Scratch pattern when sharpening

[samuraistuart]

I was hoping you guys could "edumicate" me on scratch patterns when sharpening knives. My whole life I never gave it a thought, to change directions when sharpening. I used to use simple straight across the stone motions, like back and forth for heavy material removal. Once the edge was established I would go to the usual sweeping motion starting at the ricasso area, sweeping down and finishing off at the tip area.

I came across a thread where it was mentioned to change that sweep and go the other direction, like start with the tip and then end at ricasso. I hope that makes sense. Basically, whatever scratch pattern you get when sharpening, make the scratches go the other way as well.

I think I remember a term called "cut bias" or something like that. If all the sharpening was done in one direction, then the micro scratches along the edge will cause a "bias" when slice cutting one way or the other. The idea being to minimize this "bias" by alternating your stroke directions.

What do you guys think about that? Is it noticeable in a fine polished edge, or is this more for the "toothy" edges? Do you do this very thing, alternating directions because of the scratch pattern?

Just curious is all. Just came across this concept and was hoping to get your input. Thanks so much!

 

[REK Knives]

grind direction plays a huge role in how well your edge will cut, for sure!!

one thing that wasn't clear about the way you do it... do you do that motion edge leading or edge trailing?

I finish all of the knives that I sharpen edge leading, heel to tip passes. the reason for this is that most people use their knife in a pulling or drawing type fashion. If you angle the grind in this manner, the 'micro teeth" that are formed by the last stone used will be "angled" into the cut, thereby maximizing the cutting ability.

The exception are some large chef knives that are used with a "down and into" it slicing motion when cutting.

Not sure about high polish finishes but I would think so... when I finish straight razors I do it in the same manner.

 

[Obsessed with Edges]

I've noticed subtle differences in slicing (& sometimes unmistakable differences), when I'm aware of the grind pattern being oriented in different directions. Regarding terminology, if I'm not mistaken, I think member HeavyHanded has referred to the 'rake angle' of the scratches along the bevel, and how cutting changes according to which way those scratches lean (such as forward-leaning, with the upper end of the scratches oriented toward the tip, and lower end of the scratches toward the ricasso).

Since most of my cutting or slicing is usually done with a heel-to-tip draw stroke, I prefer to orient the scratches in a somewhat 'forward-leaning' fashion, as described above. Oriented as such, the 'tips' of the grind pattern at the apex would seem to get better 'bite' in a heel-to-tip draw cut. On the stones, I'd lay the blade somewhat diagonal to the length of the stone, with the tip of the blade pointed to the 'away' corner of the stone, then drawing the blade from heel-to-tip down the length of the stone, with the tip following in the stroke. Maybe perpendicular scratches might be ideal for either heel-to-tip or tip-to-heel slicing, and perhaps also for push-cutting, in which case the blade's spine would be laid perpendicular to the length of the stone, and the stroke would be dead-straight towards the ends of the stone.


David

 

[Moondrop]

Have wondered about this myself, and for a long time now have made a conscious effort to angle the scratches the way the two posters above me have described, for the reasons they explained. I couldn't be sure it made a difference even as I was doing it, but it seemed to make sense to me. LOL

 

[HeavyHanded]

The effect is noticeable on all but the brightest polish finish, and even then maybe...

I generally work at about a 45* rake angle for two reasons - this gives me the best support on the stone to prevent rocking at the start of each push/pull, and I have less angle deviation. If done well, it actually induces a slightly finer cut on the forward pushing action at a given grit, and a more aggressive pull - all other things being equal.

 

[samuraistuart]

Razoredge, I do exactly how you described. Edge leading, heel to tip. Flip. Repeat! And that is what I had in mind as well....the micro teeth would be in the right orientation for a pull slicing cut. Thanks for all the info guys. Just something new I've started to incorporate into my sharpening. I change directions every grit. For example 220 heel to tip, then tip to heel where the scratches will cross the old ones by about 45 degrees or so. Then 600 grit, alternate scratch pattern as well. On up to my final grit, where I still will "cross hatch" the scratch pattern, but finish off on heel to tip edge forward strokes.

