Blade chipping during sharpening

[RedpentacleB]

When sharpening a Chicago Cutlery AC42 USA kitchen knife, on the SG250, I'm getting micro-chipping along the edge. I tried dressing the stone using the fine side, but that did not help. WM-200 is set for 15 degrees. I sharpened other knives before and after this and they sharpen as expected with no issues. Is this just crappy steel? Should I increase the angle? Any ideas?
Sorry for the photo quality, uploads are limited to 256K.
Thank You,
Red

[John_B]

Chipping is where the material fractures. This area is studied as part of fracture mechanics and it has a loot to do with the material in question.

In knives chipping can be caused by a number of things. Most common is striking the blade against something hard. This can happen when they are improperly stored or washed.
Chipping can also be caused by a microscopic flaw or chip(s) in the blade. These weak points will become failure points for larger fractures as the blade is sharpened. Another possibility is impurities in the steel which over time can become the origin of fracture points.

If I were to venture a guess without having the equipment to examine the chips at the microscopic level I would go with microscopic chips were present and the stress of sharpening caused them to fracture to the point where you can see them. You might be able to save the knife if you grind it back a bit to remove any preexisting flaws ans then sharpen it.

[cbwx34]

When sharpening a Chicago Cutlery AC42 USA kitchen knife, on the SG250, I'm getting micro-chipping along the edge. I tried dressing the stone using the fine side, but that did not help. WM-200 is set for 15 degrees. I sharpened other knives before and after this and they sharpen as expected with no issues. Is this just crappy steel? Should I increase the angle? Any ideas?
Sorry for the photo quality, uploads are limited to 256K.
Thank You,
Red

...if you grind it back a bit to remove any preexisting flaws ans then sharpen it.

I was trying to find a good link to describe it, but my google fu is off this a.m.  But to add to what john.jcb said... you can take the knife and run it 90° against the side of the wheel, (with the machine off), this will remove fatigued/damaged metal, and leave you with a fresh edge/metal to work with.

Kinda looks like some heavy grinding may have been done to this knife in the past?  If so, may be part of the problem you're seeing.

You might also add a couple of degrees to the AngleMaster (WM-200)... if the the blade is tapered from spine to edge, and you're setting the angle based on the side of the knife, you're actually sharpening at a lower angle than 15°... so add a couple of degrees to compensate.

Edit:  Basically like this...

[RedpentacleB]

Thanks. The blade does show signs of prior abuse, and next time I'll add a couple of degrees to the WM-200 when setting the angle. I appreciate the feedback.
-Red

[Herman Trivilino]

So you don't know if the chipping was there before you started sharpening, or were created by the sharpening process?

Inspect the edge with good light and a magnifying glass. Sharpen and see if the chipping gets worse or better.

If the sharpening process itself is creating the chipping, then I recommend you sharpen at a more blunt angle. It's poor quality steel.

On the other hand, if the chipping is reduced by sharpening, I recommend dressing the grindstone coarse and sharpen until the chipping disappears. Then you can dress the grindstone fine and sharpen again. Finish off with the leather honing wheel.

[RedpentacleB]

So you don't know if the chipping was there before you started sharpening, or were created by the sharpening process?

Inspect the edge with good light and a magnifying glass. Sharpen and see if the chipping gets worse or better.

The chipping shows up during grinding, if I continue grinding chips continue to show up. The stone is well dressed and trued. The picture of the chips is through a 15x loupe. There are deep scratches on the blade in the general area of where the chipping occurs which lends weight to the damaged blade theory. I'm new at this so just wanted to get some feedback. I have been picking up knives at yard sales to practice on. This is the first time I have encountered something like this.
Thanks!
-Red

[Herman Trivilino]

The chipping shows up during grinding, if I continue grinding chips continue to show up. The stone is well dressed and trued. The picture of the chips is through a 15x loupe. There are deep scratches on the blade in the general area of where the chipping occurs which lends weight to the damaged blade theory. I'm new at this so just wanted to get some feedback. I have been picking up knives at yard sales to practice on. This is the first time I have encountered something like this.

I have encountered it only once on a pair of cheap pocket knives. The only thing I could do was sharpen them at a very blunt angle, making them useless for all but the roughest of purposes.