Can't form burr or get good edge with Sharpmaker

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postoak

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Dec 23, 2011
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I have a custom made 4" drop-point knife that I believe was made from salvaged L6 steel. I field-dressed four deer with it this season and afterwards noticed there were 3 or 4 chips in the edge so I sharpied the edge and removed enough of the edge to get rid of the nicks while attempting to keep the existing profile using a dry very course carborundum stone. I then smoothed the edge with a soft Arkansas oil stone.

Next I went to my Sharpmaker and went through the stones at 40 degrees using all four stones from diamond through ultra-fine.

So, at this point I had a not very sharp knife. It wouldn't cut hair, wouldn't push cut at all, wouldn't slice cut from the edge, and would slice cut only if I poked the point through the paper and pushed down fast.

I noticed that I was hitting the side of the blade away from the edge at one point, so I went to the 30 degree bevel and repeated the process. Then I repeated the process at 40 degrees. No change in sharpness.

At this point, I decided to follow jdavis882's system of using only one stone at a time to develop a burr. I attempted this with the coarse stone and the medium stone to no avail, and I mean I used many, many strokes. No burr. So where do I go from here?
 
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Chris "Anagarika";15539699 said:
Perhaps you're not hitting the apex? Don't move up from diamond until you hit apex on both sides.Try the sharpie trick to see where you 're removing metal, also check some tips on this thread:
http://www.bladeforums.com/forums/showthread.php/1350683-Sharpmaker

Also, it is good to read & understand sharpening basic from:
(Sticky on this subforum):
http://www.bladeforums.com/forums/s...hat-is-sharpening-a-knife-about-(2015-updates!)
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Agree.

You should be able to slice phonebook paper even after the diamond rods. If not, it makes no sense to progress thru the other rods until it can.

Using a Sharpie for verification is an essential step when using a system, especially for a first time, even more so when getting poor results.
 
Try the reflected light technique to examine the actual cutting edge:

Hold the blade with the cutting edge facing the ceiling. Stand under bright light. Now, angle the blade up and down. Angle the tip towards the ceiling. Angle it down towards the floor. While doing this, look straight down at the edge. You're looking for a reflection along the edge. If you can see a reflection, it's dull where the reflection is. The angling up and down is to give you different reflected angles and give you a better chance of seeing a reflection along the whole length.

I suspect you just haven't gotten all the way to the apex yet. If not, you'll probably see a reflection along some part of the edge, or perhaps the whole thing. You can use this test to tell when you *have* hit the apex. When the reflections disappear, you're very close to a sharp edge. It should form a burr shortly after the reflections go away.

Good luck!

Brian.
 
I HAVE been using the sharpie trick. It showed me getting all the way to the edge with the diamond hones, the first time around and I've gone through the entire process two or three times, using dozens of strokes instead of 20 AND THEN on top of that using jdavis882's method of grinding on one side only until a burr is achieved. Also, when I look at the blade edge-on, it is almost invisible, no shiny spots at all like on a dull knife.

This is why I wonder if some steels can't be burred. Perhaps it wasn't properly heat treated?
 
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In my experience, the higher RC the steel, the less burring it will undergo. This also combined with different abrasives - waterstones with a bit of mud or softer stones will tend to create a much smaller burr or almost none. On diamond rods I would expect to see a burr if the abrasive cut all the way to the apex.

To detect a burr I use two methods - a quick on the fly is to grind my thumb or finger tip hard across the edge traveling from the spine. Then do same to the other side. If one side feels even a tiny bit more catchy than the other I have a burr. The other method is for finish work - hold the blade close to your eyes with edge pointing down, strong overhead lighting directly above. Slowly rock the edge back and forth so light plays along the face - you can tilt it a bit as you go in either direction too. The burr will appear as a bright line just off the edge. This also a good way to see if the edge is truly ground all the way per bgentry (Brian) above.
 
postoak said:
I HAVE been using the sharpie trick. It showed me getting all the way to the edge with the diamond hones, the first time around and I've gone through the entire process two or three times, using dozens of strokes instead of 20 AND THEN on top of that using JD882's method of grinding on one side only until a burr is achieved. Also, when I look at the blade edge-on, it is almost invisible, no shiny spots at all like on a dull knife.

