So, why don't polished edges "bite"?

If your polished edge isnt biting like you want it..... make it a thinner edge.

Take a straight razor and slice some stuff up.... it may not bite like a coarse edge, but it will still cut like the dickens.

Remember that polish is secondary to geometry when it comes to performance of an edge.
 
Sparljo said:
Remember that polish is secondary to geometry when it comes to performance of an edge.
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Well, Yes and No. There are many ways to gauge "performance of an edge".

I would suggest that BOTH geometry and polish have a fairly significant impact on some cuts.
 
unit said:
Well, Yes and No. There are many ways to gauge "performance of an edge".

I would suggest that BOTH geometry and polish have a fairly significant impact on some cuts.
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I can agree with that :)

There are much larger gains in improving geometry then increasing polish in my experience. The process of polishing a bevel improves the geometry by default.... its my thinking that some of the perceived gains are really just chopping the bevel shoulders down.

I guess it doesnt really matter.... what Im saying is - If you have a high polished edge that isnt cutting the way you feel it should, thin it out.
 
To me the coarse vs fine edge is over thought . Whereas just rolling up some sleeves and doing some real world cutting would help some items to surface . How steels respond to grits and abrasive mediums when cutting . DM
 
David Martin said:
HH, "cross use of a specific edge could cause it to dull faster" ? Please explain . DM
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I'm speculating that the repeated use of a polished edge for draw cutting could cause it to dull faster than if it were used predominately for a push cut, or (less likely but I'll put it out there) that a coarse edge could dull faster if used repeatedly for push cutting. This I haven't seen - the coarse edge simply isn't as efficient at push cutting but I haven't noticed "premature" wear from using it to push cut. What I have noticed is that my polished edges don't hold up to my normal usage and I do considerably more draw cutting with my EDU knives. Just trying to reconcile the long life I get from my choppers with fairly refined edges, compared to the shorter lifespan from the same edge in a pocket-sized knife.
HH

Edit: Two possibilities I'm entertaining - cutting style and edge bevel. While my choppers do sport refined edges, they do so at bevels approx 40-45 degrees. This alone could account for my results...
 
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i think that's his idea

HeavyHanded said:
a coarse edge could dull faster if used repeatedly for push cutting. This I haven't seen - the coarse edge simply isn't as efficient at push cutting but I haven't noticed "premature" wear from using it to push cut.
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this i can imagine very well. edge less efficient means more force needed to do the cut, more force means more deformation in my books.

still don't get the bite thing. except if what you call bite is what i call "resistance" when slicing. that's why what i consider a slicing edge is 3 to 5k JIS for food prep anything coarser i don't even consider.
 
pwet said:
i think that's his idea



this i can imagine very well. edge less efficient means more force needed to do the cut, more force means more deformation in my books.

still don't get the bite thing. except if what you call bite is what i call "resistance" when slicing. that's why what i consider a slicing edge is 3 to 5k JIS for food prep anything coarser i don't even consider.
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It's kind of hard to describe the bite, but if you ran your fingernail down the edge of a knife, this is what I've observed...

750-1000 grit feels almost "sticky" and before I know it has cut deeply into my fingernail and just doesn't move that freely

1000 grit and some heavy stropping on CrO ( I don't have a higher grit benchstone yet ) and the fingernail can slide up and down as if it were glass and it won't sink in like the other edge did unless I put a bit of pressure on it
 
KennyB said:
It's kind of hard to describe the bite, but if you ran your fingernail down the edge of a knife, this is what I've observed...

750-1000 grit feels almost "sticky" and before I know it has cut deeply into my fingernail and just doesn't move that freely

1000 grit and some heavy stropping on CrO ( I don't have a higher grit benchstone yet ) and the fingernail can slide up and down as if it were glass and it won't sink in like the other edge did unless I put a bit of pressure on it
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Unit started a thread a few days back that offers some member's thoughts on the subject. Don't know if you caught it when it was fresh.

http://www.bladeforums.com/forums/showthread.php?t=824150

Looking at it from the other side of the equation "why do coarse edges have bite?" might give you a little more insight (assuming you're still looking for any).

