Can't form burr or get good edge with Sharpmaker

[postoak]

^^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. 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

That's not ink, it's just the lighting.

I found it confusing that the Lansky at 17 degrees was producing such a wide bevel, but it may be that that is what I will wind up with (or even wider if I profile with the 30 degree setting on the Sharpmaker).

 

[Obsessed with Edges]

That's not ink, it's just the lighting.

I found it confusing that the Lansky at 17 degrees was producing such a wide bevel, but it may be that that is what I will wind up with (or even wider if I profile with the 30 degree setting on the Sharpmaker).

That may be telling right there. If the bevels did appear unusually wide at that setting, that indicates the steel was (or is) very thick behind the original edge. The thicker the steel behind the edge, the wider the bevels will look at a given angle setting. If it's really that thick, odds are the edge will take a lot longer to grind back into shape, especially on a tool like the Sharpmaker, which would do the work very, very slowly (due to small working area of the hones, even limiting the speed of the diamond rods).

So far, everything I'm seeing and reading still suggests the new edge isn't fully apexed or thinned out enough to be close to good cutting geometry. Burrs will be much easier to form and more apparent when they do form at thinner geometry, most of the time.


David

 

[postoak]

Should I profile all the way to the edge at 30 degrees and then repeat at 40 degrees?

 

[cbwx34]

Yup, I think you got it now,,,, you're a long way from getting it done. The 17 deg. with the Lansky is the giveaway... 30 deg. with the Sharpmaker (15 per side) is going to hit even higher. I don't think you'll do it with the sharpmaker... not reasonably anyway.

That blade is probably a poster child for Murray Carter's (and others) method of thinning the whole blade to maintain a proper profile. You can do that on a big stone or belt sander. Then set your bevels and sharpen it. Do that, and I think you'd be a lot happier in how it performs on your hunts.

 

[postoak]

I could do the trick of attaching sandpaper to the Sharpmaker rods. What grit would you guys recommend? Is 60 too coarse?

 

[bucketstove]

I could do the trick of attaching sandpaper to the Sharpmaker rods. What grit would you guys recommend? Is 60 too coarse?

Probably too coarse
But if you're careful and
if you use it only to knock down the shoulders,
if you don't apex the edge or raise a burr,
then its probably not too coarse
if you're careful.

coarse side of sharpening stones is commonly between 120 and 220 grit
which is considered fine macrogrit for wood working



see pictures here where guy forms edge apex with #50 grit then takes it all the way up to sharpmaker grit level stones and goes beyond that, but you can still see the scratches from the 50 grit stone

sure they'll come out in the next sharpening or two three after that if he doesn't start with 50 grit again
its not a big deal really , but its usually not the goal when going to very high mirror polish finishes

 

[Obsessed with Edges]

Should I profile all the way to the edge at 30 degrees and then repeat at 40 degrees?

I'd stick with 30 only, and prove to yourself that the edge will burr and then cut well at that angle. That'll clear up any lingering questions of the steel being a problem, if it does well at 30. Thinning the edge to that degree might take a while, but the cutting geometry will be a whole lot better when it's done. After you've proven the edge performs as expected at 30, if you still want to add a microbevel at 40, that'd be the time to try it (carefully).


David

 

[Obsessed with Edges]

I could do the trick of attaching sandpaper to the Sharpmaker rods. What grit would you guys recommend? Is 60 too coarse?

If it were me, I'd just stick with the flats of the diamond rods. Unless the sandpaper is firmly stuck to the rods (with adhesive, double-stick tape, etc), it may lift/roll/move under the edge of the blade and introduce a whole new set of problems (edge rounding, more trouble forming burrs, etc).

The main limitation with the Sharpmaker is the small size of the abrasive working surface. No matter if diamond or sandpaper is used, it's still going to take some time (or a lot) on big jobs. At least with the diamond or CBN rods, there won't be any of the new problems generated as with trying sandpaper on a device that really wasn't made for it. Sandpaper works at it's best when it's used on a large, flat, smooth and hard backing (glass, stone, etc) with the paper firmly attached.


David

 

[postoak]

I attacked one side of the blade with the diamond hone last night. At 2000 or so strokes, I began to get a burr at the back part of the edge -- and had raised the bevel to where that section done with the Lansky no longer stood out. After 4000 strokes, I still only had a burr on the back 3/4". After 4000 strokes, I stopped counting strokes and switched to time measuring.

Here's a question -- the bevel width is increasing as I go forward on the blade, maximizing about 2/3rds of the way forward and then decreasing slightly to the point. I am sure this has something to do with blade geometry, but can't figure out what.

