The Anatomy of a Scratch or Scratch Geometry?

[RubiconSS]

As mentioned, I re-profiled my Acies ZDP-189 to 30* inclusive using the WEPS.
I do not have magnification other than that little illuminated portable microscope from Radio Shack. I don't need magnification to see the scratches in the bevel from the re-profiling.
My question is, in going back to now remove the scratches is it safe to assume that the finer grit paddles will in essence ride on the ridges of the scratches removing material down until the scratch is memoved?
If this logical assumption is correct - what methodology and what grit would you use to remove the scratches knowing that the bevel and angle is set.
I assume that by doing this process I may also get to this hair splitting smoothness as well. Because I can also assume that scratches translate to micro-serrations in the edge as well ( can't have a laser smooth edge with scratches I would think)
Lots of stuff in there but bottom line is smoothing out the edge and mirroring the bevel.

 

[RubiconSS]

In reading through all my search hits I believe Obsessed touched on this, correct me if I read wrong OWE's.
Start back at about 600 grit and really work each level (to what degree will be the mystery) maybe go by sound.
I might go out and buy a microscope because I really think seeing would be helpful.
I think this super hard steel fractures more at the edge during the initial grinding.

 

[unit]

As mentioned, I re-profiled my Acies ZDP-189 to 30* inclusive using the WEPS.
I do not have magnification other than that little illuminated portable microscope from Radio Shack. I don't need magnification to see the scratches in the bevel from the re-profiling.
My question is, in going back to now remove the scratches is it safe to assume that the finer grit paddles will in essence ride on the ridges of the scratches removing material down until the scratch is memoved?
If this logical assumption is correct - what methodology and what grit would you use to remove the scratches knowing that the bevel and angle is set.
I assume that by doing this process I may also get to this hair splitting smoothness as well. Because I can also assume that scratches translate to micro-serrations in the edge as well ( can't have a laser smooth edge with scratches I would think)
Lots of stuff in there but bottom line is smoothing out the edge and mirroring the bevel.

I am not sure exactly what you are asking entirely, but with regard to the scratches...the general idea is to estimate the size of the scratches in terms of your abrasives. Are the scratches consistent with the size of the scratches your Fine abrasive? If so, use your next finest abrasive to remove them...anything finer and you are going to invest more time than is necessary, anything coarser and you will be adding more scratches that are bigger (thus going backwards in your race to the finish).

Regarding a hair splitting edge...it should already be VERY sharp if you polished it and only failed to remove a few scratches.

 

[unit]

In reading through all my search hits I believe Obsessed touched on this, correct me if I read wrong OWE's.
Start back at about 600 grit and really work each level (to what degree will be the mystery) maybe go by sound.
I might go out and buy a microscope because I really think seeing would be helpful.
I think this super hard steel fractures more at the edge during the initial grinding.

I apologize, but I am getting confused (and I am not sure what you are getting at...so if I sound ignorant, just disregard).

I have done some extensive grinding on ZDP-189 (Spyderco) and have not seen any evidence of fracturing. The blades I have worked on were (I think) reported to be at or near Rc 65.

 

[RubiconSS]

I am not sure exactly what you are asking entirely, but with regard to the scratches...the general idea is to estimate the size of the scratches in terms of your abrasives. Are the scratches consistent with the size of the scratches your Fine abrasive? If so, use your next finest abrasive to remove them...anything finer and you are going to invest more time than is necessary, anything coarser and you will be adding more scratches that are bigger (thus going backwards in your race to the finish).

Regarding a hair splitting edge...it should already be VERY sharp if you polished it and only failed to remove a few scratches.

Fair enough, Asking:
- Do scratches run all the way to the edge and serve as indicators that there are probably micro-serrations in the edge?
- With the WEPS, is it adviseable to start at approximately 600 when going after the scratches then moving slowly with each step thereafter?
- Do the harder steels like ZDP-189 fracture more at the edge apex?
Some of these are more discussion based questions -vs- yes/no. I find that with this group much ancillary knowledge is imparted with those types of thread topics.
As always, input appreciated.

 

[RubiconSS]

I apologize, but I am getting confused (and I am not sure what you are getting at...so if I sound ignorant, just disregard).

