Est. 1998 — 27 years of woodworking knowledge
Ahh, got it...
John in New Mexico
>the rock-earth analogy is what I missed. In all honesty I can't really fault the use of "entropy" as 99% of the western world seems to use the word that way. Its been going on long enough that all of us semantics obsessed scientific types probably ought to accept it ;).
I prefer natural sharpening stones myself, though mine all are from Arkansas.
John
Re: Ahh, got it...
Pam Niedermayer - Austin, TX
>We probably have Nova to thank for that. :) I felt much the same way when computer science/software development terms hit popular use.
An Arkansas was the first stone I ever used, about 30 years ago; but it was such slow going that I swore off them. I understand now that I may have had an inferior stone.
Pam
Re: Matte vs. Mirror Finish
paul womack
> In order for a stone to effectively sharpen at all, the distribution of particle sizes has to be pretty narrow. It only takes a few outliers from the previous stones grit range and you'll never remove all of the coarser scratches (since you'll constantly generate new ones).
That appears unarguable - which leaves a mystery, assuming that the reports of good sharpening performance with (assumed ;-) non uniform natural stones are validated.
BugBear
Possible answer to paradox
wilbur
>The paradox of uniform vs. random particle sizes in a natural sharpening stone and its performance can be easily resolved. It is clear that man made stones can be made more uniform than natural stones. However, natural stones have random particle size within a fairly narrow range.
The layers of rock that provide natural sharpening stones probably are sedimentary in nature, judging from their characteristics. These layers were probably deposited by natural currents of some sort. The fact that these sharpening stones come from specific layers indicates that the particle size is relatively uniform.
Think of the last time you were walking on a beach as the tide pulls out. If you look closely at the waterline, you'll see that the grains of sand have some organization by size. This is because sand grains of different sizes will be carried different distances by the same current of water. Multiply this process over the time needed to create a layer of sedimentary stone, and you'll wind up with areas of relatively uniform particle size. Pick the right area, and you'll have a sharpening stone mine.
In Toshio Odate's book on Japanese tools, there are some micrographs of sharpening stones and blades sharpened by them that clearly illustrates this point.
It may be that the current crop of man made stones have particles so uniform in size that the performance of these stones will differ from natural stones of the same nominal grit size. Whether this translates into improved sharpening performance is actually a different question. Remember, the metal particles that make up the blade are also going to have some randomness in size as well.
Re: Possible answer to paradox
paul womack
>However, natural stones have random particle size within a fairly narrow range.
If the range is narrow enough - yeah, the question does not arise.
I was intuiting (from this thread) that the size range in natural stones was significantly higher than in man made stones.
BugBear
A couple more variables...
John in New Mexico
>though I won't go so far as to speculate how they affect sharpening. First, Wilbur is correct that natural stones are sedimentary in nature, and almost certainly grainular in texture, rather than a precipitate like limestone (too soft to sharpen steel). The mistaken assumption in my opinion is that these stones would be as uniform in compostion as a man made abrasive stone. I would guess that the variability of minerals in natural stones is of more relevance than the uniformity or lack of it in particle size. The other variable, which is actually related, is that natural stones of this kind would likely be more friable than a man made one, also due to its heterogenous mineral composition. This is a bit analogous to diamond crushing less easily than SiC, and thus behaving differently as an abrasive material. I would suspect that the friability of the stone is what produces the matte effect, though I couldn't tell you why it is also sharper. Perhaps the availability of fresh abrasive cuts more efficiently and dubs the edge less.
John
Re: A couple more variables...
Pam Niedermayer - Austin, TX
>It's analagous to files and rasps. The handcut, stitched versions from Auriou leave a smoother surface than the machine made, regular ones from other vendors.
Pam
Oops, should be "analogous"
Pam Niedermayer - Austin, TX
>
Re: A couple more variables...
paul womack
>It's analagous to files and rasps. The handcut, stitched versions from Auriou leave a smoother surface than the machine made, regular ones from other vendors.
This would only be true if the abrasive particles in the man-made stones were in some kind of regular tessalation, which I don't think is the case.
BugBear
Re: A couple more variables...
paul womack
>I thought the observation that we're trying to explain is that the natural stones ae leaving a visibly ROUGHER surface (i.e. not a mirror) and yet have (according to some claims) a sharper edge.
The analogy with a random cut auriou leaving a smoother surface (even if deemed a valid analogy, see other post) would appear to argue that the natural stone would leave a smoother surface, contradicting the observation.
BugBear
Re: Matte vs. Mirror Finish
paul womack
>Again these scratches on both bevel and back, when they meet at the edge, should make for a less sharp edge. Frank says that his observations contradict this.
I've reread the thread. Who's Frank?
BugBear
Re: A couple more variables...