I don't care too much for edge trailing strokes even on the final polishing grits. For some reason the knife does not seem as keenly sharp when I do that. It may have some improved cutting performance....I really don't know if it does or not. But I tend to favor edge leading 99% of the time. I don't even strop on leather. I am amazed how sharp I can get a knife at 325 grit. Yesterday I had to do a friend's Kershaw that has 14c28n. Lovely steel, BTW. After resetting the bevel on 120 and refining on 220, the coarse DMT 325 grit had the thing popping hairs off of my arm. And went all the way up to 1800US grit. Insanely sharp! No need for strop at all.

 

[REK Knives]

Razoredge, I do exactly how you described. Edge leading, heel to tip. Flip. Repeat! And that is what I had in mind as well....the micro teeth would be in the right orientation for a pull slicing cut. Thanks for all the info guys. Just something new I've started to incorporate into my sharpening. I change directions every grit. For example 220 heel to tip, then tip to heel where the scratches will cross the old ones by about 45 degrees or so. Then 600 grit, alternate scratch pattern as well. On up to my final grit, where I still will "cross hatch" the scratch pattern, but finish off on heel to tip edge forward strokes.

I don't care too much for edge trailing strokes even on the final polishing grits. For some reason the knife does not seem as keenly sharp when I do that. It may have some improved cutting performance....I really don't know if it does or not. But I tend to favor edge leading 99% of the time. I don't even strop on leather. I am amazed how sharp I can get a knife at 325 grit. Yesterday I had to do a friend's Kershaw that has 14c28n. Lovely steel, BTW. After resetting the bevel on 120 and refining on 220, the coarse DMT 325 grit had the thing popping hairs off of my arm. And went all the way up to 1800US grit. Insanely sharp! No need for strop at all.

in my experience the optimum use of edge leading/trailing is:

1. edge leading for diamond stones
2. edge trailing for waterstones (even when clean, with or without slurry)

 

[ToddS]

...
2. edge trailing for waterstones (even when clean, with or without slurry)

Josh,
Are you doing this to deliberately form a burr?
I do know that a few edge trailing strokes can improve keenness after honing edge leading.

Also, can anyone tell me how to make a "toothy" edge?

 

[REK Knives]

Josh,
Are you doing this to deliberately form a burr?
I do know that a few edge trailing strokes can improve keenness after honing edge leading.

Also, can anyone tell me how to make a "toothy" edge?

No, not to deliberately form a burr... I am doing this based off of two things:

1. it's what Murray Carter advocates and he has a little more experience than me lol
2. Although I only have a 230x usb microscope, when comparing edge leading vs edge trailing w/ waterstones (specifically on my 10k choseras), I notice that edge leading always seems to product micro chipping at at least one point along my blade - which I cannot have on straight razors. I will try to get some photos of this soon.

On the latter point this is after they are freshly lapped and chamferred too, but maybe I could have missed something or gotten some contamination on it. It just seems safer to me to do edge trailing.

Is your experience different?

 

[ToddS]

Josh, is when honing your razor in the Wicked Edge?

My feeling is that the edge-leading "damage" is what prevents a burr from forming. In the few edge-trailing experiments I have done, a burr has formed. I haven't looked at this in any detail, and would not make any generalizations.

There is a 'trick' used in razor honing, to finish with a couple of edge-trailing strokes on the high grit stone (eg 16k or 20k) and this does improve keenness by forming the beginning of a burr.

 

[REK Knives]

Josh, is when honing your razor in the Wicked Edge?

My feeling is that the edge-leading "damage" is what prevents a burr from forming. In the few edge-trailing experiments I have done, a burr has formed. I haven't looked at this in any detail, and would not make any generalizations.

There is a 'trick' used in razor honing, to finish with a couple of edge-trailing strokes on the high grit stone (eg 16k or 20k) and this does improve keenness by forming the beginning of a burr.

Yes I sharpen straight razors on my Wicked Edge.

