How Sharp Is Sharp?

[sierraleather]

Aside from your blade being chipped or it drags so badly it won't cut butter,what is your definition of "sharp", and how do you test or determine what is sharp,thanks

[Ferg]

One of my Grandfathers died in 1940, I preface with this to set the time in my life. As farmers, all butchering and preperation of meat for the family was done by hand.Grandpa Newt had a set of butcher knives. The night before butchering he used a piece of native stone to whet the knives. Spit for lubricant, many strokes on that old stone.He tested by shaving some hair off his arm. Those knives never seen a strop and they were not sharpened during the next long day of cutting.

Forgive me, your question took me back many years ago when a small boy of six years was extremely impressed with his Grandpa's many talents.

ferg

quote name='sierraleather' timestamp='1341097363' post='254753']

Aside from your blade being chipped or it drags so badly it won't cut butter,what is your definition of "sharp", and how do you test or determine what is sharp,thanks

Edited July 1, 2012 by 50 years leather

[Sylvia]

My father was a butcher and meat cutter. And much like Ferg's Grandpa... shaving the hair off his arm was one method to test sharpness and when his arms were bare ... she would call my sister in. LOL.. I learned to make myself scarce when dad got to the "shaving" stage. . Another was to test it by cutting a piece of butcher paper. Basically you want your edge so sharp and polished that it takes NO EFFORT to cut. (It's the effort required to make the dull edge work is what makes it dangerous... And to make matters worse the dull edge tears instead of making a clean cut.. which complicates the healing process.)

[Itch]

We go through a lot of hides with every thing that we manufacture and that translates in to a lot of cutting with utility knives and blades.We sharpen a brand new utility blade as we find them dull when they are new.We use a piece of natural leather not the flesh side and rub it with bees wax and then push aluminum oxide powder in to it with the blade..This is usually followed up with jewelers rouge on another piece of leather..A well sharpened tool makes all the difference and is a pleasure to work with..Good Luck.

[pabloz]

There are many factors in any given blade that define "sharp" but most importantly is the application of the knife. In leather work I typically say the skiver or round knife is sharp when I can skive the thinnest tissue (catalog) paper I can find. On swivel knives it is a very subjective issue as some like to have an ULTRA smooth cutting blade while some like it to have a slight drag and others want it "perfectly dull"...no slicing just a dent. An 8000 grit mirror finish for my mentor, Jim Resley, was too smooth....he likes it at 1200 grit finish and then strop. Matt Whitaker defines trim knife/ round knife/ skiver sharp as "being able to cut through 8oz. leather with little effort and you cannot hear the leather being cut." Bob Beard defined swivel knife sharp as "it should swoosh through the leather." Jim Hay once told me the sharpest knife he ever saw "split a dollar bill in half" meaning through the bill separating the front from the back. Some people like a super smooth slicing action while others like a "toothy" feel. If you ask 100 people you will probably get 100 answers....again depending on the application. Skiving, slicing, trimming, swivel knife cuts, edge beveling, etc., etc., will all have differences. IMMHO sharp is what you percieve it to be. You can always reference someone or something else but ultimately you must define it for yourself.

There are tons of You Tube videos on sharpening and testing the edge. That would be a good way to get a visual definition.

Have fun and happy carving.

PZ

[pabloz]

Please allow me to add one more....based on some very dated research, the sharpest knife made by hand were Mayan (IIRC) surgical instraments made from obsidian. Due to the molecular makeup of this stuff they could knap it so cleanly that it could actually cut through, not tear, individual cells that they could not even dream of seeing.

PZ

[Glendon]

Looks like you've got your answer, but I'll pull out my old boy scout training and add my two cents. You should be able to hold a sheet of paper on edge and slide your blade right through it. If the blade resists, or you notice the pressure you're putting on the blade, it's not sharp enough. On something as easy as paper, a good sharp blade should just glide.

[amuckart]

Sharp is relative. It depends on what you're cutting and what you're cutting it with. Buy Leonard Lee's Book of Sharpening It'll teach you everything you want to know.

[TwinOaks]

One way to test 'sharpness' is to get a page from a magazine - nice glossy paper - and bend it in half. Not fold, just bend....so it has a nice roundness to it. A very sharp knife will bite into the paper and slice it. If it doesn't....back to the strop.

If we're talking about things other than cutting blades, my usual comment for an awl is "it should get half way through your finger before you feel it."

[pabloz]

  On 7/1/2012 at 2:53 PM, TwinOaks said:

"it should get half way through your finger before you feel it."

So glad to see I'm not the only one that's "been there, done that."

[Denster]

A quick way to determine if an edge is sharp. Look at the edge under a strong light. If you see any reflection it is not sharp.

[sierraleather]

  On 7/1/2012 at 5:11 PM, Denster said:

A quick way to determine if an edge is sharp. Look at the edge under a strong light. If you see any reflection it is not sharp.

Thanks to all of you for your information ,and I must apologize ,the knife I was referring to is the swivel knife,thanks again for your support.