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Author Topic: Question begging to be asked  (Read 2435 times)
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John Silveira
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« on: November 12, 2013, 05:07:50 AM »

I've been studying the Ed Fowler grind !  The convex grind.  The blade is convex starting from the plunge and then the blade thickens toward the front all the while maintaining a convex grind.  Makes great sense to me structural integrity and strength built right into the blade....   I'll make one yet as soon as i wrap my brain around how to pull off the grind.........   The Question :

I like razor sharp knives ...  Thin blades seem to get razor sharp more easily than heavy ones ( i'm probably wrong about that - it's all a matter of expertise i suspect ) - anyway,  Do those big convex grinds get as razor sharp as any other type of grind ?   Just seems to me like it might be a bit more tricky to sharpen than a flat grind for example ...     Use a slack belt to sharpen these convex grinds ?  finish off with a diamond stone ?

cheers                 Yes !  I'm gona make a Fowler design you just watch  Cheesy

PS. changed my profile pic .  it's my very first forged blade.  cut from a piece of coil spring from a car - bout 1" round to start.    I didn't have the skill at the time to do the grinds i knew i'd ruin it so the blade has been sitting on the sidelines in just that condition in the photo for about 4 months now.  I'm so close to finishing it out ......   Love the little thing .....       
ciao    

« Last Edit: November 12, 2013, 05:11:20 AM by John Silveira » Logged
wnelson aka. dedox
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« Reply #1 on: November 12, 2013, 02:23:03 PM »

The other guys can probably answer this better than me but, it all depends on what purpose you have intended for the knife. For example: if it is a knife intended for shaving and little whittling tasks close to the house, it can be a thin, hollow or flat ground blade. but, if you are going to take it far away from your house where there isn't medical attention that can be there quick, I would suggest a thicker, convex knife meant solely for the purpose of survival and just altogether rough jobs. But, as I said before the other guys can probably answer this better than me. Good luck!
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mreich
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« Reply #2 on: November 14, 2013, 01:51:02 AM »

I would basically agree with WNelson.

You can make a thick blade or a thin blade with the same edge geometry. A thick blade will just have a much wider edge bevel, if that's what you want.

I do that often.
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John Silveira
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« Reply #3 on: November 14, 2013, 05:53:00 PM »

I would basically agree with WNelson.

You can make a thick blade or a thin blade with the same edge geometry. A thick blade will just have a much wider edge bevel, if that's what you want.

I do that often.

OK , i think i understand.    Although my question wasn't really meant to be a discussion of thick or thin blades , i probably should have just made it more simple and said -  " Do convex grinds get just as razor sharp as any other kind of grind "....         Sounds like the answer is yes .......

I was under the impression that a convex grind did NOT have an Edge bevel .....    Thought the convex grind just goes convex all the way to the sharpened edge.......   So on Ed's blades/grinds for example then, they are convex but also have an edge bevel if i'm understanding this correctly ......    and the question still remains - "Convex grinds can get just as razor sharp as any other grind "....

cheers   
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PhilL
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« Reply #4 on: November 14, 2013, 07:44:38 PM »

"Convex grinds can get just as razor sharp as any other grind "   

I'm not a maker or the definitive answer to any technical questions, but from my perspective, of course you can get a "hair popping" edge on a Convex grind.
But, I think of the knives I own that are convex or Modified Price grind (alla Ed Fowler) as more of a working edge. I want my knives sharp, but not too an ultra refined polished edge. I want it a little 'toothy', with some meat behind the edge. If I wanted a razor, I'd get a razor.
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Dennis Mashburn
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« Reply #5 on: November 14, 2013, 10:29:29 PM »

I am certainly not the ultimate expert, but yes you are correct.  Convex can be as sharp as V or hollow.  The thickness of the blade does play a role in this.

