Yet another DMT Diasharp question.

CrimsonTideShooter

CrimsonTideShooter

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Oct 23, 2010
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I have been advancing quite quickly with free hand sharpening, but one thing continues to baffle me. With any other stone this isn't a problem. (japanese water stones, spyderco profile set)


When I am sharpening with my DMTs, no matter how I position the blade I cannot sharpen the heel of the edge. I consistently cannot form a burr on the first 1/4 t0 1/2 inch of the blade. It almost seems like the edges of my C and EF DMT stones are raised, so that I am only sharpening on the center of the stone.

I can tell that I am only hitting the center of the stone because near the edges of my DMTs the diamonds are much more aggressive, meaning I haven't yet worn them in. Also, the very edge (maybe 1/8 inch) of the stones seem to be completely smooth, there seems to be no diamonds at all at the very edge.

I hope someone can help me out. Not being able to sharpen the whole length of the edge is keeping me from loving these stones. And yes, I have tried different blades. Thanks everyone.
 
Although I've previously illustrated my lack of freehand skills, the few times where I have done it, I have encountered the exact same problem. I will mark the edge with a sharpie, and consistently the heel of the blade will be the only part left untouched. This is with Smith diamond stones, so it might not be a product flaw with DMT. So you're definitely not alone here.
 
Almost without exception, every knife I've ever sharpened is always more difficult to finish in the area near the choil. Most of it is due to the grind of the blade being a bit 'thicker' there, which almost always makes the factory edge more obtuse. When the blade is positioned on the hone at the 'proper' angle for the rest of the edge (almost always lower/more acute), the more obtuse portion near the choil will not contact the hone. More likely, the shoulder of the bevel there will be in contact. This means it takes a LOT longer to finally grind away enough of the shoulder to bring the edge angle in line with the rest of the blade's edge. The choil is an an area that almost DEMANDS close, frequent inspection under magnification, so you can see what progress you're making there. When you finally get it there, the thicker steel in that portion of the blade will also give you a wider bevel, to some degree. Generally the same thing applies near the tip, which is also usually thicker, but easier to get done because you can simply lift the blade to make contact. Obviously, lifting the blade won't work at the other end, so you've just got to keep grinding away at the shoulder, until you work it down to flush contact at the edge.

Bottom line, PERSIST at it, and keep watching your progress with a magnifier. It'll take a while, so just take a deep breath, relax and press on.
 
OWE, I had initially thought that was the problem also. So I set the bevel on my M4 manix 2 with the EP, then went to the stones to see how it did then. Same thing, I was matching the existing bevel perfectly for most of the blade, but the last half inch or so at the heel wasn't being touched. No matter how I positioned the blade, it just wouldn't touch it.

I'm almost starting to believe that the edges of the stones are a little bit higher than the center. That's the only explanation my simple mind can think of?!
 
CrimsonTideShooter said:
OWE, I had initially thought that was the problem also. So I set the bevel on my M4 manix 2 with the EP, then went to the stones to see how it did then. Same thing, I was matching the existing bevel perfectly for most of the blade, but the last half inch or so at the heel wasn't being touched. No matter how I positioned the blade, it just wouldn't touch it.

I'm almost starting to believe that the edges of the stones are a little bit higher than the center. That's the only explanation my simple mind can think of?!
Click to expand...

Maybe so. You might check it with a dead-flat straight edge (edge of a steel ruler, for instance) or against a piece of window glass. If the stone isn't flat, you'll see daylight in the gap between them.
 
Another thing occurred to me. If this doesn't apply, please disregard.

Assuming a sweeping, heel-to-tip stroke on your hones, the heel of the blade is only going to be in contact with the hone for a miniscule time (at the very start of the stroke, then it's off the edge). I've always had to make sure I kept the stroke directly perpendicular to the blade edge, specifically when working on the heel. If you're making a sweeping heel-to-tip stroke, the heel gets almost no time in direct contact, relative to the rest of the edge, which will sweep across a much wider portion of the hone. That translates into a lot less metal removed at the heel on each pass, which would definitely impede forming a burr in a timely fashion.
 
