Sharpening high hardness and wear resistant steels

[BluntCut MetalWorks]

I intended to make a quick video while sharpening knives to be ship... major failed on the 'quickly' part - over 23 minutes long

In the video, I sharpen a thin 67rc CPM 10V Hunter knife with behind edge thickness around 0.006". Basically, try to produce a durable sharp edge with less than $50 sharpening gear: 2 SiC waterstone, DMT dia-fold.

When edge shoulder is really thin, actually cutting performance doesn't degrade much with wobbly angle less than 20dps. Well, at least my nonchalant morning mode anyway.

Perspective on my yakking - fwiw and spoonka-salt :barf:

[video=youtube_share;XRBburCfnkE]http://youtu.be/XRBburCfnkE[/video]

 

[malaverdiere]

Thanks for sharing your video!

Quick question. In your video, you mention wearing out your diamond stones, so you suggest SiC stones instead.
Have you tried the Japanese waterstones? How do they compare to SiC?

 

[BluntCut MetalWorks]

Envision a fixed diamond on the plate/stone - repeated use will eventually dull or lost it, multiple ways to arrive at this state. e.g. high pressure collision with carbide and loose diamond particle, dislodge from plate, partial fractured (poly diamond, abrasive point is shorter than others), etc... Fixed = non-renewable/refresh grit. In order to effectively abrade with dull abrasive, you need to use high pressure. Well, nasty spiral way to kill both diamond plate and apex. SiC stone easy exposure new sharp grit. Just aware that harder SiC will glaze over (aka dull/polished/rounded SiC on surface), so doping/lapping with loose sharp SiC to remove glaze layer.

Common waterstone (Japanese included) abrasive is alumina (Aluminum Oxide - type of ceramic but not super hard). Of course there are SiC and ceramic particle types. For AlO grit, once above 240 on hard stone - it mostly glaze/polish over by 10V carbides. Sure, high pressure will abrade but also burnish&possibly damage near apex. It wouldn't be effective to shape a rock(VC) using a baseball bat(AlO)

Sometime, other sharpeners allude to fact that a very coarse SiC/diamond can sharpened to hair whittling edge. Well, using sharp + sparse abrasive with feather pressure = low psi and low density cutting points = aka simulated smaller abrasive albeit guessing on pressure amt (depend on abrasive population). Much faster just use smaller abrasive, thereby 3um dmt EE plate is handy.

Thanks for sharing your video!

Quick question. In your video, you mention wearing out your diamond stones, so you suggest SiC stones instead.
Have you tried the Japanese waterstones? How do they compare to SiC?

 

[BluntCut MetalWorks]

Pertaining to high vanadium carbide volume steels

Often we use a crutch 'quickly degrade to working edge' to describe how a very keen edge degraded to less keen. Is it a practical compromise or justification for poor result or both?

A strong & durable apex would consists of precise shaped matrix & carbides. When apex sharpened to sub-micron but quickly degraded to 2+um wide after non-impact usage. Where same same edge geometry from 52100 would retain its sub-micron apex radius. 'Working edge' = present of carbides before that the apex is mostly consist of matrix material and probably weakened & jagged because sharpening failure to shape carbides decorating the apex. I finished with fixed ~3um (mesh) because well shaped VC will keep high keenness longer and very gradual degradation to working edge.

Ideally we want stone surface (for various grit size) to flat, abrasive be uniform in size & distribution & higher density & keep cutting edge sharp longer. Sort of response to SamuraiStuart - for fixed abrasive smaller than 6um, surface of DMT ME & EE or whichever are not going to flat. So, I break-in these surface before use. I crush the surface burrs (high cluster/clump), first with mild steel rod, wash, ceramic rod, wash, rub with glass, wash, gentle rub with carbide scrapper, wash. OK, early scratches still be deeper but not crazy *as-bought*.

Furthermore keep in mind, cutting/abrading depth from grit with dia N microns probably/mostly (depends on steel resistance to penetration and cutter sharpeness & geometry) in range of N/20 to N/5. Excess depth (says N/x, where x is less than 4) would risk dislodge abrasive from substrate/binder/plate.

