Sharpening Question. Wavy Edge. What Am I doing wrong?

[Hattusa]

hi, I'm just learning sharpening free hand. I can get a knife decently sharp if the bevels are properly set already. But if I have to reset the bevels myself, I often get a wavy grind line. Look at the photo of a new Old Hickory knife I tried to sharpen. I'm using a XX coarse DMT stone. What am I doing wrong? Is it just not maintaining a constant angle?

 

[Jason B.]

Wavy throughout the length of the bevel or just that spot?

What angle are you grinding at?

Another problem and one you have no control over is how well the factory did the main grind. Sometimes you will find low spots in the grind and this will result in bevel height changes.

 

[Hattusa]

I'm not sure what angle. When I sharpen free hand, I'm really just eyeballing it. How do you determine the angle when you sharpen free hand? There are at least two spots, one higher and one lower. I'm wondering if I'm flexing the blade, since this Old Hickory has a relatively thin blade.

I read in another thread you posted about sharpening that you correct uneven factory bevel during first sharpening, how do you do that?

 

[Jason B.]

Just by holding a straight angle and watching where contact is made.

I don't use angles either, my angles are high, medium, and low

Using a low angle shows more imperfections in the main grind, something that I believe is your issue. Like I said earlier the thickness variations in the FFG are probably to blame. You grinding straighter lines than the factory.

 

[richard j]

you might want to lay a straight edge along your blade just above the edge and see if the blade has an uneven grind to it. i have seen knives that have a valley 2" from the plunge line, which is the same width belt the factory used to grind the blade. i had a guy bring me a knife once and you could sight down the side and see a valley from the spine down to the edge. when i sharpened the edge, it had a thin section where the valley was at. from your picture thats what it looks like to me.

 

[crbauhs]

Just by holding a straight angle and watching where contact is made.

I don't use angles either, my angles are high, medium, and low

Using a low angle shows more imperfections in the main grind, something that I believe is your issue. Like I said earlier the thickness variations in the FFG are probably to blame. You grinding straighter lines than the factory.

Not that I have near the knowledge of yourself but I agree. Alot of times because we are taking our time we will grind suprisingly even straight edges and when that happens, your waves, then the blade itself wasn't ground flat. It has portions of the blade that are thicker and thinner. Happens more often then you would think of cheaper made knives.

 

[SteelSnob]

It pays to listen to a knifemaker. I'll bet my bottom dollar he knows what he's talking about.

 

[HeavyHanded]

hi, I'm just learning sharpening free hand. I can get a knife decently sharp if the bevels are properly set already. But if I have to reset the bevels myself, I often get a wavy grind line. Look at the photo of a new Old Hickory knife I tried to sharpen. I'm using a XX coarse DMT stone. What am I doing wrong? Is it just not maintaining a constant angle?

Three things come to mind, not including the aforementioned possibility that the main blade grind is uneven.

First, you might be loosing some contact with the flat of the stone and digging in with the outside corner. It's a lot easier to feel when this is happening with just about any other type of grinding material. The coarse diamond stones can mess up an edge bevel with just a few errant passes.

Second, you might just be loosing your bevel angle as a result of how you're holding the knife during the stroke. I (and a few others) noticed from knifenut1013's recent photos in another thread, that he appears to be running the edge somewhat less than perpendicular across the stone. I do it this way too (nearly at a 45 degree angle in my case), it puts more of the knife surface into contact with the stone during each pass and provides a better feel for when the angle is changing unintentionally. I also believe it results in a more refined edge than running the blade perpendicular to the grinding direction (all other things being equal).

Third, if the blade has any flex to it, you might be applying uneven pressure during each pass causing the blade to deflect into the stone in some places.

FWIW I remember having that exact condition crop up on my first few attempts when I made the switch to diamond bench stones. They are positively merciless if your technique isn't pretty consistent. They are the best, well worth figuring this one out. You might want to switch to some cheaper knives till you get it pegged.

 

[THG]

I can see from your bevels that you aren't holding the proper angle. You are going too steep and grinding the shoulder. When you sharpen (assuming you are not trying to change the angle) you should sort of be pushing the edge into the stone. When you do that and then go on to continue your stroke, you will feel some resistance, and this will tell you that you are sharpening the edge. It may be a bit harder now since you have varying bevels.

Personally, I use a DMT Aligner clamp to set my bevels

 

[Jason B.]

Pinch your fingers together just above the bevel and run them down the blade. I can see the dip from your picture and when you run your fingers down the blade you will be able to feel it.

Its the same issue you see here

 

[Hattusa]

thanks to everyone for the advices. I placed a straight edge against the blade, can't really see any imperfection. But when I pinched my fingers above the bevel and ran them down the blade, I do feel a slight depression at the spot where the bevel line dips.

There are definitely problems with my technique as well. I figure Old Hickory knives are good to practice on, they don't come much cheaper. Maybe I'll get an aligner guide too just to get myself familiar with the angles.

 

[THG]

Maybe I'll get an aligner guide too just to get myself familiar with the angles.

This tool is how I learned the mechanics behind sharpening. Use it as a set of training wheels. Let it teach you how you should be moving your hands and the motion it takes to grind an edge. Of course, the goal should be to not be dependent on it.

 

[richard j]

you dont really need the straight edge to see the dip in the blade. thats the first thing i noticed when i seen your pictures. from your second picture, you're doing a good job sharpening. maybe get another knife without imperfections in the grind and practice on that.

 

[Alberta Ed]

Try using an angle guide -- I have an ancient Buckmaster -- but DMT also makes a good one. It clamps on the back of the blade and helps to maintain a consistent bevel.