This is why I wonder if some steels can't be burred. Perhaps it wasn't properly heat treated?
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The Sharpie method LIES frequently. The ink from the Sharpie doesn't stay put very well on steel anyway, and just a single pass can scrub it off, whether the edge is apexed or not, and whether any metal is removed with the ink or not. Look only for the burr to confirm the edge is apexed. The Sharpie can help in showing you're on the right track in progressing towards the edge, but it's never very reliable in proving it's been apexed; in fact, I'd say it never does. The burr is the proof.

When it looks as if the Sharpie ink is gone, that's the time to take each pass once at a time, looking very closely for any signs of a burr after each pass. With some steels, even tiny burrs can/will break away pretty fast after they form, so you have to watch for it very intently.


David
 
Huh, I looked at the edge under bright sunlight with a 10x loupe, and I saw many small reflections - spaced. It almost looks like tiny chips in the blade. Remember, this blade chipped during use. Is it possible this steel has impurities that chip out when exposed, thus making it impossible to ever get more than a micro saw-tooth blade?
 
postoak said:
Huh, I looked at the edge under bright sunlight with a 10x loupe, and I saw many small reflections - spaced. It almost looks like tiny chips in the blade. Remember, this blade chipped during use. Is it possible this steel has impurities that chip out when exposed, thus making it impossible to ever get more than a micro saw-tooth blade?
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Is more likely (maybe) that if it has very high RC value it might be chipping out on the diamonds and or ceramic abrasives as high RC carbon steel sometimes do. You could go back to the carborundum stone and use it with a bit of oil instead of dry. If you can get a clean (though somewhat coarse) edge off that stone, it may very well be the HT is high and diamond or ceramic won't be a good fit. You might also need to make the edge a touch less acute for what you're doing.

Is possible the steel is somehow defective but that should always be the last assumption.
 
postoak said:
...I sharpied the edge and removed enough of the edge to get rid of the nicks while attempting to keep the existing profile using a dry very course carborundum stone.
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Based on this statement... I'm guessing you now have way too thick an edge to use on the sharpmaker effectively, or even get the blade sharp. Removing nicks and chips while trying to keep the existing profile just moves the edge into thicker metal creating a thicker profile... and/or you probably also made the angle steeper because even though you tried to maintain the profile, it's easier to grind metal from the edge than the shoulder, so the majority of the time, the angle increases.

My .02, return to the coarse stone you used to remove the nicks, lower the angle (even flat if the knife will allow), and grind in a new relief or secondary edge. Then sharpen it. I'll bet then it'll get sharp. :)
 
Thanks for the suggestions.

Please note that I reprofiled using the 30° side of the Sharpmaker before going back to the 40° side.

Also, although I was *told* that this was probably L6 steel, it was pretty easy to grind away those nicks, and I've just been reading that L6 is notoriously hard to grind. So, maybe it is something else entirely.

HeavyHanded, what does HT stand for -- or did you mean to type RC again?
 
postoak said:
Thanks for the suggestions.

Please note that I reprofiled using the 30° side of the Sharpmaker before going back to the 40° side.

Also, although I was *told* that this was probably L6 steel, it was pretty easy to grind away those nicks, and I've just been reading that L6 is notoriously hard to grind. So, maybe it is something else entirely.

HeavyHanded, what does HT stand for -- or did you mean to type RC again?
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Not much chromium or vanadium in L6 composition to add a lot of hard carbides for abrasion resistance (which would make other steels 'hard to grind', like D2 with it's big chromium carbides or S30V/90V/110V, etc with heavy vanadium carbide content). High nickel content in L6 adds a lot of toughness (resistance to breakage by impact); but otherwise it doesn't seem much different than other relatively common carbon steels. L6 was apparently originally used for bandsaw blades, which would need the extra toughness and resistance to breakage. That toughness attribute alone, I'd think, should also make it a little (maybe a lot) more resistant to chipping, unless something's really wrong with the heat treat ('HT').

