Scratch pattern when sharpening

[HeavyHanded]

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

The first image is 800 grit 3M wet/dry over a Washboard - 420HC, second is 320 grit Gator wet/dry over Washboard - Aus 8. Third image is off of a fine Crystalon and steeled with a smooth meatpacker's steel - that's how it has the heavily burnished features along the edge - not sure what steel, maybe Sandvik 12c27. The last image is off of a fine Spyderco ceramic and stropped on plain leather - maybe stropped with Flexcut Gold first but I don't think so - 1095.

 

[ToddS]

I tried honing a razor one a DMT 1200 at 45 degrees. Is this toothy?

 

[Jason B.]

A razor is not going to give the best example of a toothy edge. Knives and razors don't take the same edge.

 

[Spey]

I tried honing a razor one a DMT 1200 at 45 degrees. Is this toothy?

It appears from my perspective that the "toothy" edge is there (and has been, but being hidden by other factors), and it is becoming more evident as your strokes and resultant scratch pattern are evolving into more parallel strokes/pattern.

After your first images I was thinking the non-parallel stroke/scratch was really interrupting an even edge pattern. Others I think also picked up on this.

When the strokes pattern changes is when the wavy edge fallout is happening (from my experience, this I'd what I am seeing as the photos are evolving through this thread). The photos in this thread appear to confirm this and are similar to my experiences.

Additionally, as the pattern is becoming more consistent (in recent posts) it appears other things are showing themselves (that were also contributors to earlier photos of uneven wavey edge).

Appears either the stone(s) have differential grit size or metal swarth buildup is causing irregular scratch depth & pattern. Possibly your stone(s) need surfacing (or evening - typical on my DMT's and especially my last Tan 8k DTM that took surfacibg & few sharpening to finally calm down & smooth out).

As far as swarth build up on stones, cleaning the stones comes to mind first. I clean my DMT's minimally after each sharpening and typically progressively as they are being used on a knife (each grit cleaned before moving blade sides and also b4 the last few light passes on each edge. I have typically just scrubbed them under water with a little soap, and have recently began using a strong magnet to pull the steel swarth from my diamond stones.

Some knives don't get this same level of attention (stone cleaning during sharpening). But, the one's that do seem to have noticeably superior edge retention, life, and reduced maintenance. Effectively, a better life-cycle-sharpening-time-value, provided the user does not abuse the edge (cutting on ceramic plates, impacting staples, concrete, etc :-o

I think also, as other have stated, the specific metal you are sharpening on may also be contributor factor to your results.

Hopefully something here is of some value. Wonderful imagery! Looking fwd to following this threads progression as very interested to "see" how the answers evolve.

Regards & thanks,
Chris

 

[Spey]

Oh, (hope I don't get throw under the bus for this one) I have also had issues of magnetism hold metal filing on the blade during sharpening effectively disrupting consistent scratch patterns. I do not think I have read anywhere about this, but it can be a PITA sometimes to deal with (keeping blade & stones clean during sharpening).

 

[HeavyHanded]

I tried honing a razor one a DMT 1200 at 45 degrees. Is this toothy?

I'd say those qualify as toothy. As you continue to go up in polish the edge will become more uniform, not just along the edge as viewed from the side, but also as viewed from above.

 

[REK Knives]

I'd say those qualify as toothy. As you continue to go up in polish the edge will become more uniform, not just along the edge as viewed from the side, but also as viewed from above.

I agree. There would be a semi simple test to test the effectiveness of how the angles of the "teeth" affect performance. It would require some type of postage scale and hemp rope, and then seeing what the least amount of pressure can be used for a certain section of a blade to cut through the hemp, both on a draw-slicing cut and a push-slicing cut. i really need to make something but haven't had the time.

 

[ToddS]

Oh, (hope I don't get throw under the bus for this one) I have also had issues of magnetism hold metal filing on the blade during sharpening effectively disrupting consistent scratch patterns. I do not think I have read anywhere about this, but it can be a PITA sometimes to deal with (keeping blade & stones clean during sharpening).

The blade I use for many of my experiments becomes magnetized from honing. The magnetic field deflects and distorts the electron image in a way that is obvious to me when I am imaging. I have to degauss the blade occasionally to remove the magnetism.

 

[ToddS]

Should a DMT 325 produce a toothy edge? If anyone has micrographs of scratches from a 325 and 1200, I would appreciate seeing them.

 

[HeavyHanded]

I agree. There would be a semi simple test to test the effectiveness of how the angles of the "teeth" affect performance. It would require some type of postage scale and hemp rope, and then seeing what the least amount of pressure can be used for a certain section of a blade to cut through the hemp, both on a draw-slicing cut and a push-slicing cut. i really need to make something but haven't had the time.

You can do some anecdotal testing very easy, just use a light weight knife and swap it end for end on a few tests with drawing cuts - this will eliminate any inherent mechanical advantage one might have based on how the knife is held.

