Sharpening angle question.

jdm61

jdm61

itinerant metal pounder
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Aug 12, 2005
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I am making a couple of prototype bushcraft/outdoors knives in CPM 3V. What included sharpening angle would you guys recommend?
 
These are not large knives. 4.25-5.5 inch blades.
 
Most axes sport a 30 to 35 degree inclusive angle at the edge. With your blades; both the thickness of the spine and the thickness at the edge before the cutting edge is applied should be considered. If the edge has been taken to zero before sharpening a less acute angle is advised. If the edge is left a bit thick before sharpening a more acute angle can be ground without risk of chipping. You could grind a 24 inclusive on the thin edge where is you could take the thicker edge to a 20 degree inclusive.

No one angle can be applied to a "class" of knives without knowing the specifics of a blades geometry.
 
Flat grind, all geometry about the same. 1 1/4 wide with .207 stock, 1 1/8 with .172, etc. all will be taken down to .020 MOL. So a 30 would work?
Fred.Rowe said:
Most axes sport a 30 to 35 degree inclusive angle at the edge. With your blades; both the thickness of the spine and the thickness at the edge before the cutting edge is applied should be considered. If the edge has been taken to zero before sharpening a less acute angle is advised. If the edge is left a bit thick before sharpening a more acute angle can be ground without risk of chipping. You could grind a 24 inclusive on the thin edge where is you could take the thicker edge to a 20 degree inclusive.

No one angle can be applied to a "class" of knives without knowing the specifics of a blades geometry.
Click to expand...
 
Joe, I'm interested in the answers you seek as well. I'm planning on ordering some 3V soon too.
I think with CPM3V you could .172 or thinner for both knives. Take em to .020 and a 20 degree or less edge. 3V's toughness and wear resistance should both allow for a much thinner edge, and also thinner edge is helpful for ease of sharpening.
I did some searching and found 3V blades down to a 10 degree edge. Hmmmmmm.....
 
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make sure that is not 10 agrees per side, Brian. I don't even think that the craziest of the Japanese kitchen guys go to 10 agree included angle. ;) .020 is the starting point as the heat treat guys tell you to leave it thicker than .015 when you send it to them.
Brian Ayres said:
Joe, I'm interested in the answers you seek as well. I'm planning on ordering some 3V soon too.
I think with CPM3V you could .172 or thinner for both knives. Take em to .20 and a 20 degree or less edge. 3V's toughness and wear resistance should both allow for a much thinner edge, and also thinner edge is helpful for ease of sharpening.
I did some searching and found 3V blades down to a 10 degree edge. Hmmmmmm.....
Click to expand...
 
Yeah, I know about the edge thickness for HT. I spent over an hour looking at old posts in Shoptalk, and for sale threads and have seen several CPM3V knives with edges down to .0150, HRC 60-61 and the most acute edge angle was 12 degrees(6 per side)......:(:confused:
Most of the thinnest edges I found were .0150 with a 20 degree bevel and 60-61 HRC..

Maybe Butch will see this or I'll e-mail him since I know he uses CPM3V.

I guess I am just wondering as I'd like maximum performance and if paying extra for the steel I'd hate to lose out on the advantages of the toughness and wear resistance.

All I've read is that with 3v thinner is better...But, I'm a total newbie and am just trying to figure this out!:D

Can't believe everything you read on the net....:rolleyes:
 
On my 3V outdoor knives I grind to .010" before sharpening, and my chef in 3V I made was ground to .005 before sharpening. I also have a 12" blade chopper that I ground very thin to test edge toughness. I ground it very thin to see what the 3V could handle, took it to .010" and sharpened. Has held the edge remarkably. I did some very aggressive chopping with it in very seasoned wood to further stress the issue. I did some intentional torquing and prying and managed to cause the edge to deflect, but was able to straighten with my multitool. I would not grind a customers chopper that thin unless they asked for it and knew the downfalls. I was pleased because in my mind under normal usage 3V can handle some heavy usage in a thin edge cross section.

With all the above said I would say you would be fine to grind your blades to .010" after heat treat and then sharpen to a 20* inclusive. That combination should give you some great slicing results.

Good Luck

Chris
 
Brian Ayres said:
3V's toughness and wear resistance should both allow for a much thinner edge, and also thinner edge is helpful for ease of sharpening.
Click to expand...

That really is true in my experience, and that's the whole point of using 3V for knives. For goodness sakes, sand/polish it as fine as you want before HT.
One way to know for sure is to take one of your blades to even thinner and more acute than you think is practical, and use it for whatever purpose you designed it for*. If it chips or rolls, it's easy to knock the edge back to being thicker and/or less acute. As Chris said, you may be pleasantly surprised by how thin/keen you can go with this stuff. Everyone I know who's used it a lot has recommended 58-59Rc for big choppers, and 60-62Rc :eek: for small, more delicate-use 3V knives.

*I'm not talking about chopping 2x4's with a fillet knife or breaking cinder blocks with a hunter. :rolleyes:
 
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