Getting blade chipping while sharpening 154CM

SunOfAtom

SunOfAtom

Joined
Feb 26, 2014
Messages
193
I am still a fairly novice sharpener, but I would like to believe I have a good understanding of the fundamentals. I am using an oil stone set which starts with a coarse/fine India stone, then moves to Arkansas stones and ends with stropping. I am also using the DMT aligner tool until I can get consistent enough to go completely freehand.

I have had good luck sharpening 8Cr13MoV and VG-10, but I am having a hard time with the 154CM on my mini-Grip. While setting the profile (30° inclusive) on the coarse India stone, I noticed some really fine chipping along the flatter heel of the blade. They seemed small enough to try to grind out with the fine India stone, but after hours of working the stone, I could get them smaller but not completely remove them. Moving up to the Arkansas stones at that point did not help, and finally moving back to the coarse India stone just brought in new larger chips.

Any thoughts on what could be causing this? Is 30° just too acute for this blade? The heel seems slightly more obtuse than the belly, and I don't seem to have any chipping on the belly. I am currently charging the battery on the only camera I have that has a macro setting, so hopefully I can get a decent picture soon. I also have a new coarse crystolon stone coming this weekend, which may yield better results.

Thanks!
Dave
 
From personal experience it is possible to sharpen that knife to that angle. It may not be chipping you see, but the scratches meeting the edge (given that you saw that the finer stone did make them smaller). With either the DMT XX or XC I've seen something similar - it kind of sparkles when you hold it up to the light with a fully apexed edge. It's possible that the jump from the fine India to the Arkansas might be too large to erase the scratches from the fine India. Since you have the aligner tool anyway, you could try the DMT stones (XC, C, & F) and holder with it.
 
Thanks for the input, and hopefully these pictures will help. It is definitely chipping, and behaving differently than any other knife I have sharpened with this same process. The chipping also seems to just be at the heel of the blade, the rest looks normal. When looking at the problematic area, you can see dips where it has chipped away and sometimes little peaks where pieces stick out past the rest of the blade edge. I lightly pressed across one of these peaks and it flaked off, leaving a small dip. I assume these are pieces that have technically broken off, but are just barely connected at the base.

These pictures are after I went back to the coarse stone, which made the chipping worse. While I was able to make them smaller with the fine India stone, I could not completely grind them out. I spent around 7 or 8 hours with light pressure on the fine India stone including building and removing many fine burrs, but the small chips always persisted (or more likely, new ones were created).

mg_04.jpg


mg_01.jpg


mg_02.jpg
 
That looks an awful lot like fragments of a visible burr breaking off, as it should start to do when the burr becomes thin enough. In the pics, the hair-thin reflection seen running the length of the edge is what I'd expect to see, with a burr. If it is a burr, it's weakened steel already, and should be breaking off. Additional grinding with the coarser stones will just increase the width of the burr. Stropping with some black or white compound usually cleans them up pretty fast, more so if on a very firm strop.


David
 
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Going with a coarser stone, as you found, will more than likely increase the chipping if in fact those are chips as opposed to hunks of burr. I can't tell one way or another from your pics. My eyes not your pics. If your using the aligner move it back a bit more toward the thumb stud. Use a finer stone, whatever you happen to have, and work the chips out along with working the rest of the edge. Light pressure. De-burr frequently if need be. Are your stones relatively flat?
 
I am certainly open to other possibilities, but I am still thinking that these are chips and not just burrs. The previous photos were taken after returning to the coarse India stone. From there I ran the blade over a strop with black emery to try to remove any burrs. I then worked the blade on the fine India stone until I felt that I had a nice fine scratch pattern. At that point I could see that the tip and belly were nice and smooth, but the heel still had visible imperfections. I managed to get some close-ups by taking the pictures through my 10x loupe:


Heel:
zoom_heel.jpg



And for comparison, here is the belly:
zoom_belly.jpg



The way the edge is now seems to be as good as I am able to get it, no matter how long I spend building up and removing burrs with the fine India stone. I just can't seem to get the heel free of the imperfections, like the belly is. The stones I am working with should be nice and flat. I use plenty of oil, rotate and clean them regularly. This is also only an issue with this knife. I have very smooth edges on many different knives that have different steel.

I appreciate all the feedback. If you guys have any tests you would like me to run using my current equipment, I am happy to do so. Otherwise I seem to be at a loss as to what else to try.
 