I have done some extensive grinding on ZDP-189 (Spyderco) and have not seen any evidence of fracturing. The blades I have worked on were (I think) reported to be at or near Rc 65.

My observation differs, I have sharpened several knives and the ZDP-189 almost seemed to be "powdering" during the 100 grit phase. Very different material coming off than my softer steels which came off in micro shavings.
My term "fracturing" is just an attempt at an adjective to describe what I was seeing.

Honestly. it may have been material coming off the actual 100 grit paddle because of the hard steel. May have been diamond powder.

 

[unit]

- Do scratches run all the way to the edge and serve as indicators that there are probably micro-serrations in the edge?

It depends...the only way to tell is to get a scope and see. It is possible, but not at all certain that the scratches will all extend to the edge. If they extend to the edge, it certainly seems conceivable that they would offer a serration effect.

- With the WEPS, is it adviseable to start at approximately 600 when going after the scratches then moving slowly with each step thereafter?

I am not familiar with WEPS, but I would say that it is best to start with the a particle (grit) size JUST BARELY smaller than the largest scratches. I find that some factors are critical with this steel. Generally, you need REALLY low pressure between the abrasive and the blade, and each step in the grit progression takes longer than the previous step.

- Do the harder steels like ZDP-189 fracture more at the edge apex?

Not in my findings, but I never go coarser than 220 grit, and I use LOW pressure...YMMV

 

[unit]

Honestly. it may have been material coming off the actual 100 grit paddle because of the hard steel. May have been diamond powder.

This would be my fear. ZDP is generally run quite hard...and is effective at high hardness, but you can not muscle it with abrasives...because it might win the fight

 

[RubiconSS]

This would be my fear. ZDP is generally run quite hard...and is effective at high hardness, but you can not muscle it with abrasives...because it might win the fight

I think that may have been it. Every new system still has some learning curve and with me sometimes it takes a little bit before it sinks in. The lightness of the touch is my challenge at this point.

 

[Obsessed with Edges]

I am not sure exactly what you are asking entirely, but with regard to the scratches...the general idea is to estimate the size of the scratches in terms of your abrasives. Are the scratches consistent with the size of the scratches your Fine abrasive? If so, use your next finest abrasive to remove them...anything finer and you are going to invest more time than is necessary, anything coarser and you will be adding more scratches that are bigger (thus going backwards in your race to the finish).

Regarding a hair splitting edge...it should already be VERY sharp if you polished it and only failed to remove a few scratches.

:thumbup:

That pretty much sums up what I'd do. Regardless of which method you are using, the basic idea with each grit succession is to remove the scratches from the previous grit step. So, based upon how wide/deep the scratches are, you make a grit choice one step step finer than that, to remove those scratches. This will help to ensure that you remove those scratches relatively quickly, without overdoing it (by going too coarse).

I haven't used the WEPS, but if this were being done with sandpaper in a grit sequence of say, 220/320/400/600/800/etc., and the scratches you're seeing look like they might've been left by the 320 or so, I'd begin with the 400 grit to start removing them. If it's taking too long at that grit, chances are the scratches are coarser than 320. So, take a step back (to 320) and remove what are likely scratches from the 220. Once you've found the right grit to remove those scratches effectively, then proceed back up through the grit sequence. That's basically how it should go.

And, as is ALWAYS good sharpening practice, go LIGHT with the pressure and take it easy. Sounds cliche, but it always rings true: LET THE GRIT DO THE WORK. This is all the more important when working with extra hard steels (especially with diamond hones). Too much pressure can chip the edge, and will also scrub diamond off of the hone, shortening it's life considerably.

Hope this is helpful. Good luck.

 

[RubiconSS]

It's just one of those things. Like trying to describe the color - Blue.

Trying to describe " a light touch". I am experimenting and it seems as though it is working.
The knives look great and are very sharp. But hey, gotta have something to talk about.

 

[pwet]

i'd say that when you struggle to keep the stone in contact because you're too light .... you're in the good way.

 

[Obsessed with Edges]

i'd say that when you struggle to keep the stone in contact because you're too light .... you're in the good way.

Bingo.

