to a cutting edge is basically a kick-butt micro-sculpting medium.
 
I don't think the culprit is the edge or the sharpness of his knife. The problem lies in the environment in which the OP is operating. He's cutting a steak on a ceramic substrate. Sure it's enough to dull the blade. If you think about it, the restaurant serves on a ceramic plate. Don't care what steel you have, that ceramic plate is harder. He could have a knife made and sharpened by God himself, and it'll have the same outcome. It's like how those sharpening videos run the edge of their knives on a ceramic rod purposely to dull the blade for demonstration. Same reason you never use a glass, marble, granite, or solid surface cutting board in the kitchen. You'll dull each and every knife you have faster than,....faster than,.... Well you get my drift.

I use my edc all the time at steakhouses because their house steak knives suckkkk! Been to 5-star steak houses that offered KAI steak knives and they suckkkked too. Think of all the mindless patrons that grind the knives into the plate. No way they have a blade smith on hand to maintain the edges. Use your Edc. Be aware of where the edge is and ease up on cutting as you get near the plate...and stop just when you feel the edge touch the plate. Key is not to continue back and forth grinding the edge into the ceramic plate. Nothing like the texture of a fine steak sliced by a laser sharp knife instead of a torn up piece done up with a crappy house steak knife.

Edit: just reread your original post- acknowledge you didn't grind into the plate. As the others mention, the blade still may have hit. Just my guess. Maybe just rounded the edge. Just strop that puppy and bobs your uncle.
 
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lonestar1979 said:
edges off coarse dmt are amazing,easily shave hair too.
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Yes. Usually I'll put in a final micro-bevel with a medium stone, but sometimes I finish up with a coarse diamond hone...

When fully re-profiling, I'll start with extra-coarse diamond, and even that alone can get somewhat sharp.

As for the OP issue: Sebenzas are not known for their edge-holding. Maybe a wire edge was in there...

The biggest problem with any sharpening is the wire edge: Wire edges are probably the main reason coarse knife edges have such a bad reputation...: It is actually very hard to create a true coarse apex on an edge without putting some wire edge in there: Taking out the wire edge polishes off the coarse apex to a medium finish anyway, which is why the problem is almost more like keeping the coarseness in than the other way around...

This is probably why people think they get better performance out of polished edges: Polishing takes the wire edge out, so they compare the performance of a wire-edge free polished edge to a unseen wire-edged coarse edge, and think that's a fair comparison...

That being said, probably 90% of all the cutting done in history, and most of the major battles fought, was all done with wire edges...

Mirror polished edges also give a good illusion of sharpness when the edge angle is 15 per side or over. It is a crutch to the essential dullness of the wide open 30 degrees (or more) inclusive edge... With a non-rounded off mirror edge, even a 20 degrees per side edge will seem aggressive on some materials, especially the shaving or paper test...

If people did not so obsessively polish their edges, and tested on less favourable mediums (instead of pushing down on laid down manila rope, like one guy touting polished edges did), they would know how actually dull their knives are...: A test I like to do goes as follow: Take a cheap paperback novel, laid flat open, and just barely curl up a page corner, no crease bending, just holding it up so that it would go back to perfect flat without holding it: The edge should approach perpendicular to the paper edge, looking down from above: Now here is the difficult part: Cut the paper with only the last quarter inch of the point...

Of course thin kitchen knives, maybe even thin point folders, will do great at this, but most seriously rigid outdoor knives will just push the paper down...: The geometry of the tip is often just too awful to even bite the paper...

Highly polished edges with an open 15-20 per side edge angle will dull quicker: Polished edges dull faster, and this combines with the more open angle being much more dependent on that apex polish than a more closed angle. Combine that with a Sebenza, with often less edge holding than Chinese mystery steel (which can still mean quite acceptable edge-holding), and the experience of the OP is not so surprising.

Gaston
 
HeavyHanded said:
One thing to watch out for is the difference between a coarse edge at a given grit value and an edge that has been crafted from a coarse stone to behave as a more refined one. If an edge is cutting like a more refined one, then it is no longer cutting like a more coarse one - sounds obvious but there are implications.