I also sharpen some knives with the sharpened edge also being convex.  When I use the belt grinder even in a low slack area of the belt it will have a bit of a convex shape to the sharpened edge.  If I use a stone the sharpened edge should be a flat V type shape.  Either way they can get really sharp.  The flat is easier for most folks to sharpen though.
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Ed Fowler
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« Reply #6 on: November 14, 2013, 10:59:21 PM »

When I sharpen a blade with a convex grind I blend in the edge to the rest of the blade. You can go shallow or deep, but even when sharpening a flat ground blade I blend it into the rest of the blade rather than leave a sharp angle behind the edge.
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John Silveira
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« Reply #7 on: November 15, 2013, 11:19:41 PM »

"Convex grinds can get just as razor sharp as any other grind "   

I'm not a maker or the definitive answer to any technical questions, but from my perspective, of course you can get a "hair popping" edge on a Convex grind.
But, I think of the knives I own that are convex or Modified Price grind (alla Ed Fowler) as more of a working edge. I want my knives sharp, but not too an ultra refined polished edge. I want it a little 'toothy', with some meat behind the edge. If I wanted a razor, I'd get a razor.

just want to add to the conversation :   
I used to sharpen all my friends knives when i was a kid ( well in my early 20's ) and using those little hand held stones would always get shaving sharp blades - i wasn't satisfied till the blade would shave hair. 

Then i just recently got back into knives except now making my own blades ....  Something changed for me - i became more aware of every aspect ( lots more to go for sure ) but actually started examining the edge of my blades while sharpening under magnifying glasses.   I was under the impression the absolutely more refined i could get the edge the better it would cut/shave including the paper cutting test. I found as i got the edge to a fine POLISH it didnt seem to cut the paper worth a darn and shaving hair became harder...  Frustrated the hell out of me -  for a while i thought i was overcooking the steel on my blades and i was ruining the grain and there was something wrong .......

So i went back to square one -  use a coarse stone to cut the bevel i wanted ( not a steep one but shallow like 10* or less )...  Then - i have a 4 sided diamond sharpening block 200/300/400/600 .. Again i'd cut the edge in with the 200 - then go to 300 and the blade got razor sharp again at the 300 level ..... Could slice through paper with ease , hairs come popping off my arm with ease ( got bald arms to prove it at the moment ) ..  Then 400 grit , ya can feel it refining the edge , it glides over the diamond 400 grit very smoothly ... 400 cuts through the paper very easily and hairs too -- and i'm looking at the edge through a magnifyer 10x ..  I went to the 600 grit and now it's starting to smooth out the surface of the edge on the blade pretty good - starting to look polished -  Still cutting hairs/paper with no problem ...... But then i started touching up the edge with the 1200 grit ceramic stone i have and the finer it seemed i got the edge the worse it would cut paper including hair ....    The already long story slightly shorter is what seems to produce the best cutting edge for me is the 300 / 400 grit diamond stone and i don't goo all krazy trying to polish the edge to a microscopic perfection...   I will give it a pass or two on a strop after the diamond stone but it's almost like i like the raw straight off the diamond stone the best 300/400 grit....

It's like you say Phil -- the toothy edge is cool .... Just so happens it's as sharp as a razor anyway. At least that's my finding , yours may be different  (=

Ed. i'm surprised hearing that/how you blend your edges into the rest of the blade... Cool

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« Reply #8 on: November 22, 2013, 07:03:15 PM »

John: blending the edge into the blade is the way my grandfather taught me way back in the 40's. He stated:

"when you don't blend the edge to the blade you do no favors to the knife. It is OK to put a quick edge on a knife when you don't have time to blend it in, but always blend it when you have time."

He also used a steel most of the time. Steel still work well and maybe that should be my next article in Blade.

Radicat: That is an excellent Idea! Reminds me of how sharpening evolved from softer black combination stones which were lubricated with spit, to very costly sharpening oils. Thanks for sharing your work with us!
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mreich
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« Reply #9 on: November 24, 2013, 09:15:36 PM »

Thank you for the kind words, Radicat!  Smiley

I use a lot of compounds on leather hones and linen belts. I've never heard of any that are bad for your health, but I've only ever gotten compounds from two of my good friends, who actually formulate them themselves. They are both very popular among fine sharpening circles.