One issue is that with 1000grit the edge might be a little to far across to benefit from a lot of stropping. I'd almost recommend using black emery for anything under 1500-2000. Stropping by hand, you'll just wipe off the grind pattern and be left with a slightly more broad polished edge than would make for good cutting. I stand behind my earlier assessment though - polishing off the grind pattern leaves the edge better suited for push cuts but reduces its ability to make draw cuts. No texture, less friction, less benefit from lengthwise edge movement.

HH

HH
 
KennyB said:
It's kind of hard to describe the bite, but if you ran your fingernail down the edge of a knife, this is what I've observed...

750-1000 grit feels almost "sticky" and before I know it has cut deeply into my fingernail and just doesn't move that freely

1000 grit and some heavy stropping on CrO ( I don't have a higher grit benchstone yet ) and the fingernail can slide up and down as if it were glass and it won't sink in like the other edge did unless I put a bit of pressure on it
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so allright, i think i got your point now. what you call bite i call resistance.

your analogy pretty much sticks to what have been said about how both type of edges should behave doesn't it ? read what's bolded. you say that the coarse edge grabs and cuts when slicing, and the polished one needs pressure (aka push cut)

that's how i see this.

and once again when slicing meat polishing an edge to 5K is all gain to me. i can cut the portion with less force, less horizontal translation, thus less blade lenght needed to cut the same piece of meat in one clean stroke. one stroke means cleaner job as opposed to going back and forth on the meat in my books. that's how i've been trained at least.
 
pwet said:
so allright, i think i got your point now. what you call bite i call resistance.

your analogy pretty much sticks to what have been said about how both type of edges should behave doesn't it ? read what's bolded. you say that the coarse edge grabs and cuts when slicing, and the polished one needs pressure (aka push cut)

that's how i see this.

and once again when slicing meat polishing an edge to 5K is all gain to me. i can cut the portion with less force, less horizontal translation, thus less blade lenght needed to cut the same piece of meat in one clean stroke. one stroke means cleaner job as opposed to going back and forth on the meat in my books. that's how i've been trained at least.
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Well, I think it comes back to what I found earlier in that I've got a particular cutting technique I've grown use to, and to me applying lots of downward pressure feels awkward, and I can't control the cut as well. I figure I'm just use to making slicing motions with coarser edges.

I don't really see it as making a lot of gratuitous saw like motions though. More like a hybrid of a push-cut and a slice in that I try to move the blade laterally through the material at a higher pace as I'm drawing the edge... Hard to describe as one fluid motion, seems like there's more to it than there really is.

I figure my push-cutting experiences might feel a little better with a polish better than 1000 grit + CrO, because as HH pointed out it's a pretty big leap ( think knifenut once told me it was like jumping from 1000 to 50000 grit), so that could have a lot to do with this too. I'm probably polishing just enough to remove the attributes and characteristics of a coarse edge when slicing, but not really getting it to the point where it can take advantage of the refinement when push-cutting.

Anyway, that's just my guess for now. I keep putting it on my list to buy a polishing stone but haven't got around to it since they're kinda spendy and I always find something else to buy first.
 
Interesting discussion.

I wonder where my edges fall in the continum of polish vs. Course?

I strop my edges with a pretty course buffing compound. I use green #6 polishing compound from the hardware store. It is, I believe, cromium oxide, but pretty course to my eye. I can still see the scratch pattern witth the naked eye with good light.

It will push cut paper just fine, but seems to also draw cut fine as well.

Will jump hair off the arm, but at the angles I use, it is borderline to treetop. The edges on most of my users is probably 40+ inclusive, maybe as high as 50 inclusive.

Pretty durable edges under hard use.
 
Interesting discussion.

I wonder where my edges fall in the continum of polish vs. Course?

I strop my edges with a pretty course buffing compound. I use green #6 polishing compound from the hardware store. It is, I believe, cromium oxide, but pretty course to my eye. I can still see the scratch pattern witth the naked eye with good light.

It will push cut paper just fine, but seems to also draw cut fine as well.

Will jump hair off the arm, but at the angles I use, it is borderline to treetop. The edges on most of my users is probably 40+ inclusive, maybe as high as 50 inclusive.

Pretty durable edges under hard use.
 
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