Whether it's chipping or a burr, the steel is obviously weaker there. Harsh as this may sound after already sharpening, it may be be best to put the edge perpendicular to the stone's surface and draw the blade across it, to scrub off the weakened steel. Then re-bevel and see how the new edge holds up.

Before doing the above, you might try this scrubbing technique across the corner of a piece of hardwood, like oak; make several passes at pretty heavy pressure (5-10). If it's a burr (very, very thin and weak steel, and usually pretty ductile), that should scrub a lot of the weak stuff off, and/or fold the burr over. If the steel is actually brittle enough to chip, this technique may actually produce some obviously new and deep chips. Either way, it'll tell you what you need to know.

I don't recall Benchmade's 154CM being near that brittle, which is why I'm still leaning to a burr as the likely culprit.


David
 
Its a long shot, but since you can get the tip and belly nice, maybe the heel is somehow being worked on the corner of the stone - the handle is dropping somewhat. That would tear up the edge quite a bit, and easily cause problems that could look like what you have.
 
Removing what might be weakened-- whether by HT or who knows what-- steel sure makes sense to me.

I dropped a 154cm 520 from a height of a few feet once, landed hard tip-first on a rock. Expected a broken tip-- was totally surprised to find a mashed one. Upped my opinion of the steel's toughness, that's for sure!
 
Thanks David. I tried scrubbing the blade through some hard wood, which did not seem to create any new chips but did create a fine rolled edge. However, many of the existing imperfections were still several times deeper than this new rolled edge. Perhaps I am dealing with both stubborn burrs as well as chipping? I went ahead and dragged the edge across the stone, which I will admit was rather satisfying after all the frustrations that edge had caused.

I'll go ahead and start making a new edge, though I am considering making the angle a little more obtuse. I am wondering if I am just asking too much to get the angle this acute on the rather basic and limited stone progression that I have. Perhaps my results would be different if I had a nice range of diamond stones to work with.

Pjwoolw, I am curious why you suggest placing the clamp further towards the heel of the blade. I am new to the clamp and just assumed that getting it as close to center would help keep my angle as consistent as possible across the length of the blade. I have no idea if that actually matters though, and I am open to any input on positioning the clamp.

Thanks again!
Dave
 
HeavyHanded, when I am moving the blade across the stone, I do not let the end of the blade hang off the edge of the stone. In other words, I have the blade angled so that any part of the blade that is level with the stone is actually on the stone. Is that what you were asking?

position.jpg


Thanks!
 
SunOfAtom said:
Thanks David. I tried scrubbing the blade through some hard wood, which did not seem to create any new chips but did create a fine rolled edge. However, many of the existing imperfections were still several times deeper than this new rolled edge. Perhaps I am dealing with both stubborn burrs as well as chipping? I went ahead and dragged the edge across the stone, which I will admit was rather satisfying after all the frustrations that edge had caused.

I'll go ahead and start making a new edge, though I am considering making the angle a little more obtuse. I am wondering if I am just asking too much to get the angle this acute on the rather basic and limited stone progression that I have. Perhaps my results would be different if I had a nice range of diamond stones to work with.

Pjwoolw, I am curious why you suggest placing the clamp further towards the heel of the blade. I am new to the clamp and just assumed that getting it as close to center would help keep my angle as consistent as possible across the length of the blade. I have no idea if that actually matters though, and I am open to any input on positioning the clamp.

Thanks again!
Dave
Click to expand...

If you can see & verify some rolling of the edge, it's highly unlikely any true chipping (bits of steel fracturing out of the blade) is happening at the same time. The depressions in the edge would more likely be due to plastic deformation (dents), by impacting something on your hone (HeavyHanded's suggestion of the edge hitting the corner of the stone could do that). Edge rolling & denting happens if the steel is relatively soft (ductile); chipping happens at the other end of the hardness spectrum, if it's too hard (brittle). Very unlikely to see both at the same time, on the same edge.


David
 
ryxly, HT = heat treatment? Do you guys ever find that an initial reprofile or sharpening behaves differently than subsequent ones?

Thanks!
 