 

[bodog]

Luong, why do you think higher hardness, carbide rich steel would degrade diamond plates faster than low hardness, low carbide steels or low hardness, carbide rich steel? I think people just get impatient and push harder.

I'd like to see someone take some ceramic or alox stones and shape them with diamond and sic stones. I truly don't believe the diamonds would fail faster unless, like you said, there were poly diamonds being used and they break apart or someone uses too much pressure. If someone used quality monocrystalline diamond stones and used appropriate pressure I genuinely believe the diamond would last longer. The only difference is that a diamond hone never refreshes its abrasives while with wear sic stones do.

After rambling, I believe both have their uses. For me and my uses, I don't really need sic stones anymore. I'd rather use good alox or sic sandpaper/belts for big jobs like thinning a bevel and/or major reprofiling or removing big chips and for things like easy sharpening, diamonds.

 

[BluntCut MetalWorks]

True in part (% is inverse proportional to skills). That to say, very high skills sharpener likely to keep more/less same pressure. So the other part is also increase in pressure but not readily apparent (until a quick doh!) Pressure = Force/Contact-Area. High strength and high carbides combination resist/reduce abrasive penetration depth. So if same F and penetration is only 1/3 as deep, Pressure is 3 times. And easily we might not take impact-force from stroke movement into account - when move through a field with higher hard carbides/particles, impact force increase proportional to carbide volume. See there are quite a few ways to dull fixed diamond surface, even for highly skills sharpeners.

Luong, why do you think higher hardness, carbide rich steel would degrade diamond plates faster than low hardness, low carbide steels or low hardness, carbide rich steel? I think people just get impatient and push harder.

Poly crystal can slowly fractured into almost rounded shape, instead of sharp jagged cubic (per see). Both mono & poly would last but certainly will get dulled over time. My AlO 60-220 stones mostly flake off or glaze when I try to grind 67+rc 10V. Thus far only my 12" long 60-80grit SiC stone doesn't glaze over but hahaha VFD 2x72 ceramic belt to prep for 120 grit SiC stone minor grinding/finishing.

I'd like to see someone take some ceramic or alox stones and shape them with diamond and sic stones. I truly don't believe the diamonds would fail faster unless, like you said, there were poly diamonds being used and they break apart or someone uses too much pressure. If someone used quality monocrystalline diamond stones and used appropriate pressure I genuinely believe the diamond would last longer. The only difference is that a diamond hone never refreshes its abrasives while with wear sic stones do.

After rambling, I believe both have their uses. For me and my uses, I don't really need sic stones anymore. I'd rather use good alox or sic sandpaper/belts for big jobs like thinning a bevel and/or major reprofiling or removing big chips and for things like easy sharpening, diamonds.

 

[Chris "Anagarika"]

Luong,

Haven't chanced to watch video, but your explanation (and in the meat cutter thread), somehow convinced me that BCMW CWF 10V is the correct utility kitchen knife. :thumbup:
I like my DMT EE with baby oil & light pressure.

 

[BluntCut MetalWorks]

Thanks Chris!

63+rc and sufficiently tough 10V, D2, W2, AEBL,.. with BET less than 0.01" thick, 10-15dps (depend on steel and finished grit for intended tasks) = good fits for kitchen util. 65rc aebl is slightly less tough compare to 10V 68rc but it's stainless and very easy to get screaming sharp - 3% Cr7C3 carbide volume sure beat 3% Fe3C in W2/1095 in wear resistance front.

With your EE practice, E/EE diafold will last a long time. My strong hand impatienceness gives diamond plates as short life span.

Luong,

Haven't chanced to watch video, but your explanation (and in the meat cutter thread), somehow convinced me that BCMW CWF 10V is the correct utility kitchen knife. :thumbup:
I like my DMT EE with baby oil & light pressure.

 

[Chris "Anagarika"]

Luong,

Yes, the AEBL is so easy getting screaming sharp & W2 as well. Thank you!
Between these, I might not need anything else, but one can also follow 'want' instead of 'need '

The 400/800 dark green/green stone looks similar to ACE China imported stone I have, I suspect is Taedea labeled 400/1000 on mine. I see you also renewed your EE/E diafold.