As you can see, there are more scratches on the side of the blade, so it probably wasn't the Lansky that put the first ones on there but rather the Sharpmaker -- perhaps I got careless on a few strokes and didn't hold vertical. As you can imagine, it's hard to keep your concentration after 4000-5000 strokes.

I'm also not happy with the way the bevel is wavy at the back, but don't know what I'm doing differently there.

 

[postoak]

BTW, those scratches look a lot worse in the photo than they do in real life -- but after I'm through sharpening, I will definitely want to try to smooth them out somehow.

 

[cbwx34]

I'm impressed with your tenacity.

From your photos, it appears to me that you need to rotate the knife (lift up on the handle) as you approach the tip.

Some of the uneven parts might just be related to different thicknesses in the blade itself?

 

[awestib]

Yup, I think you got it now,,,, you're a long way from getting it done. The 17 deg. with the Lansky is the giveaway... 30 deg. with the Sharpmaker (15 per side) is going to hit even higher. I don't think you'll do it with the sharpmaker... not reasonably anyway.

That blade is probably a poster child for Murray Carter's (and others) method of thinning the whole blade to maintain a proper profile. You can do that on a big stone or belt sander. Then set your bevels and sharpen it. Do that, and I think you'd be a lot happier in how it performs on your hunts.

2nd that! I would thin out the entire primary grind, for a small knife like this you can go down to less than .5 mm "before" sharpening. Yes, that is a lot of work but at the end, if the knife is even worth it (the steel etc.), you have a much, much better cutter and applying the secondary bevel is going to be a breeze, not to mention the maintenance!

 

[postoak]

What does that mean .5 mm? Are you referring to the thickness of the blade? I was going to forget about the secondary bevel and just stay with 30 degrees.

 

[Obsessed with Edges]

I'm impressed with your tenacity.

From your photos, it appears to me that you need to rotate the knife (lift up on the handle) as you approach the tip.

Some of the uneven parts might just be related to different thicknesses in the blade itself?

That's what I'm thinking too. On a lot of blades, as the edge sweeps upward through the belly portion, the steel gets thicker as the edge gets closer to the spine. That's assuming the primary grind is tapered from spine to edge, as most are. Assuming it's thicker in those edge portions, the bevels will widen as well, if the angle remains held at a constant value. That being said, I wouldn't worry about the appearance of the wider bevels; they are (to me) an indication of better cutting geometry behind the edge. With some refinement at higher grits, the bevels' edges can eventually be 'blended' into the upper part of the grind; convexing the shoulders of the bevels would do it nicely. And THAT'S a good use of sandpaper on a somewhat forgiving backing, like leather or a couple sheets of paper; works very well for convexing the shoulders of bevels alone, not really messing with the edge itself (keep the angle LOW to work the shoulders).


David

 

[Obsessed with Edges]

What does that mean .5 mm? Are you referring to the thickness of the blade? I was going to forget about the secondary bevel and just stay with 30 degrees.

For now, that's what I'd do also. You've got enough work on your hands right now. Over time, and at your convenience, some of the primary grind could be thinned down during some of your regular maintenance sharpening, IF you choose to. Just lower the angle to work a little higher on the shoulders of the bevels each time. Many of my knives get 'thinned out' this way over time; there's no rush to get it done, but it pays off down the road if you choose to pursue it.


David

 

[pondoro]

I think the waviness at the base is where you used the Lansky before.

 

[postoak]

A Makesharp is looking pretty good right now. I'll never reprofile with the Sharpmaker again.

 

[postoak]

Okay! I have finished reprofiling. It took, I'm guessing, about 8000 strokes per side.

The bevel I got on the other side looks quite a bit different.

I'm not getting the results some of you guys said, though, although it slices a little more cleaning though newspaper.

I'll now work through the other stones and the strop and see what I've got.

 

[postoak]

Still not decently sharp. I guess I am going to have to go through the process of developing a burr with the medium stone next.

 

[Obsessed with Edges]

Still not decently sharp. I guess I am going to have to go through the process of developing a burr with the medium stone next.

I wouldn't, if it's not yet cutting well off the diamond hones. There's not much to be gained in trying to make a new burr on the medium ceramic, if the edge isn't yet as sharp as it should be off the diamond. Per your earlier post, if the edge is cutting somewhat better in newspaper after the diamond, I'd first strop that edge as it is, and see if cleaning up the diamond-honed edge a bit on the strop will improve paper-cutting a little more. It may be that some rough burrs are inhibiting the cutting of the paper after the diamond. If you see even a little bit of improvement in stropping a bit after the diamond, that's a clue that a lighter touch & more careful refinement on the diamond hone could get the edge cleaner (of burrs) and closer to full apex. I'm betting it still isn't there yet, but maybe it's pretty close; may just need a lighter touch on the diamond to get it there.


David