How sharp is sharp?

[RossJarvis]

That meeting actually took place just before the crusades started. They were not caused by religious differences but by an argument about whether the edge should be achieved freehand or with a jig.

:lol: :lol: :x :lol:

 

[Dangermouse]

So the consensus is then that there is no such thing as sharpness and it cant be measured if there was. :shock: (hammer) =D>

 

[Kalimna]

DM - Yes, we shall call it Schrodingers' Edge.

Adam

 

[WoodMangler]

http://www.catra.org/pages/products/kniveslevel1/st.htm

 

[RossJarvis]

That meeting actually took place just before the crusades started. They were not caused by religious differences but by an argument about whether the edge should be achieved freehand or with a jig.

Munich, 1938

"Look my dear chancellor, the man who does these things for me swears by an Eclipse guide, made in Sheffield by the way, just a few swipes across an oil-stone and you're good to go. You really must come to my place in the country to look at his beads and burl"

"Nein, nein, nein, mine kleine Etonion Dummkopf Nefille. It is wid ze wrists und ze shimmy, shammy, shimminess wid ze shoulders. I am haffink ze competition mit ze Krakow Carpenters next year, I challenge you und your Frenchie Friends ze year after. Mine gut freund Hirohito iss haffink ze competition ze year after zis mit der Honolulu Vood-Butcherss, he ist taking ze sacred stones of Kyoto und der water from Fuji. Zen you Anglo Saxonists vill know who der master carpenters are.

 

[Woodchips2]

http://www.catra.org/pages/products/kniveslevel1/st.htm

Sorted

Now shall I buy one of these or invest in a new oil stone (hammer)

Regards Keith

 

[ColeyS1]

If it slices through skin with out leaving a jagged torn mess, its pretty sharp

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[J_SAMa]

If there was a competition to assess sharpening methods how could you measure if your tools are sharper than any other? Would it come down to shaving the hairs on your arm or cutting a chamfer on a piece of very hard wood or is there a scientific way of measuring it?

Is a new blade for a craft knife as sharp as it gets or would it get sharper if you stropped it? I often strop craft knives when they get blunt because it is quicker than changing the blade but I don’t know if they are as sharp as a new blade!

Keith

Inspect the edge with a microscope and measure the radius of the edge.
However, even if an edge has 0 radius, it would be rounded off slightly as soon as it cuts something.

 

[woodbrains]

DM - Yes, we shall call it Schrodingers' Edge.

Adam

Hello,

Is the test shaving the hairs from a cat, then? :?

Mike

 

[Cottonwood]

Microtome blades are sharp, very sharp. They have to be as they are used to sliice tissue samples that were embedded in wax, for microscopic examination. If the blade isnt properly sharpened the cell structure gets ruined. The blades are honed on a machine that resembles a record player, with a big copper disc that revolves slowly in either driection. The blade is clamped onto a strong heavy arm and sets the blade down onto the copper disc, which is impregnated with diamond paste, at a pre determined angle. After a while the arm turns the blade right over so that the oother side of the cutting edge is on the copper plate, at that same angle. From what I remember, the resulting edge is about as sharp as a steel blade can be....theoretically, practically whatever.

 

[Phil Pascoe]

If it slices through skin with out leaving a jagged torn mess, its pretty sharp

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You should see the mess my sharp chainsaw makes!

 

[Fromey]

Microtome blades are sharp, very sharp....

They certainly are sharp, but part of the reason they can make such think sections is because the sample holder can be accurately moved to the blade in micrometer increments.

 

[Corneel]

http://www.catra.org/pages/products/kniveslevel1/st.htm

Wow, I nearly missed this one. A machine to test how sharp your tools are!

I propose we all buy one of these. That'll put somemuch needed substance in our sharpening discussions: "My edge is 0.01 N sharp!" :lol:

 

[marcus]

I propose we all buy one of these. That'll put somemuch needed substance in our sharpening discussions: "My edge is 0.01 N sharp!"

Yes, and then everyone can argue about whether the machine was properly calibrated... :?

 

[Kalimna]

May I propose, then, a new S.I. unit of sharpness - The Jacob? Something quite blunt (one of my chisels, say) would then be measured in kilojacobs, a well sharpened (by whatever method) could be centijacobs, and the microtome in nanojacobs? What say you all?

Jacob - I mean no offence whatsoever, purely in the spirit of a merry jape

Cheers,
Adam

 

[Cheshirechappie]

May I propose, then, a new S.I. unit of sharpness - The Jacob? Something quite blunt (one of my chisels, say) would then be measured in kilojacobs, a well sharpened (by whatever method) could be centijacobs, and the microtome in nanojacobs? What say you all?

Jacob - I mean no offence whatsoever, purely in the spirit of a merry jape

Cheers,
Adam

I like your thinking, but may I suggest that bluntness should be measured in Jacobs? Thus, sharpness should be the reciprocal of Jacobs - Jacobs to the power of -1, if you will.

We could define 1 Jacob as a chisel or plane iron freshly honed (freehand, of course - rounded bevel optional) on a medium olistone resembling a handleless spoon. A kilojacob would be the same chisel or plane iron before such treatment. The microtome would thus be about 1 microjacob.

David Charlesworth would be free to work in different units, of course.