Thread: Reasons I feel hones have to be sedimentary

Ah, just a few technical corrections but mostly just additional info. I was a geology major so I have to make use of all that accumulated petrological trivia somehow.

I see. Lol, I'm a mechanical engineering major so I deal a lot with structures and stresses. Hence the motivation behind this thread- I am trying to reverse Engineer rocks lol. It's bad being an engineer. I bet a lot of people can agree with me on this, but once you start physics, suddenly you look at everything differently. After you take statics and dynamics, suddenly things like a swing begin to remind you of oscillations, differential equations and forcing functions... its bad. I distinctly remember a time when I flew after we did a case study on airplane rivets in class. I ended up describing to the woman next to me about micro stresses on the rivets whihc lead ot micro cracks which in old planes can unzip and tear the fuselage (a la Hawaiian air a few years back, or that one plane just recently) needless to say I thought it was interesting and she felt sick the whole flight.

ANYWAYS, back on topic, so yes I have some inaccuracies. Some of this inaccuracy comes from the fact that my info is second hand from my grandfather who is a geologist/mining and drilling engineer, the rest is typically born of the fact that I am tryign to find simple analogies to explain my points, but very rarely are analogies perfectly accurate, and even more rarely is a simplification accurate.

Ha ha, yes indeed! I was originally a physics and chemistry major but slept through too many calculus classes and had loved rocks since childhood so switched to geology and computer science (don't ask me how I managed to minor in math while sleeping through calc.) But, yes I hear you. I see a 2 foot diameter steel shaft driving a turbine at the local power plant, and in my mind I see it flopping like a wet noodle as it spins. That is why when I think of sharpening stones, I think of the steel as being modelling clay (sometimes with small objects blended in if I also need to model carbide grains etc.) and the stone as being like clay sculpting tools (those little wooden rakes and spatulas) to model various grit sizes and burnishing tools.

Silicon carbide is harder to model... it has flatish, sharp, elongate crystals that can dig deeply into steel but steel has a high tensile strength and can easily snap off the carbide grains embeded in it (which is why SiC is not recommended for grinding ferrous materials).

Where do you classify sintered stones... made of grit particles that are heated so their surfaces partially melt and stick to each other.... like Novaculite, the cement is exactly the same material as the abrasive.

Hmmm... now we're getting into the realm of what is stronger... EM forces or physical force lol.

First a few definitions- not necessarily THE definition, but explanations of how I am going to write things:
Network/lattice solid: Covalently bonded lattice solid- such as diamond (carbon lattice) or silica (Silicone/Oxygen lattice), since it is a covalent bond this is an INTRA molecular force, and will refer to the whole lattice as a "solid" or single molecule (not technically correct, but otherwise hard to do)
Sintered bond: I am going to assume that the sintered bonds are INTER molecular forces, and occur between large lattices/crystals/solids/molecules
Metallic bond: Obviously these get tricky, and just as a clarification these are INTRA molecular bonds- therefore also forming "solids" or "single molecules" (metallic version of lattice, sort of...) complete with mobile electrons etc.

Now, I would classify sintered hones as "solid" if the sinter bonds are much stronger than the metallic bonds in the blade, and "bonded" hones if they are weaker.

Here is where I feel it gets very very complicated lol. Honing is a physical abrassion (at least the way we do it). One now has to determine the force of impact between the honing compound in question with the steel's edge. This is obviously a physical force. If this force exceeds the strength of the sintered bond, but not the metallic bond, then you will have a hone that is simply worn away, doing little/nothing to the steel. However, if the molecules/lattices are stronger than steel this CAN form an abrassive slurry(case 1) If the force exceeds the metallic bond but not the sintered bond, then you have a hone that will cut steel but not break away at all/very little. (case 2) That's simple to follow. I think the issue comes when the tolerance is close enough the the physical force could break both bonds, which would mean both the hone and the edge break down, which would create a slurrying hone, correct? The steel is being sharpened, yet also particles being released into a slurry. (case 3) This I feel would be ideal- but would require a very lucky/well planned tolerance.

