Help Needed: Finishing an Edge

[The Burgh]

Have done ~ 20 kitchen and field knives on my KME. Generally, very pleased with the tool.

However, I consistently have two challenges:

1.) As I get down to fine and finer grits, and before stropping, I find that the sharpness (nail test, finger test, paper cutting, etc.) decreases. Yes, I do sharpen to "sharp" at every grade stone before moving onto the next finer grade. Do I need to reduce the angle for every succeeding stone (by as little as 1 degree) as I move up, in fineness, in order to preserve the last sharpness apex?

2.) I notice that when the knife is finished, I (and everyone I sharpen for, all knife novices) first examine the look of the edge. My edges are "wavey" on the surface, not a flat smooth surface. (Here I am referring to the surface of the edge, not the line of the bevel.) I suspect that the wave is produced by both the repeated 2" opposing grind and the changes of hand pressure, but I use a very light "weight-of-the-stone" pressure. I have been trying to remove the wave with 1500 grit sandpaper by hand, but then oftentimes remove the sharpened apex.

Can any of you kind BFers suggest some remedies here? Thanks in advance!

 

[HeavyHanded]

First one, make sure you are going to a burr and removing it. Changing the angle in this case will not effect the result as I understand your question. If the edge is cleanly ground to the apex at every step, it will behave differently on some cut tests, but should still be "sharp", catching on fingernail, paper cutting etc.

As you guess, the wave you are seeing is from crossing the abrasive on the bevel. If you use the same mechanics for every pass, the grind lines will lay in with a uniform pattern, by crossing the scratch pattern, you create a surface effect that will be visible.

 

[fvdk]

Which stones do you use? the ceramic and Arkansas stones vary a lot in thickness which should be compensated for.
This could be one of the reasons for inconsistent results with the KME. Another reason might be that the knife is securely clamped and tilts while sharpening.

Here are the measurements of my KME stones

White Hard Arkansas 6.91 mm
Black hard Arkansas 6.66 mm
White ceramic 6.55 mm
Pink ceramic 6.21 mm
Brown ceramic 5.70 mm
Black ceramic 5.54 mm
Kangaroo strop 5.55 mm
Diamond stones all 4.81 mm

 

[The Burgh]

Really getting good help! Thank you to all!

Forgot to mention up in the original post that I use an Angle Cube. However, the flex/wiggle in the KME clamp may be play. I'll try to tighten the spring a bit more.

Also suspect the above "cross-hatching" diagnosis to be in play. Unfortunately, with the single horizontal pivot pont point on the KME, there may be no cure. I already move the clamp at least once on every 3 inch blade, more often on longer blades.

 

[fvdk]

Also suspect the above "cross-hatching" diagnosis to be in play. Unfortunately, with the single horizontal pivot pont point on the KME, there may be no cure. I already move the clamp at least once on every 3 inch blade, more often on longer blades.

Now that is one thing you should not worry about, check this thread http://www.bladeforums.com/forums/showthread.php/1339022-angles-on-clamp-style-devices

 

[The Burgh]

I'm trying, with weak results, to explain this physical action: As I sweep across the arc which intersects the straight blade edge, I am (unsuccessfully) intersecting the edge at different, non-uniform angles. Some of my sweeps are perpendicular to the edge, some are angular or semi-circular.

 

[HeavyHanded]

The key is to sort of de-focus, sort of like taking in the entire sheet of paper as you write (unlined) to to keep it all squared up as you go. You need to be aware of the mechanical sweep across the edge. I suspect with more practice this will become 2nd nature.

 

[The Burgh]

So, should every pass be as perpendicular as possible to the edge (with no curvey, arching motions while "sawing?"

 

[115Italian]

The basics- maintain a consistent angle. You must get a burr to form. Once you get down to a medium grit, you have to go until you smooth out all the unevenness caused my the courser stones. Take your time. Be consistent. Learn from your mistakes. Youll get it.

 

[HeavyHanded]

So, should every pass be as perpendicular as possible to the edge (with no curvey, arching motions while "sawing?"

Not at all, it can be curved, but should be the same curve (or close) every time. Even with a guided system you cannot maintain 100% perpendicular. You can pick up the hone, set it down on a start point, and make consistent passes end to end. Try to adopt a systematic method of moving the hone. The arc should be similar every time, start to finish, overlapping as you go. Stop often and study your results. Keeping in mind this is cosmetic and likely unrelated to any performance issues.

 

[rutcrazed]

If I understand your dilemma correctly, I had that happen to me also. I use an EPP. I found that the last two stones I was using were dished slightly. I flattened them and problem solved.
If I have misunderstood the problem ignore me and carry on.

 

[fvdk]

Even with a guided system you cannot maintain 100% perpendicular.

Yes you can for the straight portion of the blade, no matter how long it is. The angle will only change on curved blades or on the curvature of the tip.

Why this is and more prove of this can be read in the thread I referenced to in post #3

But here are 4 pictures which show that at either point on the blade and also at the maximum swing of the arm, the angle stays the same even when you swivel the blade down left or right.