 

[Obsessed with Edges]

Should a DMT 325 produce a toothy edge? If anyone has micrographs of scratches from a 325 and 1200, I would appreciate seeing them.

I don't have micrographs, but to me, a DMT 325 (45µ grit) is WAAAYYY toothy, even with the lightest touch (compare to DMT 1200 @ 9µ). Such an edge can be a very good thing, depending on how it's used. I'd think SEM micrographs of such an edge would roughly resemble the Grand Tetons.


David

 

[ToddS]

I don't have micrographs, but to me, a DMT 325 (45µ grit) is WAAAYYY toothy, even with the lightest touch (compare to DMT 1200 @ 9µ). Such an edge can be a very good thing, depending on how it's used. I'd think SEM micrographs of such an edge would roughly resemble the Grand Tetons.


David

I would have thought so also, HOWEVER, these are SEM micrographs of a DMT 325 edge:

 

[Obsessed with Edges]

I would have thought so also, HOWEVER, these are SEM micrographs of a DMT 325 edge:

This might touch on what Jason mentioned earlier, in that knives & razors may not take the same edge on a given hone, maybe(?) due to vast differences in edge geometry/thickness and how they're sharpened (angle & use of pressure, maybe direction of stroke as well). Might be an apples vs. oranges sort of thing.

Are the images from edge-leading* passes, or edge-trailing? I could see, if trailing passes were used at very low angle (as for razors), the depth of cut could be much more shallow, more or less 'skimming' over the diamond. I'd think edge-leading passes on a coarse DMT might wreck such a thin edge on a razor, especially if sharpened in a manner similar to a more typical knife edge, at higher angle and edge-leading.

Edit:
(* = Looking at your post#14 earlier, I see you mentioned edge-leading passes. I'm thinking the differences in teeth, or lack of, might be due to the really ragged parts along the edge breaking or stripping away during honing, or folding back underneath because the cross-section is so thin at the edge, as opposed to the more ragged 'teeth' being fixed in place, as would be expected on a thicker-edged blade with a stronger cross-section. That's the only thing that makes sense to me.)


David

 

[ToddS]

These are all edge leading strokes with light pressure.
The only effect I observed with increasing pressure was the production of a few chips. The edge between the chips seems not to affected by the increased pressure.

This is an edge view after the DMT 600 (25 micron) with two chips and a 25 micron circle for scale:

 

[Obsessed with Edges]

These are all edge leading strokes with light pressure.
The only effect I observed with increasing pressure was the production of a few chips. The edge between the chips seems not to affected by the increased pressure.

Just occurred to me...

If this is still a straight razor in the image, was it sharpened in a manner typical for those, with the spine of the razor laid against the hone?

Reason I ask, with a conventional knife edge, ALL of the pressure is focused along the edge bevel, because it's the only area of contact. With a razor, if sharpening with the spine laying against the hone, pressure is distributed much more widely (against both spine and edge bevel), effectively reducing per-unit pressure, unless really leaning into it. If so, that might explain the (apparently) much shallower scratch pattern left by the Coarse DMT, as compared to using the same on a conventional knife edge. I know from my own experiences, when grinding the full side of a blade, as for thinning a primary grind, the hone used effectively becomes less aggressive, because pressure is so widely distributed; grinding becomes much slower this way, because it's not digging as deeply on each pass. Just a thought...


David

 

[Jason B.]

Razor edges and knife edges are not the same. The added hardness of the razor steel will greatly affect the fineness of the edge. Along with that not needing to hold any angle part.

Factory edge on a Richmond Gyuto, 154cm @ 61-62



Some more shots of the same knife sharpened on DMT diamond plates. Not sure what grits matches the photo, sorry. Should start at XXC and move to EEF though.

 

[Jason B.]

Due to the hardness of the steel and the fixed abrasive you can see where the edge has collided with the diamonds on the plate.



And this one I know is the DMT 8k.

 

[ToddS]

Thank-you for those images Jason, they are quite helpful to me.

I wasn't aware that there is much difference in the hardness of razors vs quality knives, I thought razors are usually in the 58-62 HRC range. ?

Certainly the lower angle results in a more flexible apex region.

As to pressure, razors usually have much narrower bevels than knives, so much less force is required to achieve the same pressure.

This have given me a couple of things to experiment with, however.

 

[samuraistuart]

knives and razors are often hardened to above 60. I have heard the harder the edge the sharper it can be made. But I have also been told, and I think it stands to reason, that once a certain RC has been reached, the edge is not going to be any sharper. What that RC value is, I am not sure, but would think around the mid to upper 50s if not closer to 60. As in a knife at 60 can be made much sharper than one at 50. But a knife at 64 really can't be made any sharper than one around 60. I dont mean as absolute. But I think it's close to right anyway.

 

[HeavyHanded]

Here's one off the DMT EF. Is Aus8 at 400x, scale is just under 4u, edge was stropped on plain paper wrapped around the same stone - interrupted surface.