I would be interested to see a study done on this on an SEM, but you would have to do it at different power levels so you could "zoom out" to see the affect over a broad part of the edge to see if there is any "damage" when edge leading. I am picturing the edge that edge trailing passes leave (which is done alternating strokes, extremely light pressure) to look similar to this, which *should* be fixed up and the very weak metal removed with light stropping, slightly lowered angle:

 

[HeavyHanded]

Josh,
Are you doing this to deliberately form a burr?
I do know that a few edge trailing strokes can improve keenness after honing edge leading.

Also, can anyone tell me how to make a "toothy" edge?

Here is my working theory -

A more coarse abrasive will make the toothier edge, it can then be "refined" a bit with a hard, fine abrasive such as a ceramic rod. It can also be 'steeled' on a smooth steel or glass rod etc. A medium grit finish burnished on a steel or glass makes for a crazy mix of toothy and refined cutting qualities. Some will take an edge up to a high polish and then apply a few passes with a coarser stone to make a toothier microbevel. The goal of these strategies is to keep the irregularities along the edge that catch and separate materials, but reduce the increase in distance across the apex that comes from working with coarser abrasives, allowing the edge to penetrate deeper with less force.

On hard, fixed abrasive surfaces, I do not believe one can readily use a trailing pass to finish with predictable results - a burr will want to form almost immediately, so easier to use a leading pass and apply some post-grinding operation to thin or otherwise unify the apex a bit. Stropping on plain paper over a hard surface with a fair amount of force can acheive a bit of burnishing as well. Does a great job of preserving the underlying irregularities.

Another strategy is possible by backhoning on a hard surface with loose abrasive in a slurry, which reduces the depth the abrassives cut along the bevel face, but seems to increase or preserve the amount of irregularities along the edge. This gives you the thin apex but a high density of irregularities along the edge. Most who work with waterstones and finish with a trailing pass will note the 'catchiness' of the edge compared to finishing with a leading pass. I believe this is largely due to a "micro breakout" effect that somewhat loose abrasives have along the edge when used with a trailing motion on a hard surface. A fairly thick slurry applied to a hardwood board makes the most aggressive example of this sort of edge that I have been able to manage, but the slurry consistency, texture of the board, type of abrasive and other binders all come into play in ways that make it user unfriendly in many respects. Is inexpensive to set up and well worth playing with.

[video=youtube;gfblDsTy-FY]https://www.youtube.com/watch?v=gfblDsTy-FY[/video]

 

[REK Knives]

Here is my working theory -

A more coarse abrasive will make the toothier edge, it can then be "refined" a bit with a hard, fine abrasive such as a ceramic rod. It can also be 'steeled' on a smooth steel or glass rod etc. A medium grit finish burnished on a steel or glass makes for a crazy mix of toothy and refined cutting qualities. Some will take an edge up to a high polish and then apply a few passes with a coarser stone to make a toothier microbevel. The goal of these strategies is to keep the irregularities along the edge that catch and separate materials, but reduce the increase in distance across the apex that comes from working with coarser abrasives, allowing the edge to penetrate deeper with less force.

On hard, fixed abrasive surfaces, I do not believe one can readily use a trailing pass to finish with predictable results - a burr will want to form almost immediately, so easier to use a leading pass and apply some post-grinding operation to thin or otherwise unify the apex a bit. Stropping on plain paper over a hard surface with a fair amount of force can acheive a bit of burnishing as well. Does a great job of preserving the underlying irregularities.

Another strategy is possible by backhoning on a hard surface with loose abrasive in a slurry, which reduces the depth the abrassives cut along the bevel face, but seems to increase or preserve the amount of irregularities along the edge. This gives you the thin apex but a high density of irregularities along the edge. Most who work with waterstones and finish with a trailing pass will note the 'catchiness' of the edge compared to finishing with a leading pass. I believe this is largely due to a "micro breakout" effect that somewhat loose abrasives have along the edge when used with a trailing motion on a hard surface. A fairly thick slurry applied to a hardwood board makes the most aggressive example of this sort of edge that I have been able to manage, but the slurry consistency, texture of the board, type of abrasive and other binders all come into play in ways that make it user unfriendly in many respects. Is inexpensive to set up and well worth playing with.