Another consideration is the extreme variation in line viewed from the side, a by-product of the relatively low concentration of abrasives and high unit pressure make it difficult to produce intersections at the low points that are 100% burr free (this speaking to the macro-coarse edges) - it is difficult or impossible to work the same point from opposing sides, only the high spots primarily experience this (imagine corrugated roofing with an edge cut into it, now flip). This is relative - an abrasive field with high friability/refresh rate and some vehicle (lube or binder) will behave differently from one that lacks one or both of these traits.

On the plus side, even if they do have small burring they will still cut very well, and protected by the higher points to either side tend to have good longevity as well. Particularly excelling in relatively shallow, drawing cuts on light to medium density materials or ones that aren't held together tightly, allowing less pressure to be used.

As the density and hardness of a target material increase, the variation in line that lets it cut so aggressively becomes a hindrance as it increases friction and drag. This is where a refined edge comes in and parts the material with less pressure - all things being equal.

Not to overthink it, but steel as it pertains to a cutting edge is basically a kick-butt micro-sculpting medium.
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What happens if we put a coarse finish on one side of the bevel and debur with a fine stone on the other? Best of both worlds?

In my experience a coarse edge of say 280 grit lansky can push cut remarkable well if carefully deburred and finished with light strokes.
 
MichaelMyers said:
What happens if we put a coarse finish on one side of the bevel and debur with a fine stone on the other? Best of both worlds?

In my experience a coarse edge of say 280 grit lansky can push cut remarkable well if carefully deburred and finished with light strokes.
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This is actually how some of the older scalpels used to be done, but in that case I believe it was more for manufacturing ease. In my experience it worked out as a split difference more or less, so 320 on one side and 1200 on the other it cut more or less like an 800 grit finish. This is something you could experiment on a bit more, I didn't do a ton of work with this strategy. By hand I recall having issues cleanly deburring.

For myself if I want a toothy edge I don't much try to incorporate finer cutting into it as well. Meaning I'm not going to work one stone with extra care when I can use two, or one and a steeling/burnishing operation and get the job done faster and more reliably in my hands - if that's what I'm after. If I need a rough edge, I leave it rough - maybe shaves a few armhairs and can slice newsprint. Anything I do to push it into more of a mixed use edge will reduce longevity on hard work. Now if one is in a situation where you have to make do with one stone and you just want the most refined edge possible with the gear at hand is a different story.
 
I used to polish edges before,and work through variety of stones,waterstones,strops,etc and found doing that mostly useless aside from cosmetic side.Now I just use coarse finish on dmt or Norton silicon carbide coarse-medium and strop on back of my palm or piece of leather.These edges shave hair easily but cut everything much better than really polished edges.Working with wood is another story,then polished edges perform better.Depends what you prefer,push cutting or sawing action cutting!For some people its a hobby too:).Ceramics are used for sharpening knives too(use back of plate sometimes to touch up my knives), and plate will easily dull any knife and any edge.
 
ursamajor said:
I guess the truth is funny? Must explain why for precise cutting tasks, surgeons use ultra fine obsidian scalpels...because they are inferior slicers to ragged edges?

I guess I'm going to hear next how 2 cycle engines, can run for more operating hours that diesel engines.

I will concede that the internet is funny.
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Comparing surgery on a living human being to cutting a steak is a bit silly don't ya think?
 
ursamajor said:
It's all muscle...
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Of all the surgical procedures being done very very few are done with obsidian or diamond blades, and just as often for reasons of site purity rather than for added precision. Where used for precision is when dealing with cosmetics for a slightly finer initial scarring - skin, not muscle - and this is a rarity.

Anecdotally a (somewhat) rougher edge makes a wound that heals faster. As fsatsil says, not really a comparison in the current conversation.
 
Obsidian scalpels are (quite rarely) used because obsidian is simply capable of achieving a much higher level of sharpness than steel. Polished and toothy edges don't even enter into the equation when discussing it.
 
I'm not sure if the obsidian scalpel is even applicable to the OP, but they aren't used more often likely because they provide no tangible benefit for most surgical procedures and come with notable drawbacks.

They are extremely fragile and more expensive. Having a piece of your scalpel come off in a surgical incision would not be good, any more than having a piece come off in your sirloin.
 
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