Sharpening trade off?

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sinsanity

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Dec 17, 2010
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sorry if this is a stupid question but....

when sharpening as you progress through the grit sizes from coarser to finer you have to have a trade off from less bite in slicing to better push cutting?

I noticed this when I sharpened my kershaw leek to extra fine on my dmt stones and it didn't "bite" (grab?) the paper as well when I tested it for sharpness but it push cut well. There would be times when it wouldn't slice through and the paper would squeak.

Is this normal or am I doing something wrong in my sharpening? :confused:
 
Sounds reasonable to me. Some folks have been known to give the edge a few LIGHT passes on a medium grit stone to add "micro serrations" to a finely finished edge.
 
Barring any considerations of stropping and how different steel types respond to different grinding media, there is a direct correlation between coarse and fine edges, and draw and push cutting. If you were to take any knife and test it against a variety of materials as you went through a progression from 80 grit up to 10,000 or beyond, you'd see the change in cutting characteristics quite clearly. Every material/application has an edge preparation that is ideal, with all other preparations being a compromise. The trick is to find out what works best for what you cut the most and how you do it. This will also probably give you the best longevity.

HH
 
You might take a magnified look (10x or better) at the full length of your cutting edge. More often than not, when I've noticed the edge is skipping/slipping during a slice cut, it usually indicated a less-than-complete bevel on some portion of the cutting edge. Often, it's back near the ricasso, where even factory grinds sometimes aren't quite finished all the way to the edge. When it still has some 'teeth' on it, an imperfect bevel will still slice reasonably well. As it becomes more polished and the teeth are removed, cutting will depend more on the true sharpness & shape of the edge, to still be effective. A push cut is obviously going to be done with only a very short portion of the edge (usually somewhere near the central portion), but a slice cut relies on most or all of the edge. When the edge is completely apexed (truly sharp) along the full length, it shouldn't matter if it's polished or not, especially when cutting paper edgewise. In my experience, when the edge is completely finished & polished along the full length, slice cutting paper is a 'whisper quiet' breeze, and the push-cutting will take care of itself.
 
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sinsanity said:
sorry if this is a stupid question but....

when sharpening as you progress through the grit sizes from coarser to finer you have to have a trade off from less bite in slicing to better push cutting?

I noticed this when I sharpened my kershaw leek to extra fine on my dmt stones and it didn't "bite" (grab?) the paper as well when I tested it for sharpness but it push cut well. There would be times when it wouldn't slice through and the paper would squeak.

Is this normal or am I doing something wrong in my sharpening? :confused:
Click to expand...

it's not in your head, using a coarser grit will make the edge "grab" more. it has to do with the micro serrations created by the sharpening stone. the finer the stone, the smaller ("finer") the micro serrations are. from my experience, certain steels work well with a toothy edge, while others work better with a finer edge. also, the type of material you cut, the grit you finish with and the steel/heat treat will effect how the edge will perform. before i sharpen a knife, i take into consideration all of those factors plus edge angle to get the most performance out of a specific blade. i made a thread a few days ago showing s30v under my microscope with edges made by different grits. here is the link:
http://www.bladeforums.com/forums/showthread.php?p=9224883#post9224883. the low power shots are taken at about 40x, the high powered shots are taken at about 375x.
 
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