bad knife or bad technique?

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xxspeakxx

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Jan 26, 2014
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I bought a new sharpener today.

A smith's diamond tri-stone. Offers a coarse diamond stone, fine diamond stone, and polishing arkansas stone.

I went to touch up some of my knives starting with my cheap winchester hunting knife, followed by my case xx, and finally going over my K-bar short.

The other two knives came out nice and sharp with no issues, but the k-bar just would not take an edge. I spent 3 hours working on it before it finally came to an edge but I wouldn't call it "sharp" more like "sharp enough".

The edge would look polished, when I ran my thumb across it felt sharp, but when I tried to cut a sheet of paper it would snag and tear at best but not cut. I took the edge completely off twice and started from zero to try and bring it up to snuff, before finally giving up.

I sharpened it like the others. Holding the blade at 25 degree angle and sliding it across the stone twice on each side in a slicing motion. Applying pressure at first and then after a few strokes lightening up until it's just the weight of the blade doing the work and finishing on a leather strop block.


The winchester is 440 I believe and I know the case xx is a carbon steel. Neither have the heft that the k-bar has on it although the case xx comes close to length and I'm used to sharpening the chef's knives where I work so I doubt it's a size issue. I wouldn't rule out the material as the possible culprit to this.

Any idea on what might be happening here?
 
Sounds like your not sharping all the way down to the cutting edge. Get a magnifing glass to confirm also burr forming is a solid confrimation a new edge is being made.
 
xxspeakxx said:
I bought a new sharpener today.

A smith's diamond tri-stone. Offers a coarse diamond stone, fine diamond stone, and polishing arkansas stone.

I went to touch up some of my knives starting with my cheap winchester hunting knife, followed by my case xx, and finally going over my K-bar short.

The other two knives came out nice and sharp with no issues, but the k-bar just would not take an edge. I spent 3 hours working on it before it finally came to an edge but I wouldn't call it "sharp" more like "sharp enough".

The edge would look polished, when I ran my thumb across it felt sharp, but when I tried to cut a sheet of paper it would snag and tear at best but not cut. I took the edge completely off twice and started from zero to try and bring it up to snuff, before finally giving up.

I sharpened it like the others. Holding the blade at 25 degree angle and sliding it across the stone twice on each side in a slicing motion. Applying pressure at first and then after a few strokes lightening up until it's just the weight of the blade doing the work and finishing on a leather strop block.


The winchester is 440 I believe and I know the case xx is a carbon steel. Neither have the heft that the k-bar has on it although the case xx comes close to length and I'm used to sharpening the chef's knives where I work so I doubt it's a size issue. I wouldn't rule out the material as the possible culprit to this.

Any idea on what might be happening here?
Click to expand...

You're microbeveling and your angle is too small to reach the apex
Try increasing the angle from 25dps to 30dps or 40dps or even 45dps

If that doesn't get sharper in under 10 strokes,
you're going to have to work on the edge bevel (20dps) with coarse stone ... some 60-300 strokes ought to do it , then microbevel at increased angle like you've been doing (this also cuts off the burr)

Here they're talking about ka-bar having 20dps to 30dps edge http://www.bladeforums.com/forums/showthread.php/966474-Sharpening-the-Ka-Bar-USMC

If you're trying to microbevel, that is a few strokes at elevated angle to get it sharp, it has to be elevated enough to touch the apex ... if the edge bevels is 20-30dps you need at least 30-40 dps to touch apex

Before I figured stuff out, I was trying to microbevel at 25dps when the edge was at at 20dps but I hadn't raised a burr yet ... not enough time on the coarse stone to where microbeveling would get it sharp in under 10 strokes

raising a burr is one way, another is looking for reflection with flashlight
Good luck
 
Another way to make sure you're hitting the apex is to apply sharpie to the secondary bevel. If the stone removes all of the sharpie when you make a pass you're good if not, reapply and adjust your angle.
 
bucketstove said:
You're microbeveling and your angle is too small to reach the apex
Try increasing the angle from 25dps to 30dps or 40dps or even 45dps

If that doesn't get sharper in under 10 strokes,
you're going to have to work on the edge bevel (20dps) with coarse stone ... some 60-300 strokes ought to do it , then microbevel at increased angle like you've been doing (this also cuts off the burr)

Here they're talking about ka-bar having 20dps to 30dps edge http://www.bladeforums.com/forums/showthread.php/966474-Sharpening-the-Ka-Bar-USMC

If you're trying to microbevel, that is a few strokes at elevated angle to get it sharp, it has to be elevated enough to touch the apex ... if the edge bevels is 20-30dps you need at least 30-40 dps to touch apex

Before I figured stuff out, I was trying to microbevel at 25dps when the edge was at at 20dps but I hadn't raised a burr yet ... not enough time on the coarse stone to where microbeveling would get it sharp in under 10 strokes

raising a burr is one way, another is looking for reflection with flashlight
Good luck
Click to expand...


This seemed to do the trick. Still not ideal, but it definitely has an edge on it now.

Thank you very much.
 
Okay, I'm at my whits end here.

Raising the angle seemed to work, but after a few uses it was completely without an edge again.

I've tried everything to sharpen this knife and it still won't cut.

I traced the bevel with a sharpy, used angle guides, and ran it across my belt grinder and It's still completely dull. Now when I say dull I mean it has the same cutting edge as pre-worked bar stock.

I've never had this much difficulty putting an edge on a blade. Not even this one. This is a new problem that's formed over the last few weeks and I'm boggled at what happened. For the most part I use the knife mainly for opening bags of pet food. It has seen some hard use early on, but not not in the last year or so.

Please knife guru's help me here. I'm almost to the point of throwing out one of my favorite knives because it just won't take an edge.
 
Very rarely it's the knife, I've been down that road before. It was my technique that was lacking. Do you have a Microscope to see the edge? That will tell alot more than us guessing. Also mentioned above are you forming a burr? Typically a microbevel shouldn't make it any sharper, just add to the longevity of the edge.
 
Depending on what you've done, you could have a variety of issues. Start by doing this: Try to reflect light off of the cutting edge. Look straight down on it, standing under a strong light. Angle the blade up and down, keeping the cutting edge facing you. Do you see a very thin line of light reflected back?

If so, the edge is dull, either because the edge rolled over on you after use, or it just never got totally sharp. Let's pretend that the edge has been weakened due to a large burr, overworked metal, or something else. I would personally cut that bad steel off by cutting directly into a stone. Yes, I'm saying to lightly drag the entire edge across a stone, as if you were trying to make a shallow cut directly down into the stone. I would do this 3 to 5 times, rather lightly. When you are done, the reflected light test should *very* clearly show light reflecting back. Because you just flattened the edge.

Then go through your sharpening routine again. You can use the reflected light to track your progress. As you thin the edge, at some point you'll see the reflection start to get smaller. Then it will go away completely. At this point the edge is probably pretty sharp.

If you are using burr sharpening, make sure to finish off with a good number of back and forth strokes to try to eliminate the burr as fully as possible. This can be one of the trickiest parts of sharpening. But a burr free edge that's truly sharp is worth the effort.

Good luck to you!

Brian.
 
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