Now what would the grit of such hones be? In case 1, the hone is useless by itself, but could make a good slurry stone. In case 2, it would depend on the texture (as I argue it would with solid hones), and in case 3 we have a very efficient hone that behaves much like coticule I would think- cuts using "embedded" particles, but could also use a slurry. In case 3, the grit would depend on the molecules/lattices being released. If they are a consistent size, then it would be a consistent grit. If the strength of the covalent lattice bonds is less than that of the metallic bond of steel (case 3a), the particles would be useless though as they would break down. If they were harder than steel you would have a good slurry (case 3b)

Now I'm not good with sintering stuff, but I think in the end, if you managed to get say, ruby powder, at a very fine, consistent size, and sintered it weaker than the edge of a razor's edge holding capacity (metallic bonds), then you would probably have a very good bonded abrasive hone. If you say, sintered it almost to a solid, synthetic ruby, I feel one would have to texture the surface (much like one textures the surface of a steel file)

Of course... this eliminated the MASSIVE calculations and skipped to the results lol. One would have to determine bond strengths, stress/strain in the steel and hone structures, and inter/intra molecular forces. Once one does all that it would be relatively easy to figure out what breaks first and apply that.

I'm trying to think of a macroscopic example but I cant lol. EMF's trump physicals at tiny sizes (this is what makes atoms work), physicals trump EMF's at large sizes, (this is what makes solar systems work) but I feel we're at the weird place where they start to intersect...

Originally Posted by khaos

Of course... this eliminated the MASSIVE calculations and skipped to the results lol. One would have to determine bond strengths, stress/strain in the steel and hone structures, and inter/intra molecular forces. Once one does all that it would be relatively easy to figure out what breaks first and apply that.

I'm trying to think of a macroscopic example but I cant lol. EMF's trump physicals at tiny sizes (this is what makes atoms work), physicals trump EMF's at large sizes, (this is what makes solar systems work) but I feel we're at the weird place where they start to intersect...

I just do the X stroke with the heel leading slightly.

Originally Posted by JimmyHAD

I just do the X stroke with the heel leading slightly.

Lol. Following that advice someone might be stuck on the gypsum 50k for a very long time....

GAAHHH, I HATE when I type up a whole page and then loose it! AAAAGGGHHHH

So, you get the monosyllabic summary.

Case 1... jade or sintered hones will be mechanically abraded down to a mean surface roughness that relates to its internal grain size (thus two sintered ruby stones or ceramic crock sticks may insist on behaving differently because they have different internal grain sizes). Once it is broken in like that, it will be at its optimum. a dressing stick or diamond plate will need to be used periodically to expose fresh grain after this type of hone begins to loose its cutting ability.

Glass hones are amorphous and have no internal grain so they simply need to be replaced, refrosted, resandblasted or re-etched to their desired roughness (I suppose if someone grew a huge ruby crystal, or stole the rod out of a big ruby laser, they could use a diamond and make a file out of it, in which case it would act like a glass file).

Case 3 is how waterstones generally work... the binder is intended to give way as fast as the grit dulls. With synthetics we get a grit number and it we ask around we may learn a stone's relative hardness (equivalent to the "grade" of an industrial grindstone rather than the moh's hardness of the abrasive), but we still don't know how a stone will work 'til we try it with a particular steel (I've got a lot of stones... here are a few of them:


and each steel seems to have its favorite stones)

I've seen photomicrographs of tennen toishi (natural Japanese whetstones) and the grit appeared to be made of flattish flakes. I have a feeling that these tend to shave off the high spots on steel rather than plow furrows in it like hard football shaped crystals of synthetic abrasive... This may have something to do with sword polishers only using natural stones saying that they reveal the activity in the steel rather than plowing it under and obscuring it like a synthetic stones do.

On a similar note, here is a photo of some 3M silicon carbide microfinishing film:



Notice the flattish blade like fragments? Well, even though SiC is not recommended for grinding ferrous materials, I suppose you could use it for low pressure hand polishing. Wonder if it would leave a different surface finish than Al2O3 or diamond???