Pam Niedermayer - Austin, TX
>Yeah, yeah, was just trying to illustrate how irregular tools can leave superior surfaces and do it faster; but I didn't think it through. Sorry.
Pam
Re: Matte vs. Mirror Finish
Denis Ch�nard, Orl�ans, Ont.
>Frank D in Montreal (higher up in the thread). Check here (hope tihs works):
http://www.woodcentral.com/cgi-bin/handtools.pl?noframes;read=100606
DC
Yet another thought...
John in New Mexico
>There are studies in mineral and gem polishing that some of the polishing action is chemical rather than physical. I wonder if there is something in the natural stones that contributes to an etching action in addition to the abrasion of the grains in the stone. Even if individual scratches were smaller overall than with a man made stone (read sharper edge), a chemical etch in addition could contribute the random light scattering that we see as a matte surface.
Has anyone thought of asking someone in the industry? Companies that make man made stones must have done some research into the natural ones while designing their products.
John
Re: Chemical polishing
Pam Niedermayer - Austin, TX
>Very interesting, John, where have you been all our lives?
Pam
I hate to admit it...
John in New Mexico
>I usually stay away from sharpening threads, being one of those quick and good enough type sharpeners. I lucked on to an interesting wrinkle this time though ;).
John
I hope others are reading this. Very interesting
Victor P
>
Re: Sharpening Japanese chisels - lifespan?
thomd
>I agree with the tap plane blades and everythign else pretty much you can tap, but sharpening is better. The reason we tap planes is to not thin the blade too much since it would affect the fit in the plane. With chisels it doesn't mater.
I maintain the main reason for the hollow is not to make initial sharpening/laping easier, which it does do, but in keeping with the practice of pollishing both sides of the chisel to and equal degree during sharpening, the hollow reduces the amount of work required by a huge factor. Throughout what writing we have about the tool culture one reads about large amounts of polishing. Odate recently wrote that he had throughout his life underpolished his tools. If you really put the work recomended into it, and I most certainly don't then one would know that there is an enoumous reduction in the maount of work required to polish a back that has been hollowed out.
You can pretty much use a Japanese chisel until the edge runs out up by the handle.
Re: Question, Dave
Dave Burnard
>You can try that, but I think, in general, that japanese or other hard steel chisels are probably too hard for it to work very well. My prediction would be that the edge of a hard chisel would chip at the level you are burnishing it. Recalll that's it's pretty difficult to raise much of a burr on a hard steel scraper with a burnisher
Burnishing also wouldn't move very much metal.
Worth a try - but I'll pass. ;)
Re: Sharpening Japanese chisels - lifespan?
Dave Burnard
>Yep, that the hollow is not just there for initial back flattening, but to make back flattening and sharpening easier throughout the life of the chisel.
That's why I choose to tap out my larger chisels from time to time - because I want to preserve as much of that advantage as long as I can. It may seem weird, but it's how I was taught to do it, and it works really well for me.
Ten minutes "moves" hollow 3 mm
david charlesworth
>If or when the edge reaches the hollow,
ten minutes work on an 800 grit stone will remove enough metal from the back to "move" the hollow back 3 or 4 mm.
I keep big pressure on the edge end and try to remove as little as possible from the shaft end, to maintain the hollow for the life of the chisel.
David Charlesworth
Re: Ten minutes "moves" hollow 3 mm
Pam Niedermayer - Austin, TX
>Thanks, David, you can grind away, at least until you reach bottom. But there are those of us who are, shall we say, more frugal with our cutting steel.
Also, for the moment, I prefer to treat the entire back at one time. I know, it's only the cutting edge that matters; but I don't feel all that comfortable modifying the geometry of the whole chisel. I've bought enough used western chisels to know how cumbersome and clumsy it can get when an edge is in a different plane from the rest of the back.
Now, you edge-only sharpeners can say that when it gets that far out of whack you can simply reflatten the back; but then you're taking off the same amount as you would have by just flattening the entire back.
Pam
Re: Ten minutes "moves" hollow 3 mm
paul womack
> but I don't feel all that comfortable modifying the geometry of the whole chisel.
Read David's post again - I think you misunderstood. This is not his famous "ruler trick", nor any variation of it.
BugBear
Re: Ten minutes "moves" hollow 3 mm
Pam Niedermayer - Austin, TX
>OK, looks like I misread it; but I'm still not sure why pressuring the edge end a lot won't produce the same result.
Pam
Re: Ten minutes "moves" hollow 3 mm
Frank D. in Montreal
>Hi Pam,
It's kind of like the difference between opening up a protractor and opening up a parallel ruler. If you apply more pressure near the edge, more metal will be taken off there, but if you're careful you can still keep the back flat (protractor; the pivot point is the heel of the blade). On the other hand if you apply pressure more evenly along the blade, you'll be taking off the same amount of metal at the toe and the heel, wearing it down evenly (and losing more of the hollow).