Primary bevel or how obuse can you get

K

kwakn

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Oct 17, 2009
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I'm working on a few fixed blades from .25" cmp3v stock. The blade width will be 15/16". Blade length varies from 3.5" to 4.25". With these dimensions, a full flat grind = 15%. Visually, I like the heft of the .25 stock but concerned the knife will lose some of its "all around" usefulness if I leave it at this angle. I'm not trying to make it kitchen-slicing thin and will give up SOME slicing ability but I guess I'm looking for the maximum primary bevel angle for an "all around" blade profile. The obvious answer is to hollow grind it but I can't hollow grind yet...been practicing on wood and some cheap stuff but I'm not ready to take it to the 3v.
I made a few tweaks but this is the basic shape.

http://www.bladeforums.com/forums/showthread.php?p=7428599#poststop

Thoughts appreciated.
 
One of the biggest advantages of a high-toughness, high-edge-retention steel like 3V is that you can grind it thin and sharp, and it will still take more abuse than similar knives made from most other steels. Why 1/4" stock for such a small knife? :confused: I've used 3/16" for similar size knives, ground them full flat with full distal tapers, and frankly I still think it's a bit overkill thickness-wise.

Take advantage of 3V's toughness and grind those babies nice and thin.
 
James - Believe it or not, the 3v is what I had, kinda gifted, from someone elses leftovers. They were making tomahawks with integrated handles and their scraps were perfectly fine with me. I'm only on knife #5.

I did grind the first couple thin (rookie error) :o but what was left was a nice integral bolster. Once I figured out how NOT to make it thin, I started to question the obtuse angle.

I've only "read" how tough this steel is but don't have any real world experience with it yet.

I'll take this one to 3/16. That'll be 11.5 degrees. I can live with that even if it is a little overkill.
 
Don't get me wrong, a little overkill isn't necessarily a bad thing. If you have any more free 3V, let me know! :) It's good stuff.
 
3V ios great stuff an di have used a bit of it from small knives to full sized choppers


with your thickness and specs on the blade dependig on the HT i woudl take the blade to under .007 then sharpen with 10 degrees per side

it will be one hell of a stabing "shank" and i dont like that word but its sure a stabber
 
I'm not sure why you are calling 15 degrees an obtuse angle???? It is an impossibility for any knife to have edge with an obtuse angle.

A full flat grind at 15 degrees is a very acute edge of 7.5 degrees per side. A secondary bevel of 10 degrees per side will make a very sharp knife.
Hollow grinding does not reduce the edge angle. It reduces the amount of steel behind the edge to lighten and thin the blade while retaining a strong spine. The secondary bevel ( edge) is dictated by the use of the knife, the same as on a flat grind.
 
bladsmth said:
I'm not sure why you are calling 15 degrees an obtuse angle???? It is an impossibility for any knife to have edge with an obtuse angle.

A full flat grind at 15 degrees is a very acute edge of 7.5 degrees per side. A secondary bevel of 10 degrees per side will make a very sharp knife.
Hollow grinding does not reduce the edge angle. It reduces the amount of steel behind the edge to lighten and thin the blade while retaining a strong spine. The secondary bevel ( edge) is dictated by the use of the knife, the same as on a flat grind.
Click to expand...

Stacy, noted...bad word choice. I was looking for a succinct way get the concept across and perhaps took a bit too much 'license' in its use.
 
butcher_block said:
3V ios great stuff an di have used a bit of it from small knives to full sized choppers. with your thickness and specs on the blade dependig on the HT i woudl take the blade to under .007 then sharpen with 10 degrees per side. it will be one hell of a stabing "shank" and i dont like that word but its sure a stabber
Click to expand...

Butch, when you say take it to .007 is that before or after HT? There's a company in Pittsburgh that I'll ultimately send it to for this piece.
 
Yes, I believe you meant "How fat can you go?" Just being the semantics police.
Now days, a wrong word can end up as a Google hit in just days. A week after that it is a wikipedia definition - "Obtuse Blade Angle -any knife with a primary angle over 10 degrees."

The primary bevel is 90% determined by the blade thickness and the bevel height. Hollow/flat/convex actually changes it only a few degrees.
I would recommend that you do a full flat grind and then do the secondary at an angle determined by the function the knife will be used for. There is actually very little difference between the angle on any flat grind, as far as blade thickness or height goes.
on a 2" high blade the angle is 7 degrees for a 1/4" blade and 3.5 degrees for a 1/8" blade. Drop the blade to 1" and the numbers are 14 and 7. So, a 10 degree swing from a big fat blade to a small thin one. As you can see, the blade thickness is what you play with to make the knife a slicer. There is nothing wrong with a .060" thick blade.
 
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