I professionally sharpen around 1,000 knives/year. I would not be nearly as interested in doing this if I didn't have three 1x42" Kalamazoo grinders, with linen belts loaded with cubic boron nitride (CBN), in various grits and formulations.

I also really like detergent based 1 micron (16,000 grit) boron carbide (black diamond) on a leather belt. I haven't found anything else that will so completely remove a burr, especially on soft stainless steel, and still leave enough tooth.

I do use straight razors to shave my face, as do many of my blade aficionado friends. I don't think I can explain how sharp an edge gets when you finish with .025 micron (that's about 640,000 grit) poly diamond compound on kangaroo hide or nano cloth, backed with glass.

These compounds work amazingly well, and both of my friends are internationally known for the quality of their products.

Sorry for seemingly going off topic, but when guys start talking about edge geometry and "toothy-ness", I can have a lot to say.

I should ask, "How far down this rabbit hole are you willing to go?" It's probably much deeper than you ever imagined it possibly could be.

If you want to learn about sharpening, the "Keeping Sharp" forum on Knife Forums is where you'll find the best information.   

I'm definitely Not saying there's anything wrong with whatever y'all are currently doing. There aren't many people who take the plunge into sharpening professionally, and looking at edges under 400x magnification. It just happens to be fun for me.

These are my own fine head hairs. (about .00150", measured with a Starrett micrometer)

In the first picture, the hair on the right has been split into thirds.

The last one, as you can see, has been split for over 3mm.

This is what first got me heading down the rabbit hole.





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Daniel Rohde (D-Vision)
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« Reply #10 on: November 24, 2013, 10:10:06 PM »

Radicat: Nice post! Wink
Mreich: sounds like that's pretty fine grit!! do you sharpen all your knives to that fine of grit(640,000)? how does Murray Carters sharpening compare to yours? some time I think I'm going to get some more sharpening stuff(finer stones and strops etc...) sounds cool.
Thanks
DV...
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mreich
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« Reply #11 on: November 25, 2013, 04:20:10 PM »

Lord no. I don't even hone my razor to that degree very often.

It's just the limit we are currently at.

I usually stop at 8 micron on knives. That's 2000 grit.

If I can detect any presence of a burr, I do one of two things.

I go to 4 micron, which is about 4000 grit, and that rarely leaves any burr on hard steel.

If I'm sharpening high alloy stainless ("super steels"), like S30, S35VN, M390, Carpenter CTS, or the like, it can be difficult to completely remove the burr from these very wear resistant steels.

I just refine the burr off with the leather belt, then go back to the 2k grit CBN for a pass on each side.

Murray has two stones, and I've never seen him waver in his sharpening. He uses a King 1k and a King 6k when he hand sharpens every single knife that leaves his possession.

If he wants a keener edge, he strops on a piece of newspaper, laid on his 6k stone. That's the edge he shaves with.

Guys who are seriously into straight razors rarely stop before 0.50u (one half micron, or 32,000 grit) compound on a hone. More often they at least take that 0.50 edge to a bare horse butt leather hone. Lots of them use compound down to 0.10u (160,000 grit).

You can't really compare straight razors to knives though.

Most people are pretty blown away with a clean 2k edge. 4k is usually tree-topping arm hair. 8k is a pretty polished edge, and the minimum for straight razors.

There is a big difference in a knife sharpened at 15 degrees per side (30* inclusive), and a straight razor at something around 5* per side.

Sharpening is a very broad subject.
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John Silveira
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« Reply #12 on: November 27, 2013, 02:50:58 AM »

Right when i thought i discovered something about sharpening i get a game changer lesson like the one above    Tongue
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mreich
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« Reply #13 on: November 28, 2013, 03:39:02 AM »

I would totally run down to the Willow Bow whenever I'm invited.

About all it takes is a call from Ed or Chris.
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