Obsessed with Edges said:
If you can see & verify some rolling of the edge, it's highly unlikely any true chipping (bits of steel fracturing out of the blade) is happening at the same time. The depressions in the edge would more likely be due to plastic deformation (dents), by impacting something on your hone (HeavyHanded's suggestion of the edge hitting the corner of the stone could do that). Edge rolling & denting happens if the steel is relatively soft (ductile); chipping happens at the other end of the hardness spectrum, if it's too hard (brittle). Very unlikely to see both at the same time, on the same edge.


David
Click to expand...

Ok, that makes sense. Another piece of information that is now seeming relevant is that this is the first knife I have sharpened after re-flattening the coarse stone. It was seeming like it was getting clogged and too smooth, so I initially tried flattening it on the back of a new ceramic tile. That did not seem to do much, so I moved out to some flat white concrete in our back yard. While I definitely smoothed out a large circle in the concrete, it did seem to bring out a nice new surface on the stone. I wonder if it possible that the stone picked up some small hard bits from the concrete which is what is denting the blade.
 
SunOfAtom said:
ryxly, HT = heat treatment? Do you guys ever find that an initial reprofile or sharpening behaves differently than subsequent ones?

Thanks!
Click to expand...

Sometimes there'll be some damaged (weakened) steel at the edge from the factory, if part of the edge overheated somewhat during grinding on a powered device. In such cases, a couple or three sharpenings will often remove the damaged steel from the edge, after which it holds up much better. The method I suggested earlier, of scrubbing the edge across the stone, is a commonly recommended treatment to speed up the removal of weakened steel from the edge.


David
 
Man, this blades all over the place. You shouldn't see a rolled edge from pulling it through wood. You shouldn't get chipping just from sharpening. Sounds like the H/t is bad but how would you get two different problems? I would say, too soft after heat treat or if ever H/t. Then when grinding getting too hot in spots and tempering while grinding in others. Or something.

Personally, I wouldn't be happy. Did you buy it new? If so, then maybe Benchmade would make it good. If not, after all the sharpening you've done I would guess not.

Get a course stone and grind until it doesn't chip anymore.

Oh, your good edge looks really good. So I'm sure it's not you. If that helps.......
 
Sorry SOA I misunderstood your use of the aligner. I had a different technique in my minds eye. Disregard my comment on the aligner placement. I do suggest you go freehand sooner than later though. I agree with HeavyHanded that the edge of stone catching that portion of the edge may be an issue.
 
Great pics! Can't think of much to add to what the others have said, but if you're not already doing so, swap the sides as you're sharpening before any burr might have a chance to get so large that removal could cause a problem. And, unless you have a way of actually measuring the edge, you may actually be more acute than 30° and would benefit from going a little more obtuse.
 
Obsessed with Edges said:
If you can see & verify some rolling of the edge, it's highly unlikely any true chipping (bits of steel fracturing out of the blade) is happening at the same time. The depressions in the edge would more likely be due to plastic deformation (dents), by impacting something on your hone (HeavyHanded's suggestion of the edge hitting the corner of the stone could do that). Edge rolling & denting happens if the steel is relatively soft (ductile); chipping happens at the other end of the hardness spectrum, if it's too hard (brittle). Very unlikely to see both at the same time, on the same edge.


David
Click to expand...

Well this appears to have been the issue. I scrubbed the coarse stone with a wire brush and then did a full resharpen of an AUS-8 blade, and had no issues. I left everything the same with the mini-grip as it was before (angle, clamp position, etc.) and so far I am not having the same issue. I am slowly building up the edge and it is uniformly smooth across the entire blade. It will take a while (this 154CM is hard stuff!), but I'll post a picture of the finished edge when I am done.

Lesson for me today? Invest in a proper stone flattening device rather than using the concrete method. Thanks for all the assistance everyone!
Dave
 
SunOfAtom said:
Well this appears to have been the issue. I scrubbed the coarse stone with a wire brush and then did a full resharpen of an AUS-8 blade, and had no issues. I left everything the same with the mini-grip as it was before (angle, clamp position, etc.) and so far I am not having the same issue. I am slowly building up the edge and it is uniformly smooth across the entire blade. It will take a while (this 154CM is hard stuff!), but I'll post a picture of the finished edge when I am done.

Lesson for me today? Invest in a proper stone flattening device rather than using the concrete method. Thanks for all the assistance everyone!
Dave
Click to expand...

Glad to hear it's apparently resolved. Sort of interesting, in the possibility of some foreign embedded grit on your stone, from the concrete or whatever.


David
 
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