My 1 cent here (not good enough at sharpening to throw 2 cents...)
David, I guess your last thought might be the answer. I thought about the very same thing when I was sharpening freehand for the first times.
The very first part of the blade gets half the contact with the stones (or with sandpaper) than the rest of the blade, and that's what makes it harder to sharpen.
Depending on the stroke movement, a very similar thing can happen to the tip actually, but my guess is that people generally sharpen the very tip as an isolated section. The "anatomy" of the knife doesn't really allow you to do the same with the opposite part of the blade (the choil side). So I guess that's why.
Also, that part of the blade is (on average) less involved in cutting tasks. Nonetheless, it would be nicer to see the whole blade with the same angle; I guess that, depending on the geometry of the blade, this can be more or less evident.
:cool:
 
Obsessed with Edges said:
Another thing occurred to me. If this doesn't apply, please disregard.

Assuming a sweeping, heel-to-tip stroke on your hones, the heel of the blade is only going to be in contact with the hone for a miniscule time (at the very start of the stroke, then it's off the edge). I've always had to make sure I kept the stroke directly perpendicular to the blade edge, specifically when working on the heel. If you're making a sweeping heel-to-tip stroke, the heel gets almost no time in direct contact, relative to the rest of the edge, which will sweep across a much wider portion of the hone. That translates into a lot less metal removed at the heel on each pass, which would definitely impede forming a burr in a timely fashion.
Click to expand...

This, and or lower the position of the handle to make better contact in that area. When you sharpen only a very small section of the edge makes contact.
 
If you don't mind adding a sharpening notch, you'll be able to get the whole edge.

The following vid is a pretty good explanation. Look to around 4:30 to see a macro. Just to let you know, this is not my vid.

[youtube]VMvE-b4259A[/youtube]
 
That happens to me as well. IMO since most edges are factory finished using belts, there's almost always a tendency for the edge to have a slight recurve either just above the choil, or if there's no choil cutout, then it'll be right at the base . On all of my solid stones I've lapped a radius into the edge of the stone down one side so when I have to work on a knife with this characteristic its no problem. Ultimately it keeps me from using my diamond stones with any frequency.

Once I started shaping my stones this problem went away.
 
Although i'm somewhat new to this forum, and hardly ever post, I will add this. As Obsessed With Edges said, when u sharpen, very little time is spent on the stone at the heel of the knife. You have to really work the heel of the knife a lot back and fourth. I, as well use the DMT stones, from C, F, XF, and 3 Micron. I have no trouble at all with getting the heel to look like the rest of the blade. You just have to work it much more.

I checked 3 different knives when reading this post and used a caliper to measure about 1/4 inch in from the edge, and all of them were almost 30thousand's in thickness at the heel and about 1 inch up from there toward the tip. So on my knives at least, the measurements and blade thickness seem to be about the same. I measured Spyderco's, and Case, and Hen&Rooster's.

Got my first knife when i was either 8 or 9 years old, grew up on a Dairy and Hog farm, and casterated many pigs and calves with my knives, and countless thousands of bales of hay string, so they had to be sharp even way back then. My daddy told me to keep it sharp, and said the heel was just as important as the tip. So I've been sharpening knives now for just about 50 years. Got my DMT stones couple years ago, and they made it so much easier. After I go through the 4 stones , I finish off with a Paper Wheel, with ever so light pressure, with Green compound. (and i mean very , very light pressure). My knives are very sharp. I never move on to the next stone till I can absolutely shave hair with the Course, and so on.

I hope this helps, just stay persistance, and it will happen, because most likely, it's not the stones falt. Good Luck!

Regards,
John
 
When I sharpen, I spend some time at the flat part toward the heel before I begin the curve to ensure that equal time is spent along the edge. Also, I pull the knife to the side during the stroke, perpendicular to the length of the stone, staying on the heel, in order to get all of the flat part of the edge. This is opposed to doing a stroke on the rear-most part of the flat part and then going into the curve right away.

One problem, though, or at least one that I've had is that the diamonds on the edges of the DMT stones come off or wear away very quickly. This is precisely the reason that the flats of my knife edges don't get that sharp, either. I assume that this is a problem with diamond stones because I don't have the same problem with stones where the solid block is made of abrasive material.
 
Yes, it is the individual technique and how that portion of the knife is worked on the stone. I start at the heel/choil and began working the blade and don't move toward the tip until a burr it reached at the this area first. Then proceed on toward the tip. Yes, most seem to be some what thicker in that area and it could be not the metal but the grind. DM
 
hold the knife diagonal in relation to the stone and use the corner of the stone, no problem to isolate the choil area and give it some extra attention. make sure the stone is raised enough to get clearance with the knife from the table.
Also, in my experience, the choil seems to be where the grinding starts first for knife makers/manufacturers. I find that sometimes there is less steel there and therefore it takes longer to reach the edge/bevel until the area further away from the choil is also thinned down.
 
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