Next stone to get after Shapton 1k pro?

[daveb]

Because the difference between the SP1000 (acts like a 700ish stone) and SP2000 (acts like a 3000+ stone) is pretty wide. The SG2000 acts like a 2K. Doable? Yes.

SP1000 followed by a SG3000 would give you a better finish that the SG2000.

FWIW my roadie kit to sharpen friends knives - when I know they have Shun and Shun Lite, includes SG500, and SG3000 to be used together. .

 

[kujaku]

Is there a reason you guys rec sp2k and not sg2k?

I have never used SG in Japan because they are too expensive(SP2k $28, SG2k $85, NP3k $70).
According to Shapton, the recently released Rockstar, is basically the same as the SG. It is twice as thick and less than 1/2 the price.

 

[benomatic42]

IIRC the SP1k is quite a bit coarser than indicated, around 700 JIS, the Japanese standard. The Chosera / Naniwa Pro 3k is finer than it indicates, about 4k JIS. The jump is not impossible, but I would first try with a Shapton Pro 2k in between. The SP2k is a very nice, convenient stone, allowing a very easy complete deburring.

What I learned in furniture school (chisels & planes, thus single side bevels), and translate to knives (double), sounds sane and differs slightly here (depending on bevel assumptions), so I'd like to hear the opinions here:

• "sharpen" (bring primary bevel) to 1-less than target grit, typically 1k
• "polish" secondary bevel at target grit; because you're removing so little material, can be 1-2 grit steps past primary (in this case, even up to 5k/6k stones, maybe 8k)
• when dull, re-polish secondary at same stone/angle
• every 3-5th time, re-sharpen primary bevel to 1k

This ignores some of the details/nuance of burr removal techniques, but AFAICT does not per se conflict with those, so long as none of them themselves create a "significant" secondary bevel. If so, then YMMV.

Thoughts?

 

[Strozzi]

Ouka is a great soaker, perfect stopping point for kitchen knives. Good polishing for a synthetic stone.

 

[paosquared]

Because the difference between the SP1000 (acts like a 700ish stone) and SP2000 (acts like a 3000+ stone) is pretty wide. The SG2000 acts like a 2K. Doable? Yes.

SP1000 followed by a SG3000 would give you a better finish that the SG2000.

FWIW my roadie kit to sharpen friends knives - when I know they have Shun and Shun Lite, includes SG500, and SG3000 to be used together. .

if the sp2000 and sg3000 are both acting like 3000, what do you mean by "better finish" ?

 

[tostadas]

All I need for my sharpening are SP1k, SP2k, BBW. I've used the SP2k and the SG2k. Both are fine, but the SP is cheaper and has more material.

1k is as toothy as I need or for minor bevel setting
2k leaves an aggressive finish but is refined. Great for stainless.
BBW is my preferred finish on my most used knives. Big area, splash and go, and perfect balance of refinement and bite.

 

[Seemore]

Here’s the Suehiro Ouka (3000DN) on Amazon for $45.00 - a very decent price. Amazon also shows quite a smaller one (3000-35) at $38.00. If you decide on this stone, go bigger. Seven bucks over the life of the stone is nothing, especially with your 240s.

https://www.amazon.com/Suehiro-Sell...f1d-43b2-a0d1-f0a90658ae0a&pd_rd_i=B07S8KHN94

 

[Benuser]

What I learned in furniture school (chisels & planes, thus single side bevels), and translate to knives (double), sounds sane and differs slightly here (depending on bevel assumptions), so I'd like to hear the opinions here:

• "sharpen" (bring primary bevel) to 1-less than target grit, typically 1k
• "polish" secondary bevel at target grit; because you're removing so little material, can be 1-2 grit steps past primary (in this case, even up to 5k/6k stones, maybe 8k)
• when dull, re-polish secondary at same stone/angle
• every 3-5th time, re-sharpen primary bevel to 1k

This ignores some of the details/nuance of burr removal techniques, but AFAICT does not per se conflict with those, so long as none of them themselves create a "significant" secondary bevel. If so, then YMMV.

Thoughts?

That's the technique advocated by Juranitch, some fifty years ago. Building the relief with a coarse grit, and the secondary — cutting — edge with the finest grit only. I must admit, it does work. However, it won't deliver a stable and lasting edge with other than very fine grained steel types, think the simplest carbons or a stainless like AEB-L. Most available steels today though will greatly benefit from a progression started with a medium coarse stone, raising a burr with that first stone, and deburring with every stone in the progression.

 

[benomatic42]

However, it won't deliver a stable and lasting edge with other than very fine grained steel types, think the simplest carbons or a stainless like AEB-L. Most available steels today though will greatly benefit from a progression started with a medium coarse stone, raising a burr with that first stone, and deburring with every stone in the progression.

Is there a metallurgical explanation for this? (Or a simply poor execution of a perfectly fine theory?)

It strikes me intuitively that if your fine (eg, my SP5k) polishes/cuts/grinds through the previous scratches to the base layer, and any fatigued metal/burr has already been removed, it ought to be the same quality of result.

I am definitely getting consistent sharpness off stones (both at 1k and 5k), but the retention is highly variable -- so I have already been trying both forms (going fully through with 5k), but I do not currently have a "tweener" stone, eg a SP2k or Ouka 3k.

 

[Benuser]

Try changing an edge geometry with Aogami Super, VG-10 or Global's Cromova using a 4k. It's perfectly possible, but won't hold. You will regret having skipped a 500.

 

[benomatic42]

Try changing an edge geometry with Aogami Super, VG-10 or Global's Cromova using a 4k. It's perfectly possible, but won't hold. You will regret having skipped a 500.

I'm sure the theory breaks down at some point - I don't imagine going from eg 320 → 4k simply because the depth of scratches vs depth of cut would seem too big. My space is more 1k → 5k, where already beginning at 1k should be a useable edge, and the 5k secondary bevel is icing on the cake.

 

[Seemore]

Try changing an edge geometry with Aogami Super, VG-10 or Global's Cromova using a 4k. It's perfectly possible, but won't hold.

Like many members, I follow conversations to see what I can learn, and I don’t want to hijack this thread. But could you explain why it won’t hold?

 

[Benuser]

Like many members, I follow conversations to see what I can learn, and I don’t want to hijack this thread. But could you explain why it won’t hold?

I can only see it poorly holds. My guess would be that fine stones can't abrade chromium carbides as coarse stones do.

 

[mengwong]

https://scienceofsharp.com/2015/07/09/its-too-big-of-a-jump/

It did take hundreds of strokes (on a freshly lapped 16k and with pressure) to remove the chips from the 320 with the 16k stone. This is arguably excessive, and putting a stone in the middle, say 1k or 2k, would likely reduce the number of strokes required. The key observation is that most of those hundreds of strokes are required to remove the large chips, which only occur when we use edge-leading strokes on the 320. If we use edge-trailing strokes on the 320, and then edge trailing, or back-and-forth strokes on the 16k, it is an easy transition. Second, the end result was the same, directly from 320 to 16k as when we insert 1k,2k,4k,8k stones between them.

I don’t pretend that I normally use these two particular stones in sequence, this is purely a demonstration.

Also note, this demonstration was performed with an 8 degree per side carbon-steel straight razor – I would not generalize these results, but use them as a starting point for your own experimentation.

 

[Mr.Wizard]

Is there a metallurgical explanation for this? (Or a simply poor execution of a perfectly fine theory?)

It strikes me intuitively that if your fine (eg, my SP5k) polishes/cuts/grinds through the previous scratches to the base layer, and any fatigued metal/burr has already been removed, it ought to be the same quality of result.

Because of sub-surface damage you would have to continue removing material even when all scratches are invisible. This is especially true if you are using a combination of steel and abrasive that produces burnishing, as this hides the scratches rather than removing them.

https://scienceofsharp.com/2019/10/02/grit-scratches-and-sub-surface-damage-part-1/

"Cross-section of a single scratch from 600 grit silicon carbide paper. The damaged steel is marked in red. The original surface is marked with the black line. The ploughed metal is observed as the red-marked area above the black line."

"Cross-section view of a 320 grit scratch that is partially filled by the metal displaced by subsequent scratches."

 

[pavlobee]

Because of sub-surface damage you would have to continue removing material even when all scratches are invisible. This is especially true if you are using a combination of steel and abrasive that produces burnishing, as this hides the scratches rather than removing them.

https://scienceofsharp.com/2019/10/02/grit-scratches-and-sub-surface-damage-part-1/

"Cross-section of a single scratch from 600 grit silicon carbide paper. The damaged steel is marked in red. The original surface is marked with the black line. The ploughed metal is observed as the red-marked area above the black line."

"Cross-section view of a 320 grit scratch that is partially filled by the metal displaced by subsequent scratches."

Very good demonstration that.

 

[benomatic42]

Because of sub-surface damage you would have to continue removing material even when all scratches are invisible. This is especially true if you are using a combination of steel and abrasive that produces burnishing, as this hides the scratches rather than removing them.

https://scienceofsharp.com/2019/10/02/grit-scratches-and-sub-surface-damage-part-1/

"Cross-section of a single scratch from 600 grit silicon carbide paper. The damaged steel is marked in red. The original surface is marked with the black line. The ploughed metal is observed as the red-marked area above the black line."

If the damage runs that deep, can it be avoided with any sequence at all?

At the end of the article he acknowledges this intuitive question, and whether that actually matters:

Generally, we have observed that damage typically extends well below the depth of the surface roughness. We must expect that when sharpening with all but the finest polishing grit, the apex will therefore consist of damaged steel. The obvious question is what are the properties of this modified steel? In particular, is it less brittle and more likely to deform than chip?

This sheds light on things, but doesn't really provide real focus on the practical question of grit sequence. It may be that bigger grit jumps on eg secondary bevels fail to cut through the upper 3rd of scratches, and therefore leave a weaker surface/apex. Depending on the grit/pressure, it's quite reasonable given his quote slightly earlier:

With the Shapton Glass 2k (nominally 7.35 micron), in Abrasion Rate vs Grit, I measured an average removal rate of only 0.02 microns per pass across the stone. At the same time (and under the same conditions), we observe individual scratches that are up to 0.5 microns deep.

So my takeaway would be that it's less likely the damaged sub-structure, and more the question of whether subsequent passes cut through the messy upper layer.


I think I'll add a 2k stone to my sequence and start trying with and without

 

[Mr.Wizard]

If the damage runs that deep, can it be avoided with any sequence at all?

This sheds light on things, but doesn't really provide real focus on the practice question of grit sequence. It may be that bigger grit jumps on eg secondary bevels fail to cut through the upper 3rd of scratches, and therefore leave a weaker surface/apex.

In metallographic sample preparation change to grain structure must be minimized, so their polishing sequences and times are a good place look if we set this as a goal. In general I see finer abrasives, lower pressure, and a longer polishing time.

https://www.metallographic.com/Metallographic-Preparation-Procedures/1095-quenched-steel.htm

https://vacaero.com/information-res...n-for-electron-backscattered-diffraction.html

https://www.kemet.co.uk/blog/metallography/metallographic-specimen-preparation

https://www.buehler.com/sumMet.php?material=Iron
https://www.calameo.com/buehler/read/006393291a14f7be86036

Abrasive/surface	Lubricant	Force/ sample	Speed (Head/base)	Time	Individual Force mode	Central Force mode
120 grit SiC paper* 240 grit SiC paper*	Water	5-10 lbs	200/200 rpm	Planar 1 min
360 grit SiC paper 600 grit SiC paper	Water	5-10 lbs	200/200 rpm	1 min 1 min
9 um DIAMAT diamond on POLYPAD polishing pad	DIALUBE Purple Extender	5 lbs	200/200 rpm	3 min
3 um DIAMAT diamond on TEXPAN polishing pad	DIALUBE Purple Extender	5 lbs	200/200 rpm	3 min
1 um DIAMAT diamond on GOLDPAD polishing pad	DIALUBE Purple Extender	5-10 lbs	200/200 rpm	2 min
0.05 um Nanometer alumina on MICROPAD polishing pad		5 lbs	100/100 rpm	30 sec

Surface	Abrasive / Size	Load - lbs [N] / Specimen	Base Speed [rpm]	Relative Rotation	Time [min:sec]
CarbiMet	320 [P400] grit SiC water cooled	6 [27]	300		Until Plane
UltraPad	9 µm MetaDi Supreme Diamond	6 [27]	150		5:00
TriDent	3 µm MetaDi Supreme Diamond	6 [27]	150		3:00
MicroCloth	0.05 µm MasterPrep Alumina	6 [27]	150		2:00