Edge holding!

S

sinawalli

Joined
Aug 20, 2003
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I am a amateur knife maker, who has made several knives. I use a flat grind, and a convex grind, my steel (CPM D2, D2, CPM 154, and 01) is professionally heat treated to around RC 61. Why don't my blades hold a edge for very long? I can't dress and skin a deer without it going dull. I've read that lots of makes knives can stay sharp after several deer. My steel is 1/8" to 5/32" thick. What am I doing wrong? Thanks!!
 
Who does your HT and posting their exact process may help the more knowledgeable folks here answer your questions. I am aware that most of those steels need cryo to garner their optimum performance and if there is a snap temper before the cryo it could be detrimental to the performance.
 
not quite.
 
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I would work on my edge shaping to make it easier to sharpen, ie thinner and if that doesn't work get someone who is experienced to teach you to sharpen properly.

Your choice of steels is pretty good so I can't fault you there unless you are trying to forge stainless steels as this usually causes carbon depletion.

George
 
If the heat treat is handled correctly, both the D2 and O1 blades should be able to get thru several deer with no problem - certainly we need some more info there. Your blade stock thickness sounds good, you're not making sharpened pry bars -- what sort of thickness are you getting say 0.2" or so in from the edge? Possibly too much shoulder thickness behind the edge (and what's your edge angle?). Another possibility with D2 in particular is that it's *too* hard - if it's winding up harder than about 61, you could have a problem there (basically, most D2 at 62-63 will cut meat forever, but will dull almost instantly if even scraped against bone or cutting thru a muddy hide).

Oh, another thing -- what sort of edge are you putting on these steels when you sharpen them -- if you're going for a polished edge, that may be part of your trouble.
 
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zerogee said:
If the heat treat is handled correctly, both the D2 and O1 blades should be able to get thru several deer with no problem - certainly we need some more info there. Your blade stock thickness sounds good, you're not making sharpened pry bars -- what sort of thickness are you getting say 0.2" or so in from the edge? Possibly too much shoulder thickness behind the edge (and what's your edge angle?). Another possibility with D2 in particular is that it's *too* hard - if it's winding up harder than about 61, you could have a problem there (basically, most D2 at 62-63 will cut meat forever, but will dull almost instantly if even scraped against bone or cutting thru a muddy hide).

Oh, another thing -- what sort of edge are you putting on these steels when you sharpen them -- if you're going for a polished edge, that may be part of your trouble.
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Will take a couple to work tomorrow and measure them. Not sure what you mean by "edge angle"! I sharpen them with a Sharpmaker at 40 degrees included. By a polished edge, do you mean stropped? I do strop them, and they become very sharp, just don't last long!! Thanks!!
 
george tichbourne said:
I would work on my edge shaping to make it easier to sharpen, ie thinner and if that doesn't work get someone who is experienced to teach you to sharpen properly.

Your choice of steels is pretty good so I can't fault you there unless you are trying to forge stainless steels as this usually causes carbon depletion.

George
Click to expand...

How do I work on my edge shaping? Any tips will be appreciates!! Thanks!!
 
My personal observations regarding highly polished edges are that a paper slicing, hair whittling edge will slice paper and whittle hair for a little while but won't do much of anything else for very long at all.

My most impressive cutting edges have been ground on a 150 belt and strop just enough to knock the burr off. It may not pop or whittle hair or slice paper as well as a buffed edge but it will cut just about anything else for as long as I want.

Seems the consensus for hunter/skinner is 22 - 25 degrees included. I think my axes are more acutely edged than 40 deg. :)
 
Seems the consensus for hunter/skinner is 22 - 25 degrees included. I think my axes are more acutely edged than 40 deg.

Are you sure on that? My Sharpmaker by Spyderco has a 40 degree included angle on it.
 
I remember reading a thread where most of the guys were using around 12 degrees per side for skinners, I'll see if I can find it.
 
How are you sharpening your knives?

D2 and 154CM like a "toothy" edge.

Some very well known makers use a 350 grit belt to sharpen their knives, makes a nice edge, but if you want an aggressive edge that will cut meat, try sharpening with a 180 to 220 grit belt and stropping on leather. ;)

I tried the 350 grit belt this year, but I'm going back to the toothy edges from now on.
 
Yes, 22-25 degrees *included* is correct - 11-12.5 degrees per side for typical use. The whole thing with 40 degrees included is done so that the usual consumer knives (made with steel that would shame a butter knife) won't immediately fold the edge on the first thing you cut. I sharpen on bench stones -- my angle per side is just a smidgen more than 10 degrees -- if you lay your knives down at this angle and you can see that your edge is in the air -- meaning, you're laying on the shoulder behind the edge -- then you know where to start - bring that shoulder down (you might want to use a magic marker to color the edge bevel and the shoulder behind it - lay your knife down at just over 10 degrees and make a few sharpening strokes - now see where the color has been removed). Otherwise you won't even be able to get to your edge to sharpen it properly.

Also - agreed on the toothy working edges. I typically use a medium or fine diamond stone to set the edge, then give it a few light strokes on a fine ceramic to refine the edge a little, then strop it a few times on some plain "dry" smooth leather (no compound).
 
zerogee said:
Yes, 22-25 degrees *included* is correct - 11-12.5 degrees per side for typical use. The whole thing with 40 degrees included is done so that the usual consumer knives (made with steel that would shame a butter knife) won't immediately fold the edge on the first thing you cut. I sharpen on bench stones -- my angle per side is just a smidgen more than 10 degrees -- if you lay your knives down at this angle and you can see that your edge is in the air -- meaning, you're laying on the shoulder behind the edge -- then you know where to start - bring that shoulder down (you might want to use a magic marker to color the edge bevel and the shoulder behind it - lay your knife down at just over 10 degrees and make a few sharpening strokes - now see where the color has been removed). Otherwise you won't even be able to get to your edge to sharpen it properly.

Also - agreed on the toothy working edges. I typically use a medium or fine diamond stone to set the edge, then give it a few light strokes on a fine ceramic to refine the edge a little, then strop it a few times on some plain "dry" smooth leather (no compound).
Click to expand...


Will definitley give it a try! Thanks for your help!!:D
 
There are three possibilities I can think of:

1: the steel was not soaked long enough during hardening
2: the steel did not get cooled to Mf
3: the edge was over heated during post HT grinding or sharpening

I personally have skinned two deer back to back with D2 and it would still shave hair, and this includes plenty of moderate bone contact such as cutting out the back straps. And I have received feedback of much more than that (I've never personally skinned seven deer in a row - but some people have)

I like it at HRC 61-62 sharpened 26 deg included. It is important to quench to Mf (about -100 F, technically not cryo) or it suffers excessive retained austenite (a cause of edge weakness) that can then only be addresses with a higher temperature temper (which also reduces edge stability).

Your "professional heat treat" may not be that good. Most machine shops don't know how to process steel that will be used as a blade. Mine didn't.
 
I am positive that the problem doesn't lie in the heat treating. My heat treating goes to a very accomplished local knife maker/ member of this forum, and his own knives perform very well. Pretty sure it is something I am doing with my edge geometry.:(
 
I just wanted to add that a great simple test of a working edge (and edge geometry) is just to get a bunch of corrugated cardboard and start slicing it up -- hold your blade at about a 45 degree angle to the surface of the cardboard so that you cancel out most of the effort of just pushing the thickness of the blade thru the cardboard and can concentrate on the quality of the cutting instead.
 
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