How sharp is 24°

Jesse Smith

Jesse Smith

Joined
Dec 2, 2013
Messages
163
Hi guys, this is my first post here, hope this is the right place, and I'm not duplicating a question, but I did a quick Google search of the site and didn't find it.

I'm just finishing my very first knife. It's hunter/bowie material removal project using a Nicholson file. I'm pretty sure prettier knives have been made in prison, but I'll post pics when I get some finish on the scales.

Anyhow, I ran out and bought an EP Apex IV kit. Been wanting one for a couple years now, so this was a great excuse to buy it. ;) I decided to go with a 24° primary bevel since that seems to be the angle that Mr. Google says is best for a hunter. Also, this knife will never see any actual use, and it doesn't have a finger guard, so no use in going nuts and making it overly sharp.

But, now that I've sharpened it with all the stones up to 1000 grit, I'm not sure if it is as sharp as 24° should be, or if I just flubbed the sharpening somehow. It will kind of slice newsprint held in the other hand. The shiny stuff they use for ads, if that makes a difference. But, it doesn't do it very well. It'll slice a couple inches, then usually tear, and I can't just consistently slice off piece after piece like I can with the kitchen boning knife I sharpened to 15°.

So is that typical of a thick blade sharpened to 24° or do I need to go back through all the stones again?
 
Its typical of a thick blade; one that has not been taken to a zero edge or somewhere near there. Twenty four can be very sharp if its on a blade with good bevel geometry; which includes spine thickness, height of blade, steepness of bevel grind and finally the edge itself. If there is to much "meat" behind the cutting edge, the blade will not cut well no matter what the sharpening angle. Without seeing it; refine the bevels making the blade thinner at the edge. It takes a good bit of hand sanding to refine the bevels. Dull the existing edge before hand.
People that know tell me the edge begins when you start making the knife, choosing the steel and grinding the primary bevels. This is a common first knife result.

Enjoy the process and show us the result, Fred
 
Thanks Fred! That sounds like the problem. I know Dan308 (DT Knives) from a different forum and everyone seems to like how he leaves part of the file pattern on his knives. So that's what I tried doing with this one, plus I figured it would be less works since all the material removal was done by hand with a file. This is a THICK knife. The spine is the full thickness of the file, and the secondary primary bevel is short and steep.
 
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As sharp as you make it at 24 degrees. Is this inclusive or per side.

I strongly suspect that you arent all the way to the edge of tne edge in places.
 
Sadden said:
As sharp as you make it at 24 degrees. Is this inclusive or per side.

I strongly suspect that you arent all the way to the edge of tne edge in places.
Click to expand...

24° per side. Should that have been the total angle instead, for a hunter? Maybe I'll go back to the coarse stones and try again to make sure I did get all the way to the edge. The edge was pretty thick (compared to a knife that has actually been sharpened before) when I started so maybe there's a flat spot.

To be honest my eyes were going crossed trying to see what I was doing, and my fingers are so dry, calloused, and split up that I have a heck of a time feeling a burr even with the coarse stones.
 
Sadden said:
As sharp as you make it at 24 degrees.
Click to expand...

Yup. Sharpness is independent of angle. What I think is being confused here is sharpness and ease of cut. Sharpness is simply a factor of how refined your edge is. Imagine a perfect edge as a triangle. Any wear on your edge will be wearing the top off of that triangle, turning it into a trapezoid, with the "edge" being the now-flattened top. EVERY edge, if viewed under sufficient magnification (like an electron microscope) will look dull compared to with the naked eye. Sharpness is all about removing material from the sides of that triangle in order to bring that trapezoid back to triangular form. The narrower the distance spanning the bevels, the sharper it is.

However, ease of cutting is determined by how thin the geometry is (including how sharp the edge is, since that's a matter of "thinness") and that's where edge and bevel angles come into play. The closer you get to the edge, the greater the influence the thickness has on performance, so it's most important for the very edge and the region right behind it to be thin. The rest of the geometry still plays a role, but to a lesser and lesser degree the further you get back from the edge. This is exactly why it's common for cheap kitchen knives to be made in thin stock with a hollow saber grind--it's the cheapest and easiest way to manufacture a knife that can still cut "well enough" (even if it's far from the ideal.)

And for a hunting knife the angle would depend on the specific uses and the skill of the user. Personally I agree that dropping it down to 12° per side for a TOTAL of 24° would be best, but I know plenty of guys who would be prone to damage an edge that thin because of their level of skill with the tool and the uses they have for it.
 
24 per side=48 inclusive. Sounds like a good hunting knife edge if you associate hunting knife with hard use. 24 per side will produce a very tough edge and will take abuse better. 24 inclusive would be VERY thin and not something I would associate with outdoors at all, very thin and prone to rolling and chipping I would think. YMMV
 
There's not much out there that can be skinned and capped with a 48 degree inclusive edge. I think it a good angle for a splitting maul. Most every hunter I make carries a 24 inclusive edge with maybe a 30 degree micro bevel. If the heat treat is done correctly with the edge not being left overly hard a 24 degree inclusive edge is very applicable for out door use. A working knife for hunters holds up well at HRC 59 for most purposes. At this hardness rating coupled with proper heat cycling an edge will deflect and return to normal quite easily.
Most kitchen slicers are in the 22 degree inclusive range and are carried on a thinly ground bevel. Filet knives work well at 22 degrees. Machetes are something I grind with a 35 degree inclusive edge, being built for abuse.

A 24 degree inclusive secondary bevel would only be considered thin on a thinly ground bevel. Blades should be built to carry the edge needed for the work being done.

Fred
 
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