A sharpening thread of my very own (Japanese Natural Stones).

[Stanley Covington]

Deformation on this scale typically hardens metals if anything (strain hardening), though that's not really applicable to super-hard tool steels.

The phenomenon you describe is theoretically possible under very rapid deformation, but there's a minor conservation-of-energy problem for hand sharpening. I don't think that a human could add energy fast enough by moving their arms back and forth to achieve those sorts of temperatures even locally, keeping in mind that the whole process is liquid (water, oil) cooled and that metals are very conductive.

Can you point me to any direct evidence of this happening during hand sharpening? Again, I know it can happen with very large power inputs, but that's not what we're talking about here.

Patrick:

You bring up some very astute points.

I should clarify what I mean when talk about burnishing being a bad thing in some cases.

The first point I should clarify is that the same thing can happen on almost any stone, but I think it happens easiest on novaculite stones because their pores tend to clog, especially when the stone is used dry, or when the water dries, or lubricating properties of the oil decrease. You know what I mean: "The glaze."

I agree that burnishing is unlikely to occur if the stone is kept lubricated.

Second point. You are right about the pressure. But pressure is a relative thing, so if someone applies a lot of speed and pressure to a blade on a dry stone, and glaze develops, the pressure applied to a very small area on top of a ridge of glaze (as seen from a bacteria's eye view) can, in my opinion, create enough heat to soften the steel locally. I believe this occurs most easily at the extreme points on the cutting edge where there is not much backing metal to act as a heat sink.

If we scale the phenomenon up a bit, perhaps it will make more sense. Have you ever seen a large slab of concrete being dragged over another slab of concrete as it is suspended by a crane? The contact of course is not even, and where the two slabs meet, gouges are cut into both slabs, and dust and smoke flies. The slabs themself never heat up, but the aggregate gouged out of their surfaces is steaming and very hot.

But as I said before, I have no hard evidence.

Regards,

Stan

[Stanley Covington]

Not all of us are as inexperienced with Arkansas stones as Stan. His arm chair theories are incompatible with real world experience.

Warren:

My armchair theory is just as valid as your armchair theory. Mine has a couple of engineering degrees and real-world experience in structural design padding it out when the discussion involves materials science.

I for one am sincerely eager to learn from your real world experience, Warren. Please take the time and make the effort to add something to the discussion instead of just throwing cold water on everything.

Thank you in advance.

Stan

[Kees Heiden]

This discussion will probably remain armchair theorising for us. It's just not doable for us to really know what happens down there at the atomic level. Weird things can and do happen on such a small scale.

I'm glad I have now a better idea about your former comment on burnishing. Treating my Arkansas stone withe reasonable care, using oil and wiping it clean after work, I don't see it glazing up too soon. But because I don't dress the stone or scrub it with diamond plates or whatever, and because these stones don't release grit easilly, I am sure the grit particles will be rather rounded. So some plastic deformation is inevitable. By the way, sharp grit works with a mixed action of cutting and deformation too. Those grit particles are not like rows of neat chisel edges lined up at a 45 degree cutting angel next to each other. They are tumbled about and scrape and cut and plow all at the same time. Sharp grit certainly works a lot quicker then rounded grit of course, but tends to leave deeper trenches at the same grit rating.

Glazing btw is in large part a matter of a stone filled up with steel swarf. So the action of the grit particles is seriously hampered by all that swarf clogging up the pores of the stone and the steel will heat up much quicker.

It was fun to watch Brian's approach to sharpening Japanese chisels and the care he puts in not just creating a very sharp edge but also into the appearance of the bevel. I am afraid he would turn away aghast from my Japanese chisels. They look awfull. I treat them like western chisels, do the primary on a fine India, I might polish that up a bit with a Washita and then do a small secundairy on the translucent Arkansas, followed by a stropping on a well worn in Autosol treated strop. If I nick a corner of a blade accidentally, I am not afraid to use a dry grinder to bring it back in shape . Nonetheless I am very happy with these chisels. They are very well made, I like the laminated construction and they sure do get very sharp very easilly, and keep that edge for a good while.

[Brian Holcombe]

Theory or otherwise it is a great discussion and certainly interesting to think about.

Kees, thanks for the comment, I may well turn aghast as you say Be forewarned, if you decide to create a nice kasumi finish on those chisels it will be hard to part with in future sharpening sessions.

[Warren Mickley]

I watched Brian's video a second time and thought I would make a few comments.

I give Brian high marks for his technique and for his discernment. I think these things are actually more important than a workers equipment; without these the finest stones are not much use. In talking about technique we need to look at not only the manner in which something is done, but the quality of execution. Brian's motions are all smooth, very clean and crisp, without clumsiness or extra little quirks. Unlike many others, when he says he hones at 30 degrees it is apparent that he is actually doing so.