So to answer two other questions of the OP:
The only reason to move the blade in the clamp would be if it is longer than the side-to-side reach of the stone.
It might make a difference for the scratch pattern or the burr but for the angle it does not matter if you rub the stone up and down, in a circular motion, edge leading or edge trailing.

Frans

 

[HeavyHanded]

Yes you can for the straight portion of the blade, no matter how long it is. The angle will only change on curved blades or on the curvature of the tip.

Why this is and more prove of this can be read in the thread I referenced to in post #3

But here are 4 pictures which show that at either point on the blade and also at the maximum swing of the arm, the angle stays the same even when you swivel the blade down left or right.

So to answer two other questions of the OP:
The only reason to move the blade in the clamp would be if it is longer than the side-to-side reach of the stone.
It might make a difference for the scratch pattern or the burr but for the angle it does not matter if you rub the stone up and down, in a circular motion, edge leading or edge trailing.

Frans

I'm not talking about bevel angle, am referring to the grind path relative to the edge - OP is noting cosmetic/visual effects in the scratch pattern. For it to be perpendicular the entire length, you'd have to move the tool along on the clamps so your contact point stayed dead even with the mast. As the arm contacts further from this perpendicular point even with the mast, the grind pattern is going to shift, sort of like the vanishing point in a drawing.

To beat this effect without moving the tool in the clamps (and you can), will require changing how the hone is moved through the guide - you have to look past the hone and imagine the scratch pattern you're making with each pass - the angle of the hone will change, sort of like a car doing a fishtail through a turn. Instead of moving it back and forth in a line with the mast, you have to consciously move it back and forth relative to the edge. The scratch pattern could be swept at any steady angle relative to the edge, but it won't happen without intent.

 

[fvdk]

I'm not talking about bevel angle, am referring to the grind path relative to the edge

OP wrote "wavey" on the surface, not a flat smooth surface"

Perhaps I am interpreting it wrong but I think he is noticing an uneven edge and not talking about the direction of the scratch pattern.
Also because in another thread the asks....

How far beyond the 2 edges of the clamp do you grind the blade (before repositioning the clamp to preserve some semblance of angle uniformity along the entire edge?

 

[HeavyHanded]

OP wrote "wavey" on the surface, not a flat smooth surface"

Perhaps I am interpreting it wrong but I think he is noticing an uneven edge and not talking about the direction of the scratch pattern.
Also because in another thread the asks....

How far beyond the 2 edges of the clamp do you grind the blade (before repositioning the clamp to preserve some semblance of angle uniformity along the entire edge?

Maybe I'm interpreting it wrong - my assumption was a cosmetic issue, not an angle issue.

 

[The Burgh]

You guys are the best!!! Thanks for trying to help me walk through this.

Up in my original post, I asked two separate (but not necessarily unrelated) questions.

The second question has to do with cosmetics, and it is not that I see scratch lines. I see tiny, uneven surfaces. If I tried the read-print-in-the-edge-like-a-mirror test, the print would be distorted but not broken by scratches. Its as if each pass of my stone creates its own surface which is the very slightest bit different from the plane of the last and next passes.

As to angles, I thought that it was pretty well accepted that the increasing distance from the center of the clamp, i.e. reaching further and further from the edges of the clamp, will reduce the angle of the sharpening stone. That's what my angle cube tells me, that's what the larger edge at the blade tip tells me and that's what spawned my question in the other thread. I try to compensate for it by moving the clamp along the spine of the blade.

Most importantly, THANK YOU!

 

[fvdk]

As to angles, I thought that it was pretty well accepted that the increasing distance from the center of the clamp, i.e. reaching further and further from the edges of the clamp, will reduce the angle of the sharpening stone.

No, that is a widespread and persistent misconception.
Like I mentioned before, WHY it is a misconception is explained in the other thread I referenced in post #3

So you trying to compensate by moving the clamp along the spine of the blade might be part of your problem and not the solution.

Do yourself a favor and read the other thread or at least the conclusion. It will help you to understand and get better results.

Frans

 

[The Burgh]

"With ANY clamped setup, the real angle will decrease as the edge of the blade is moved further out in the clamp, away from the clamp's jaw."

That is a quote from that other thread, and it conforms to my weak retention of high school geometry. The uniform sharpening angle is only retained on a perfect arc as measured from the fixed pivot point. The straight/non-arched blade edge only intersects the arch at two points - at the distant ponts of the blade - or a single point, the center of the clamp.

Not intending to argue or debate here, just trying to get a better (looking) edge.

 

[fvdk]

Yes, when moved our further from the tip of the clamp, so deeper or less deep situated in the clamp, not sideways. You are quoting one sentence out of the whole thread while not understanding what is meant. You are also repeating arguments that are made and proven to be wrong in that same thread.

If you wanna do so and don't want to take the time to read it and understand why you are wrong than fine, that is your prerogative.

I am not going there again, all arguments and prove have already been made in the other tread and also in the pictures I posted above for that matter.

Frans

 

[The Burgh]

You're yelling!

I have read that thread, and it seems to focus on the depth of the blade in the clamp. That's not in play here.

Sorry your self-evident expertise is just not making sense to me, nor is it showing up in my use of the KME.

Oh well, onward and upward.