Thread: Reasons I feel hones have to be sedimentary

Originally Posted by yuzuha

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!)

For a long time now my large-scale simulation of a razor edge has been those big pink rubber erasers and files/rasps etc. Among other things they seem to model the formation of burrs pretty well.

With the fourier thing I think people got carried away with the accoustics- i didn't mean vibration at all, I just used it as an example of wave combinations. What I was thinking is the 2d profile f(x,y) can be broken into tiny pieces F(x)dy- very thin slices that look like mountain ranges (that can be approximated with a fourier series). Then as the blade edge passes over these, each thin slice gouges the blade. If the gouges can approximate a straight line, then you have a good hone- So I absolutely agree with your diamonds vs. garnets argument. In theory if one had a "perfect" hone these thin slices (dy) could each have a low frequency/large period (rough grit) and STILL cancel out. However, its more likely that as you add higher and higher frequencies you get closer and closer to a straight edge approximation. So in the series (Sigma)cosax+sinbx....a 1k hone could cover a=b=1,2,3,4, a 4k hone could cover 5,6,7,8, an 8k could cover 9,10,11,12, and so on. With a good approximation, fewer frequencies are needed (round garnets more closely approximate a straight line than angular diamonds). So in theory, an 8k garnet (coticule) cut would be a better smooth approximation than an 8k diamond cut- so we may not be getting into high enough grits with the diamonds to accurate approximate a straight line.

This is why I did not go far in physics. One question, if you physics kooks know the momentum of your razor(mv) could you be certain it's location?
M

Yes, I was thinking of profile slices in the x,y plane but the then frequency spectra in the y,z plane, but now that you mention it, an FFT of a photo of a waterstone looks very interesting... pretty much a dot with a cross and a cloud of haze around the dot that diminishes towards the edges of the frame. One of these weeks when I'm on vacation and get snowed in, I'll have to fire up the microscope camera and photograph various stones and compare their FFT's, maybe tinker with them and then invert them and see what comes out.

Also wondering about randomizing grit sizes in the pyramid... say you pyramid 4k then 8k then drop back to 6k and jump to 12k to sort of throw in some odd harmonics there.... alternating between grits in the sequence x*2^n and then do a round alternating between grits in the sequence 1.5x*2^n as the particle sizes would be inversely proportional.

Think that cancelling at low frequency may be what happens to an extent with motorized grinding wheels since power wheels seem to produce a finish that is finer than you'd guess from the grit size (your thin slices are striking tangentally to the radius of the wheel so they do not interfere with each other in the z axis as they would with a flat grinding surface), or maybe that is just an effect from pressure and stock feed rate?

Originally Posted by Kingfish

This is why I did not go far in physics. One question, if you physics kooks know the momentum of your razor(mv) could you be certain it's location?
M

Not with any precision beyond that it is somewhere on the original p-brane

Originally Posted by Kingfish

This is why I did not go far in physics. One question, if you physics kooks know the momentum of your razor(mv) could you be certain it's location?
M

Since its possible that all masses travel in waves (bigger masses in REALLY small waves...) we can't be CERTAIN lol. We can get accurate enough for practical purposes though. :P

I would personally think that to "cancel" your frequencies to a "straight" edge, one would either need a high level of randomization (with no harmonics obviously) or a very high level of design/planning. I'm not so sure that randomizing grit would help so much as randomizing the individual "slices" of the hones. Though I doubt it could hurt. I have only a handful of razors that I am willing to dull and sharpen excessively, so if anyone else wants to try this, go ahead lol.

Also on the note of grind wheels, your theory holds some weight. I do not know enough about them first hand but I would guess that its a product of higher efficiency. On a 8 inch hone, going really really fast, I saw someone crank out about 100 laps. Thats only 1600 inches. On a 4 inch diameter wheel, that would only take 125ish rotations. For something that spins on the order of several hundred RPM, thats a piece of cake. So... one can get the same grind in less time and therefore can use less pressure, so there are tons more scratches and not as deep. Keep in mind, the grind wheel will always spin fast, its a machine. I know for a fact that most people cannot do 100 laps a minute on a stone. Thats my thought anyway.

Just wondering if anyone mentioned changing the direction of the slices to form a plane.

What do you mean?

Imagine a plane, then cute the grooves from a sharpening stone forming what would look like channels on it. Then flip it 90 degrees and do the same you should end up with something that looks like peaks on most of the blade but the edge itself being one line should be smoother than if just cutting on one direction.