Does coarse scratch pattern orientation affect slicing ability?

bpeezer

bpeezer

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Jan 27, 2013
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When cutting with a slicing motion from heel to tip, will the direction of the scratch pattern make a difference in how the blade cuts? Assuming the scratch pattern continues out to the edge consistently and forms micro teeth, will these teeth then be angled along the same lines as the scratches? And if so, does it matter? I'm basically wondering if changing the scratch pattern can be like changing between a push saw and a pull saw. Any insight about scratches perpendicular to the edge would be welcome too :)

Here's a quick sketch of the pattern orientations I'm talking about, let me know if I need to clarify the question further.

Scratch_Patterns.jpg
 
i've found this important on my kitchen knives, even when finishing at high grit. maybe its just me but that's my feeling ...
 
bpeezer said:
When cutting with a slicing motion from heel to tip, will the direction of the scratch pattern make a difference in how the blade cuts? Assuming the scratch pattern continues out to the edge consistently and forms micro teeth, will these teeth then be angled along the same lines as the scratches? And if so, does it matter? I'm basically wondering if changing the scratch pattern can be like changing between a push saw and a pull saw. Any insight about scratches perpendicular to the edge would be welcome too :)

Here's a quick sketch of the pattern orientations I'm talking about, let me know if I need to clarify the question further.

Scratch_Patterns.jpg
Click to expand...

It absolutely makes a difference, and in much the manner you speculate. If you rake the grind path back into the cut it will make a more aggressive draw cut, and a little finer on the push. Perpendicular splits the difference. As the grind path approaches parallel the edge will loose a fair amount of draw efficiency, and the push cut will improve (all else being equal). I do all mine at about a 45 degree rake into a draw and find that is a very happy medium - is also a good angle for maximum angle stability on the abrasive surface (for me). Sometimes when working a coarse stone and in a hurry, I'll use a more shallow rake to get a bit more refinement from it. The effect is noticeable.
 
pwet said:
i've found this important on my kitchen knives, even when finishing at high grit. maybe its just me but that's my feeling ...
Click to expand...

Not just you; I've noticed it even makes a difference in stropping with compound, on a relatively high-grit, polished finish (2000+). When the finish is basically a mirror (to the naked eye), I sometimes alter the rake angle on strops, and can feel small but significant changes in how the edge cuts through phonebook paper. Makes a difference in how fast or how easily the apex 'bites' into the material on the first contact, and how aggressively a 'polished' edge zips through it.


David
 
I'll add one more thought to this - the scratch pattern from circular grinding also seems to have no bias - to me it cuts well, but somewhat erratically. A hodgepodge of characteristics going by with each cut depending where on the edge you are. Actually very good for a utility edge, but I have a tough time deburring without switching to a leading pass. On the other hand, it doesn't seem to matter much as the burr is likewise chopped up and only appears here and there - not enough to compromise cutting quality for general usage.
 
EpicHam said:
snip
Click to expand...

I was referring specifically to angle of scratches in relation to the cut, so the scratches will all be nice and uniform. For instance, take the edge from your first picture. I was questioning if that same edge would cut the same when slicing from either direction.
 
Thanks everyone, now I know I'm not going crazy! Martin, after watching videos of you sharpening on the washboard I changed the way I orient my blade when stropping. I thought I noticed a slight increase in the bite of my edges when slicing, but I wasn't sure if I understood it properly. Now I'm excited to experiment more with this :)
 
bpeezer said:
Thanks everyone, now I know I'm not going crazy! Martin, after watching videos of you sharpening on the washboard I changed the way I orient my blade when stropping. I thought I noticed a slight increase in the bite of my edges when slicing, but I wasn't sure if I understood it properly. Now I'm excited to experiment more with this :)
Click to expand...

Interesting this should come up and you mention it. I'm currently (as in right now at my desk) penning a few pages to be added to the WB manual, one of them deals specifically with this aspect. Is true to some extent on all grinding media, but on the Washboard takes on another dimension as the path the edge takes across the "teeth" will make a noticeable change in edge finish, even with the same rake angle/scratch pattern orientation to cutting edge. You can actually see a change in the scratch pattern even with the same compound, steel, pressure, rake angle etc. Some of this just has to be tinkered with as its too difficult (for me) to verbalize all the variables, but can be figured out quickly with just a bit of noodling and observation. Basically, you can tell just by the change in felt feedback at different angles across the board - as it increases, micro"bite" increases - as it decreases, the edge will exhibit more refinement - this is independent of but relative to the orientation of the scratch pattern - - Hope this makes sense...

In all fairness to myself, I do give the "best practices" in the current manual and in the illustrations show the preferred default rake angle and path across the board, but is easy to overlook as its a single teeny tiny picture upper right on page 4 about the size of a thumbnail :) - hey I was packing in a lot of stuff....

Martin
 
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I noticed this as well at very high grit. When I strop freehand it's always tip to heel and always results in super sharp edges. I was using 0.5u CBN on nano strops for the Edge Pro doing pull strokes only from heel to tip and slicing was not great. After mixing it up and finishing with tip to heel strokes, the edges are sharper than ever.
 
I slice for a living and I'll choose that last illustration as grind pattern.

Of course I prefer smoother scratch pattern (high grit),
 
uofaengr said:
I noticed this as well at very high grit. When I strop freehand it's always tip to heel and always results in super sharp edges. I was using 0.5u CBN on nano strops for the Edge Pro doing pull strokes only from heel to tip and slicing was not great. After mixing it up and finishing with tip to heel strokes, the edges are sharper than ever.
Click to expand...

well... it depends on how you use it .
If you do a lot of pull cutting ,then the last one.
Push cutting , the middle one.

Generally, you'll want the grain to be in the direction of where the material will flow.
 
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