Thanks for sharing your thoughts on diamond burnishing that won't work for high VC.

 

[awestib]

Interesting stuff. Thinking of Todd's great scienceofsharp website, I wonder how the edge of CM 10V would respond to DMT coarse first (maybe also edge trailing to have a bit more metal beyond the apex ), then strop on denim with Mother's Mag? Do you think there is any significant abrasion going on with this metal polish on denim? In addition, assuming the same pressure, finer diamond cut deeper and may disturb the edge more than a coarser diamond (DMT coarse for instance) at least on carbon steel blades. Are we really producing keener/sharper edges with finer diamonds?

P.s. Have not had a chance to congratulate you to your first "production" knives Luong! Sent an email too ...

 

[BluntCut MetalWorks]

After DMT coarse, surface will has deep scratches/gashes and micro-serrated apex and along with weaken steel part (matrix clump and individual carbide as well). IME (with visual 400x metallurgical microscope) after stropped with leather loaded with white compound = minor polished surface and cleanup, what most shocking was how waxy grit filled up most of depressed/dipped/troughs of the surface. The smooth + quiet cutting feel/sound after stropped mainly due to wax and less rough surface. I never tried Mother Mag before(deducted/guess) but it has same waxy but less thick (viscous rather than solid like in bar form).

To confirm for oneself - just sharpen a carbide scrapper to different level of finishes and look under 100x magnification. IME - every time!

This where Todd_ScienceSharp EM images can put doubts to rest.

Interesting stuff. Thinking of Todd's great scienceofsharp website, I wonder how the edge of CM 10V would respond to DMT coarse first (maybe also edge trailing to have a bit more metal beyond the apex ), then strop on denim with Mother's Mag? Do you think there is any significant abrasion going on with this metal polish on denim? In addition, assuming the same pressure, finer diamond cut deeper and may disturb the edge more than a coarser diamond (DMT coarse for instance) at least on carbon steel blades. Are we really producing keener/sharper edges with finer diamonds?

Thanks Andy!

P.s. Have not had a chance to congratulate you to your first "production" knives Luong! Sent an email too ...

I am so behind with deadlines but (yes the 'but(s)') I need to wrap up planned fs knives this weekend rather let them dangling until 2017.

 

[HeavyHanded]

When working on diamond plate I now use mostly trailing pass, or at least emphasis is 80% trailing to preserve diamond surface. I actually do this with most of my sharpening media, only doing leading edge/emphasis leading edge to deburr or to keep burr formation lessened when grinding new bevel.

This has increased my appreciation of coarse waterstones dramatically, as I used to borderline hate these stones.

Re the plugging effect of the binder, I always finish with a few passes on plain paper, with high carbide steel this is mostly to clean and shine any burrs. Always there are streaks on the paper even if its wiped well before hand.

I normally don't much care for stropping high carbide steels in any event, but sometimes the job calls for a more refined edge and if the tool in question happens to be high carbide...

And another congrats to your product launch! Great looking stuff!

 

[BluntCut MetalWorks]

Thanks HH!

You are way ahead of me with R&D on sharpening with diamond & other abrasives. Lately, I just edge trailing on 800 grit SiC stone then hit with diamond grits (size, depends on targeted finishing level). I've denim on your washboard loaded white compound to quiet the cut and another WB bed sheet loaded with 0.25um diamond to scare toucher when touch the apex.

As Chris noticed - I bought new diafold e/ee. I still prefer edge leading, even mean dulling my diamond plate.
==Luong

When working on diamond plate I now use mostly trailing pass, or at least emphasis is 80% trailing to preserve diamond surface. I actually do this with most of my sharpening media, only doing leading edge/emphasis leading edge to deburr or to keep burr formation lessened when grinding new bevel.

This has increased my appreciation of coarse waterstones dramatically, as I used to borderline hate these stones.