When I was using my Lansky sharpener, I maintained just (barely) enough pressure to keep the hone from skipping/bouncing across the edge. Anything more than that, is too heavy.

Something that helped me, was to position my index finger on the back of the hone, while supporting the hone at the sides, using my thumb & middle finger. I relied upon the 'feel' I was getting from the 'pad' of my index finger, to get as much feedback as possible from the hone. If I applied too much pressure with my index finger, much of that 'feel' goes away. Keeping it light (very) helped to enhance that feel. Sort of as if I was trying to detect a grain of sand between two hard surfaces, by feeling the vibrations through the back, with the pad of my finger.

Also helps to go VERY SLOW with the stroke, to get used to the 'feel' aspect. SLOW is a good thing anyway, makes for better control.

 

[Jason B.]

Skipping to the next stone too quickly reduces the effectiveness of each following grit. Because its a smaller grit it always starts by removing the ridges of the previous scratch pattern. Once the ridges have been leveled to the valley of the larger scratch the finer abrasive then produces it's own scratch pattern of peaks and valleys. This process repeats itself with each step just on a smaller scale each time.

When you get to the 1-3 micron range you start to get to the point where a scratch pattern is hardly visible by the human eye. If at any point a step was rushed or a spot in the bevel neglected it will stick out like a sore thumb in contrast to the better finished areas. To fix areas that this happens in I start by guessing the grit of the scratch and work my way back to the stone that would have followed. Its always better to start with a higher grit than go to the suspected grit, you save on excess metal removal and your not trying to equal the scratch just remove it.

The "teeth" as they are often described at the apex of a bevel are metal deformations or the ending of the peaks of a scratch. I like to use clay as a example because it shows on a larger scale the effects of a scratch and deformation. If you take a block of clay and scratch the surface with a nail or other sharp object the surface will no longer be flat. Obviously the valley of the scratch will be deeper but the peaks are raised above the surface, this is a deformation around the cut of the scratch. If the scratch is extended to a 90 degree edge the material in front of the cutting tip (abrasive) is sheered sending material deformations in all direction of pressure. The peaks of the scratch will be more in line and straight extension from the apex of the corner while the valley or "cut" of the scratch will have less of a deformation and will be bent towards the other slope.

Its been my observation through high magnification that as the abrasive becomes smaller so does the amount of deformation. To a point where the surface and apex become one clean and solid object.

I think some SEM photos at 10,000x might tell us more but that's just getting obsessive

 

[RubiconSS]

I knew it would happen, see? You guys came in and found me banging around in a dark room and - Turned the lights on.
ALL is clear now.
I now get "light touch" AND the mystery of the scratch has been solved better than that electron microscope I picked up at the neighbors garage sale could have done.
I feel like dancing - maybe after my nap!
Thank you

 

[unit]

I knew it would happen, see? You guys came in and found me banging around in a dark room and - Turned the lights on.
ALL is clear now.
I now get "light touch" AND the mystery of the scratch has been solved better than that electron microscope I picked up at the neighbors garage sale could have done.
I feel like dancing - maybe after my nap!
Thank you

Glad it all worked out. This place is a pretty good spot to find help. Sometimes you have to sort through some opinions, but in the end, there are a lot of nice and helpful people here!

 

[RubiconSS]

Glad it all worked out. This place is a pretty good spot to find help. Sometimes you have to sort through some opinions, but in the end, there are a lot of nice and helpful people here!

Yes. To me it is the place to be for the real knife lover. I get tired of " hey look at my new knife" threads. That's just my opinion. I am interested in knives. What they do and what you are able to do with them. So for me - here is where it is.

 

[Obsessed with Edges]

I knew it would happen, see? You guys came in and found me banging around in a dark room and - Turned the lights on.
ALL is clear now.
I now get "light touch" AND the mystery of the scratch has been solved better than that electron microscope I picked up at the neighbors garage sale could have done.
I feel like dancing - maybe after my nap!
Thank you

This thread is a good example of what ideally can take place, when somebody has a question. In addition to answering a particular question, there are always more pearls to be found, from multiple perspectives. Always something new to be learned. It's why I like hangin' around here.

Glad to hear that it has paid off. :thumbup: