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TOPIC: What is "Sharp"

Re:Re: What is "Sharp" 4 months 2 weeks ago #16549

  • tcmeyer
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As mentioned earlier, I bought a box of scalpels from Amazon. I was just curious as to what made them so sharp. These blades only cost about 13 cents each, so I doubt if they're the best available. Given the subject of this thread, I thought I'd share the photos with you.

The blades are 0.015" thick and the single bevels are ground to an included angle of about 27 degrees. (An earlier disposable scalpel I'd gotten from a dentist friend was 0.040" thick and ground off-center to an included angle of 30 degrees.)

The first photo shows side-by-side sections of the scalpel as viewed from both sides. Both sides seem to be ground with about an 800 grit. You can see that one side is polished and the other side is not.

You'll see in the second photo, which shows a cross-section of the blade, that the polished side has rolled what amounts to a heavy burr to the unpolished side.

When testing the blade on my thumbnail, it was immediately apparent that the blade would bite with the burr facing down. When it was facing up, I had to raise the angle quite a bit to get a bite.

After using my Wicked Edge system for a couple of years, I have to say that I'm not all that impressed by the "sharpness" of scalpels.

newscalpeloverlay.jpg



newscalpelendview.jpg
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Re:Re: What is "Sharp" 4 months 2 weeks ago #16562

  • tcmeyer
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Here's a "heads up." Tonight, (late Thursday night) I watched an episode of "How It's Made" on the Science Channel (DIRECTV CH284). They had an interesting clip on the manufacturing of Solingen straight razors.

They distinctly showed how the primary hollow-grind is done, but didn't show how the secondary bevel was done. The secondary bevel was quite wide, somewhere between 6 and 8mm. Anytime you see a very wide bevel, it's either a very acute angle or a very thick blade. They showed how thin the blade was along the edge by pressing it (flat side) against a wide metal ring the person was wearing. You could clearly see the edge flexing as the blade was pressed against the ring. They suggested that the edge approached the thickness of foil.

No doubt. Extremely thin blades with extremely acute secondary bevel angles make for extremely sharp edges. Also no doubt that you'll have to have a high quality steel which will support that kind of geometry.

If you want to see this episode, it is being rebroadcast at 2:30AM CST Saturday morning on the Science Channel (DIRECTV SCIHD 284). If you have the Science Channel on your local cable service, check the listing


If you don't have DVR service, we need to have a personal talk.
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Re:Re: What is "Sharp" 4 months 2 weeks ago #16566

  • leomitch
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Solingen's best steels are excellent. When I was 15 I bought a Solingen Bowie Knife for the princely sum of $9.95 at Lefevre's Sports Shop in North Bay. Actually that was big money then, but I came back from Cadet Camp at Ipperwash with $20 dollars in my pocket. I put this knife through hell trying to get down the technique of throwing it overhand and underhand from 10 feet. Oh my! The bone handle eventually cracked, but that blade remained sharp and undaunted until one day it struck a nail in the wooden extension of my Dad's old garage and it ricocheted and bounced off a boulder. The tip broke and the edge was a mess. Good steel that Solingen knife.
As for my Dad's garage extension which was added to accommodate our new 1950 Chevy, it was so weakened by my efforts it had to be rebuilt and there went my other 10 dollars from Cadet camp. I also got the rest of the summer working at my father's restaurant doing dishes and carrying pop cases and ice from the back to keep the Coke cooler full. Bad Leo!!

Leo
Never go anywhere without your knife!
Gibbs rule number 9

Leo James Mitchell
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Re:Re: What is "Sharp" 4 months 2 weeks ago #16570

  • cbwx34
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tcmeyer wrote:
If you want to see this episode, it is being rebroadcast at 2:30AM CST Saturday morning on the Science Channel (DIRECTV SCIHD 284). If you have the Science Channel on your local cable service, check the listing.

If you don't have DVR service, we need to have a personal talk.

Or.....



:)
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Re:Re: Re:Re: What is "Sharp" 4 months 2 weeks ago #16572

  • razoredgeknives
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GibCurry wrote:
razoredgeknives wrote:
.....It went from around .040" thick to about .010". .....

Josh

Very nice.

Just wondering.... do you (and others?) put the micrometer on every blade?

Actually, I didn't measure these at all (I forgot) but I know what .010" looks like :-)

Josh
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Re:Re: Re:Re: What is "Sharp" 4 months 2 weeks ago #16573

  • razoredgeknives
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LeoBarr wrote:
They should work beautifully for slicing not on crusty bread though they could roll on that .
What make is the western handled Japanese parer ?

Why would they roll on bread more than hitting a cutting board repeatedly when cutting vegetables? Just curious :-)

I'm not sure... A name I hadn't heard of before, I ground it off lol

I got feedback from my customer though! He loves them :-)

Josh
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Re:Re: What is "Sharp" 4 months 2 weeks ago #16575

  • LeoBarr
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I thought I would share this I bought this little Global peeler I reckon it is sharpened with sub 400 grit and polished off a little on a leather belt it is quite handy for what is a sharp knife and what is adequate refinement for a low level Japanese knife or a high level European knife. Note it is a convex edge 10-15˚. I have sharpened lots of Globals but not seen how they are out the factory it supports Eamon's observations not refining the edge too far.
The magnified view is 400X with a Veho.
ScreenShot2014-03-13at11.25.16.png


IMG_1704.JPG


IMG_1703.JPG
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Re:Re: Re:Re: What is "Sharp" 4 months 2 weeks ago #16577

  • LeoBarr
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I read somewhere recently that some rather crusty bread rolled a knife the board is less likely to since the crust of the bread was probable unevenly hard where as the board is an even hardness & it is more likely that a larger part of the knife hits the board.
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Re:Re: Re:Re: What is "Sharp" 4 months 2 weeks ago #16578

  • LeoBarr
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They looked really good.
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Re:Re: Re:Re: What is "Sharp" 4 months 1 week ago #16598

  • LeoBarr
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higher grit finishes cause
less damage to food
slower oxidization of food after cutting
less water loss
higher gloss/sheen of cut surfaces
less grip/tactile feedback
less ability to dig into thick skinned items
Lower grit finishes cause
greater damage to food
faster oxidization
greater water loss
matte looking cut surfaces
better grip of the edge/improved tactile feedback
greater ability to "dig in" to thick skinned items
increased ability to feel sharp
the actual edge sharpness will diminish at almost the same rate regardless of finish except that toothier edges retain the feeling of "bite" longer
german knives- 600-3000 grit
japanese knives 3000-8000 grit
chefs knives 3000-6000 grit
slicers 4000-8000 grit
butchery knives 3000-4000
these are some figures that Jon of Japaneseknifeimports gave me obviously the chefs knives mentioned would refer to Japanese knives so the cheap knives European types are best on 600-3K depending on quality and Chinese knives I would finish at 400 whilst the best German knives I would treat more like a Japanese knife.
I think in sharpening for a customer it is important to know what the knife is to be used for a go to knife may be used to slice through food in plastic packets to soft tomatoes so that should have a low grit finish where as a dedicated slicer or carving knife will perform best with a refined edge . If a chef offers no info on the use of the blades then I guess lower grit blade finishers are best since they probable do not have much knife discipline .
It is still a difficult question since someone may try to test the sharpness by shaving hair in which case the more refined edge will win but hopefully the real test is how they perform in the kitchen.

Leo Nav
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