Re the plugging effect of the binder, I always finish with a few passes on plain paper, with high carbide steel this is mostly to clean and shine any burrs. Always there are streaks on the paper even if its wiped well before hand.

I normally don't much care for stropping high carbide steels in any event, but sometimes the job calls for a more refined edge and if the tool in question happens to be high carbide...

And another congrats to your product launch! Great looking stuff!

 

[Chris "Anagarika"]

Wow. Much learning ahead.
Trailing on diamond? I thought the old advice was it's bad for burr formation? What is the change in observed result that this is ok?
Binder filling the throughs. This I never thought before. Gotta be watchful now ...

Glad all these are in one thread, I can refer back often. :thumbup:

Edit to add question & sorry to derail the thread:
The 400/800 or mine 400/1000 are used with water. How do I know it's SiC or AlumOx? I thought it's AlumOx, but no way I can differentiate. Tips please ....

 

[HeavyHanded]

Chris, for burr removal I switch to leading edge.

I learned this on:
- soft waterstones
- wet/dry, lapping films
- diamond plates

Very different but maybe not - it limits abrasive displacement as you work. Anything that limits gouging and mineral displacement on soft stone, adds life to wet/dry will also add life to a diamond plate.

 

[David Martin]

I have wondered about this too.
Plus, I as well only use my diamond stones in a edge trailing format as I think this saves the diamond surface. But to the detriment of creating a more convex edge. Yes, edge
leading on aluminum oxide and SiC stones to remove the burr, using light pressure. DM

 

[Steel_Drake]

I'll give you guys three guesses on what I'm about to say, though you probably won't need them.

There is an obvious tool choice for this application that is being overlooked. Sigma Power Select II waterstones are made from silicon carbide with very little binder, and should have no trouble cutting any steel regardless of hardness or wear resistance.

Exhibit A:

[video=youtube;Tsj1U2bx-L8]http://www.youtube.com/watch?v=Tsj1U2bx-L8[/video]

Considering I managed to successfully apex a ceramic knife on an SPS-II 1000, I don't see why it would have trouble 10v.

 

[BluntCut MetalWorks]

I need to reassure myself (to erase a inkling bugger of doubt) about stropping with 0.25um diamond abrasive. Rounded & wire edge are often the negative consequences of stropping. My setup would exhibits both bads if so.

CruforgeV, 0.010" BET, Sharpened at 10 dps with 1K waterstone then stropped against 0.25um diamond powder at 10dps angle with 50 strokes per side. Strop backing is a non-flex but not hard surface (can easily dent with finger nail)

400x

1000x

Result looks nifty clean and this very keen apex tested to be quite durable (another confirmation of no wire-edge). 400x shows what look like some rounding however I suspect light got scattered, so 1000x shows area near apex at higher accuracy.

 

[HeavyHanded]

In my experience, wire edge from stropping is really just the burr showing up/being polished. Rounding is always a danger, burring IME only from very hard backing and/or abrasives larger than about 15 micron. Developing a wire on an edge that is slightly rounded or dulled is difficult unless stropping right on hardwood.

Other factor is if the abrasive gets swamped by swarf and is a hard backing you might see some burring. Fresh abrasive or some mobility to the compound layer should eliminate even this.

YMMV

I have to stick to my guns re abrasive types etc. Assuming about 10% average of abrasive is proud of its binder in a plate or vitreous bond (maybe a bit more on a plate but not by much), by the time you get to 600-800 grit ANSI the available abrasive is butting heads with comparable sized carbides. In the case of Vanadium and Tungsten, severely impeding the clean abrasive process.

At this level one really needs to switch to diamond or CbN for further refinement or risk burnishing or excavating the carbides. The question I have and am unable to address - if larger abrasives that excavate carbides and steel per pass are fracturing the carbides into a sharp presentation. How else to get a sharp edge when the carbides are > sub micron?

 

[BluntCut MetalWorks]

HH - good ending question and of course insight... LOL - seem that we have been here before with these stuff

btw - I can generate a large visible wire-edge when strop with 0.25um diamond on hard felt or leather. After numerous 'dohs', I threw away those make-shift strops.