Some of the artificial stones, like the Kitayama 8000, mix in some natural stone poweder and the slurry is supposed to crush down to closer to 12,000 grit so with a little care, it can produce a finer finish. My natural aoto is like that... I'd estimate it to be about 1.5k if I use it under running water, but if I let the slurry accumulate, it acts more like 3k or more.

I will say I noticed this "crushing" thing on my awase-toishi- after lapping its rougher than after many uses without lapping. So now I don't really lap it.

As to what you said about case 1- I feel that would be more accurately put with case 2- but I totally agree with you. If it has some grain structure to it, or a way to controllably texture the surface, it can work, but is not optimum. How many sintered hones will all the grains be within a certain tolerance, unless they are manufactured? And if they were cost effective, surely they would be manufactured more often than the case 3 hones? I think we are largely in agreement though.

I have also noticed "finishers that just match..." but that's a whole other story. I once suspected it has something to do with the type of steel matching the crystalline structure of the abrasives in such a way that they can cancel to a "flat/straight" edge. This thread isn't totally accurate or fully thought through but you might like it: http://straightrazorpalace.com/basic...r-musings.html

Originally Posted by khaos

I will say I noticed this "crushing" thing on my awase-toishi- after lapping its rougher than after many uses without lapping. So now I don't really lap it.

I was talking about working the mud on a stone... the mud or slurry will become finer as honing progresses... I.e. you start honing on an 8K Kitayama stone, work up a slurry and then polish on the mud, the particles in the mud will break down and give you a 12k finish... though perhaps people don't build up a slurry for razor honing?

How many sintered hones will all the grains be within a certain tolerance, unless they are manufactured? And if they were cost effective, surely they would be manufactured more often than the case 3 hones? I think we are largely in agreement though.

Oh, nature can produce some pretty homogenious textures via sedimentation or partial crystalization. I mean they might vary quite a bit over an area of several acres, but be pretty much the same over the space of a few cm or meters. Oh, sintered hones are... nearly every western sharpening stone from a hardware store (common oil stone) is a hard sintered SiC or Al2O3 block. Crock sticks would also fall into that category as do machinist's ruby stones.

I have also noticed "finishers that just match..." but that's a whole other story. I once suspected it has something to do with the type of steel matching the crystalline structure of the abrasives in such a way that they can cancel to a "flat/straight" edge. This thread isn't totally accurate or fully thought through but you might like it: http://straightrazorpalace.com/basic...r-musings.html

Interesting. Not sure where fourier analysis would go with this... even harmonics produce triangle waves and odd harmonics produce square waves... doubling the grit halves the particle diameter, and the grooves left by the particles would probably be D wide and 1/2 D deep unless the abrasive is used with too light a pressure to sink it in very far (more likely with round crystals like garnets would produce shallower scratches due to the ~120 degree angles on the vertices requiring more pressure to sink them halfway into a steel surface than sharp angular xtals like diamond).

Since, unlike knives, razors are mainly stropped on the surface of a hone using the weight of the razor, it is likely that even sharp abrasives probably do not embed much beyond the tips (though particle density per unit area would be lower so each cyrstal would ge more pressure and tend to sink in more than a smaller grit would... up to a point anyway), and at that point Utopian's idea of grinding off the tips of the peaks begins to make more sense (probably also if there is a large a skip in grit size). The pyramid honing probably also helps dislodge bits of burr or work/flow fatigued steel from the edge.

Unlike SEMs, depth of field in a light microscope is rediculously shallow, but here is a pic I did of the edge of a fresh Xacto blade...


pretty wavy there. I'm more into chip carving knives and wood and I've never done a microscopic analysis of the dynamics of various tooth shapes on the sawing, or slicing, of hair but people complain that diamond makes a razor too sharp and grabby, so maybe it makes a very fine but toothy edge that acts like a saw, while coticule makes a more gently curved scallops that are not quite so agressive at biting into hairs and thus don't pull as much?

A lot of variables to look at there, though maybe getting out some clay and experimenting with some cardboard rakes could simplify things (did you see the neat photos of sidewalk chalk another user posted?... they look a lot like what I see under my microscope so maybe chalk and various rough surfaces would also make a good model!)