[video=youtube;gfblDsTy-FY]https://www.youtube.com/watch?v=gfblDsTy-FY[/video]

Great post here HH... On your last example; I do not do edge trailing on waterstones with slurry on them currently. My best results on waterstones have been edge trailing on a clean stone with no slurry until the stone starts to get glazed. Then I add a little more water but do not clean the pores out, then continue "stropping" on that stone until it's dry. Seems to give me the best results so far.

 

[ToddS]

I'm definitely missing something here.
These are a couple of images from a straight razor finished edge-leading on a DMT 325 with water. I don't see teeth, and it's not obvious to me that the direction of the scratches would affect the cutting performance.

 

[BluntCut MetalWorks]

Todd, cool SEM pics! Looking at your angle, I agree with your assessment.

From my view - I see a few things: undulating apex (z-teeth); ridges teeth face; a lot of burnishes - probably from flat-top diamonds. Also razor steels usually quite ductile. If you like to look at something a little harder and more alloy. I can send you a paring 52100 63+rc and a tiny D2 blades.

I'm definitely missing something here.
These are a couple of images from a straight razor finished edge-leading on a DMT 325 with water. I don't see teeth, and it's not obvious to me that the direction of the scratches would affect the cutting performance.

 

[HeavyHanded]

Great post here HH... On your last example; I do not do edge trailing on waterstones with slurry on them currently. My best results on waterstones have been edge trailing on a clean stone with no slurry until the stone starts to get glazed. Then I add a little more water but do not clean the pores out, then continue "stropping" on that stone until it's dry. Seems to give me the best results so far.

It all depends on the stone in my experience, and the grit value of course. Nearly all of my waterstones can be backhoned on with a trailing pass without any undue burr formation, as well as all of my jointer stones - with or without a slurry or mud, so the slurry isn't mandatory. That isn't to say the abrasives don't have some mobility though would be tough to isolate the effect. Can also manage a bunch of trailing passes on sandpaper and lapping film but doesn't seem to have quite the same effect as on a harder surface.

There's a threshold of stone density, binder percentage, particle mobility among other factors, but I am not certain what it is except on a case by case basis. I know I have poor results finish backhoning on diamonds, India stones, Arkansas stones, ceramics, even silicon carbide stones. Yet these same abrasives in a different binder all work fine to excellent. Is something I'm always tinkering with...

 

[HeavyHanded]

I'm definitely missing something here.
These are a couple of images from a straight razor finished edge-leading on a DMT 325 with water. I don't see teeth, and it's not obvious to me that the direction of the scratches would affect the cutting performance.

In the pics it looks to me like the crossing effect is diminishing the amount of tooth. As the finish becomes finer the effect would expect to decrease somewhat, at least on most materials/cut tests. The scales for these are in the upper left by the red bar.

 

[REK Knives]

^ great photos to illustrate the point

 

[samuraistuart]

I thought I should add this caveat about my comment on stropping......

You guys are more than likely (I can promise it actually) producing edges WAY keener than I am. Some of you are straight razor guys, and sharpen them to perfection! I have never sharpened a straight razor, which I could see stropping being almost mandatory. Usually I go to 12k max on knives like kitchen knives, but recently acquired a few PSA lapping sheets in .3 micron and .05 micron. I did a few edge trailing strokes on these films after the 12k chinese stone (this was a petty kitchen knife in AEB-L at 61.5).

Before the lapping film I could cut a hair in half still on my arm. After the lapping film, I could whittle a hair on my arm! It would instantly catch the hair and split it down the middle! I kid you not! That was BY FAR the sharpest I have EVER sharpened anything in my life! I was quite pleased!

Ya'll probably do that regularly!

 

[ToddS]

OK, I can see a more tooth-like structure when the scratches are parallel. What is the hone in those images?