By discernment I mean having a feeling for what is going on with the stone. As examples: knowing when the stone is cutting well, being able to feel when the stone has done it job of making a nice edge or removing roughness from the previous stone, knowing when the edge needs work, knowing which stone is appropriate and the like. Rather than just going through the motions and following a recipe, Brian seems fully involved with all his senses.

One thing I was tickled to see was that Brian let the plane iron overhang the edge on both sides. This is something I have preached on forums for about a decade without seeing many pick up on it. This enables one to manage the wear on the stone. It takes skill to balance the iron like this and to take the rapid strokes that Brian takes. Some encourage beginners to keep everything locked and sway the whole body. Brian's motion is more complicated, but so smooth it looks simple. One thing I wondered about was the short stokes, perhaps only one third the length of the stone. I use rapid strokes like Brian, but nearly the full length of the stone.

Brian, you ground the iron at a shallow angle and only honed a small portion of the bevel; I wondered if this was usual for you or if some tools were full flat bevel.

[Brian Holcombe]

Thanks Warren! I appreciate the comments. I actually overhang the stone after reading one of your posts recommending the technique some years back, I find it very easy to create and maintain a light camber using that method.

All of my Japanese tools are full bevel but my western tools are a mix.

[Patrick Chase]

I'm glad I have now a better idea about your former comment on burnishing. Treating my Arkansas stone withe reasonable care, using oil and wiping it clean after work, I don't see it glazing up too soon. But because I don't dress the stone or scrub it with diamond plates or whatever, and because these stones don't release grit easilly, I am sure the grit particles will be rather rounded. So some plastic deformation is inevitable. By the way, sharp grit works with a mixed action of cutting and deformation too.

Technically speaking, cutting *is* deformation.

You can't cleave a material without locally exceeding its ultimate tensile strength, and to do that you must have first exceeded the yield strength. In an extremely brittle material those values are very close to each other and so not much plastic deformation happens before fracture, but for the sorts of metals we're talking about here there's all sorts of deformation going on.

The key figure of merit is the amount of power dissipated via plastic deformation per unit volume material removed. In general sharper/harder abrasives do better in that respect than dull ones. If this sounds familiar, that's because it's *exactly* the reason why friable AlOx grinding wheels are "cooler running" than ones with hard binders, and why CBN and diamond are much cooler still.

Two offhand remarks:

1. Earlier in the thread Stanley brought up scratch geometry/sharpness and argued that SiOx is better because it leaves smoother/rounder scratches. Unfortunately this is a case where you can't have your cake and eat it too. JNats leave rounded-off scratches precisely because the abrasive isn't particularly sharp and isn't cleaving the metal cleanly and there's lots of plastic deformation happening.

2. On a related note, if heating via plastic deformation were really an issue for hand honing, then natural waterstones would be a far from ideal way to address it. If you're really worried about plastic deformation then you want the sharpest, cleanest-cutting abrasives possible, and that means you should be using diamonds. IMO it isn't really an issue, though, and therefore isn't a valid reason to use diamonds for hand-honing.

On a more practical point, my own experiences dovetail with Warren's last comment: What you use matters less than how you use it (provided the steel and the medium aren't glaringly mismatched - you're never going to get good results with CPM-10V on any SiOx stone, for example). There are certainly speed/convenience/cost tradeoffs between media of course.

[Phil Mueller]

Brian, somehow I've missed your sharpening video (per Warren's post) and can't find it on your blog or within this thread. Can you repost, or link me in the right direction?
Thanks!

[Brian Holcombe]

Certainly, here is the video;



I work the try plane iron in this video, I may do another with Japanese tools.

[Patrick Chase]

Those grit particles are not like rows of neat chisel edges lined up at a 45 degree cutting angel next to each other.

What, you don't hone exclusively using Trizact?

Or better yet *diamond* Trizact, at only $230 or so for a 1x60 belt.

[Stanley Covington]

Two offhand remarks:

1. Earlier in the thread Stanley brought up scratch geometry/sharpness and argued that SiOx is better because it leaves smoother/rounder scratches. Unfortunately this is a case where you can't have your cake and eat it too. JNats leave rounded-off scratches precisely because the abrasive isn't particularly sharp and isn't cleaving the metal cleanly and there's lots of plastic deformation happening.

I think you misunderstood my post. Synthetic stones cut steel faster because of their abrasive particle's very pointed geometry and the particle's relative hardness. I like this and think it is superior because it saves time, and because synthetic stones cost less. I did not write that the particles have rounded geometry.