I'd be more inclined to assume the 'nicks' in the blade are likely dents/deformations, and not likely chipping. Deformation (dents, edge rolling) is far more common with edge damage on most knives, especially for a knife used as you'd described, for dressing out game (impact on bone, etc).


David
 
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I'm not sure anyone's asked a key set of questions here:

How are you checking for the burr? Have you detected a burr on another blade using this same method? Or another method?

Brian.
 
I have always checked for a burr just by feeling for it. I've never had a problem with detecting a burr on other knives.

Maybe I'm missing something, but it seems to me that the fact the sharpie shows I am removing metal right to the edge means that the blade isn't too thick for the Sharpmaker.

I am going to wait for more suggestions to come in before doing anything, but I'm disposed, at this point, to freehand with my soft Arkansas stone and check to see how the edge looks as per HeavyHanded.
 
postoak said:
Maybe I'm missing something, but it seems to me that the fact the sharpie shows I am removing metal right to the edge means that the blade isn't too thick for the Sharpmaker
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Not necessarily... post #7 already talked about this.

postoak said:
Thanks for the suggestions.

Please note that I reprofiled using the 30° side of the Sharpmaker before going back to the 40° side
Click to expand...

This doesn't necessarily mean that you did enough at 30deg. to make a difference. The sharpmaker... even with the diamond stones, is slower at removing metal than most people realize.

Maybe you could post some photos of this white whale... to see what it looks like?
 
I somehow missed post #7. Thanks for pointing it out to me. It's disappointing that the sharpie trick doesn't work as well as I thought.

Here are some photos:











In the first photo, see that wide bevel area under the S? That is where I started to reprofile using my Lansky set at 17°. I gave up because it was going to take forever with the coarse Lansky stone and with the clamp restricting how long a stroke I could make on the center part of the blade.

The scratches, well I put those on sometime in the last week of sharpening -- probably with the Lansky. The finer scratched area above and paralleling the spine of the blade was where there was some corrosion on the blade and I rubbed it with 0000 sandpaper.

Looking at the left side of the blade, there are two areas where the slight shines differently. These aren't visible when looking at the knife -- they appear only in the photo.
 
My 0.02 because my teachers have chimed in.
From the last picture, it seems to me not fully apexed at 30° sharpmaker.
I have seen this a few times during reprofiling that I had to remember again and again that most problem is not fully apexing on coarsest stone. It's quite frustrating when I thought I have reached there & went up to higher grit only to find out I haven't.

If you check the sharpmaker thread I linked, there's Magnanimous video showing that even for kitchen knife that's relatively thin, it took awhile to get to apex on diamonds. Your knife looks thick similar to my Endura Sabre Grind. My 30° including free hand bevel (take & give the wonble) is 3mm wide to give some comparison.
 
^^Lots of questions come to mind, in viewing the pics.

The ink shown on the bevels now, is it the original application of the Sharpie? If so, it seems as if some areas have only been minimally worked, with just slight ink removal near the edge. This may touch on what I'd mentioned earlier, about just a few light passes taking ink off, without really doing much significant grinding. If so, I'd bet the edge hasn't yet been fully apexed along it's full length; therefore the absence of a burr. In establishing a new edge, I'd expect to see new bevels that are somewhat wider and uniform along the full length of the edge.

Also, I'm curious as to what the edge & bevels look like with all the ink removed (as it existed before applying the Sharpie). I'm wondering if the ink may be hiding some things about the original bevels or grind, like a thick edge grind or uneven grind, or a rounding off of the bevels and/or edge (might indicate inconsistent hold of angle on the Sharpmaker and/or other stones used).

In the immediate near-term, I think I'd go back to using ONLY the diamond rods on the SM, and set some new, crisp and uniformly wide bevels with only those. I suggest the diamond rods because they have the best chance at establishing a brand new edge with minimal other complications. Create the burr there, and don't progress to anything else until there is a burr, and the edge is cutting like a crisp edge with a burr (meaning, it should cut easily through paper, perhaps with some snagging due to burrs present on the apex).


David
 
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