Natural stones of the sedimentary type mined in Japan ( but not just Japanese sources) are typically made of more friable particles with rounder geometry. They clearly cut and polish less aggressively, but the nature of the scratches they produce results in more dispersed light refraction and a consequently different appearance to the steel in the case of the higher quality finishing stones and stone veneers used for polishing swords. This is well documented and standard procedure in the sword polishing industry. Of course, it applies to tool blades to some degree. I thought this point too was very clearly presented in my previous posts. Curious...

I am not "having my cake and eating too." I have repeatedly mentioned the trade offs, but since careful reading is a rare skill at SC, I will state it very clearly, again: Compared to synthetic stones, high- quality natural Japanese finishing stones are less efficient at wasting metal. They take more time to finish a blade. They cost a lot more. But in my opinion, the results are more attractive and the cutting edge retains sharpness a little longer. I am not alone in this opinion, although those of you without practical experience using them may doubt me. That is your loss.

Please experiment for yourself with a high-quality stone and a high- quality blade and you will immediately understand.

[Mike Holbrook]

"It's just not doable for us to really know what happens down there at the atomic level. Weird things can and do happen on such a small scale."

Except everything apparently happens at the sub atomic level chemically. Chemistry, sometimes called the central science because it bridges other natural sciences including; physics, geology and biology, tries to define the composition, structure, properties and change of matter.

If we are to believe physicists the relationship between matter and energy at the quantum level gets a "little" complicated. The further we look into sub atomic particles the more space we find without actually finding "solid" matter. Energy seems to be the most "solid" sub atomic component. Maybe we will compose a mathematical formula, if one exists, that will define exactly what happens at the sub atomic level, maybe not. The point being that until we do the jury is still out and it is all theory. Unless we come up with "THE" formula on this forum everyones theories, taken from our own experiences, have value.

No one has "the" one correct answer with all perfectly correct variables, calculated for all conceivable conditions, so why waste our time arguing about it?

[Stewie Simpson]

Brian; after watching your video I took note of the additional effort required by you to work your closely set double iron tri plane; the following blog entry by Richard Maguire should be of some interest. http://www.theenglishwoodworker.com/cap-iron-fatigue/

I had a bit of a chuckle when I read Richards subtle response to Kees objection.

Kees van der Heiden March 3rd, 2016 Sorry, you are wrong Richard!
The trick is to set the capiron at an appropriate distance. Too close and planing becomes real hard work. Too far and it isn’t helpfull.
Especially in the try-plane fase of dressing a board, the capiron is very valuable. Sure, don’t set it too close, but set it close it enough that it prevents disasters, deep tearout that takes ages to remove and makes you go beyond layout lines. On a troublesome board this won’t give you a blemish free surface, that’s the smoothers job, but it sure beats deep tearout.
A capiron beveled to no more then 45 degrees, set at an appropriate distance from the edge is really not so bad in the aspects you mention. Extra resistance makes you feel that the capiron does its job. If you really want to know what hard work is, try a plane with a high cutting angle.
Reply

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  Richard Maguire March 3rd, 2016 Hmm… so ‘wrong’, yet you agree. A cap iron that’s doing something adds resistance.
  Not everyone’s aware of this and it’s an essential mechanic to understand.

[Brian Holcombe]

Hi Stewie,

The work I typically do with the Try plane is to true a panel or board prior to finish planing. Tear out at that juncture causes a substaintial increase in the time spend on the finish plane. So it makes the planing easier but the work harder.

I realize that I was jointing the edge of a test board, which is also work I do with the try plane.

It's funny that you bring that up, I was just reading that article this morning.

[Stewie Simpson]

Brian; you have probably viewed Richard Maguire's previous video on his blog site; http://www.theenglishwoodworker.com/...ear-out-video/

Within the comments section; Richard offers some clear insight on his approach to the use of cap irons.

Richard May 11th, 2015

Warren; don’t worry, I left the concerns of tear out behind with puberty. As David said, this is a great topic worth further discussion, but is beyond the scope of this video and this post. I aim for clarity on subjects for my audience so try to cover one point at a time, but I have mentioned previously that I don’t simply class a plane by it’s length but how I’ve chosen to set it up for use. 90% of my work is finished off the try which is set up closely to my smoother (I don’t do any of the wispy, thin gravity defying shavings).

If I’m hogging off material however then I won’t concern myself with the cap iron, I don’t have problems with tear out since I’ll read the wood, make judgement and alter my approach on the fly, but that’s a whole other subject. I’ll not just judge every piece of wood as being the same, I’m working it by hand so I can respond as a human.

When I look for the positive point in what you’ve written I do find that we’re almost on the same page… almost.